Eight-year report of stepwise excavation procedure outcomes in a US academic setting.

Transcription

1 University of Iowa Iowa Research Online Theses and Dissertations Summer 2014 Eight-year report of stepwise excavation procedure outcomes in a US academic setting. Paula Marcela Ortega Verdugo University of Iowa Copyright 2014 Paula Marcela Ortega Verdugo This thesis is available at Iowa Research Online: Recommended Citation Ortega Verdugo, Paula Marcela. "Eight-year report of stepwise excavation procedure outcomes in a US academic setting.." MS (Master of Science) thesis, University of Iowa, Follow this and additional works at: Part of the Other Dentistry Commons

2 EIGHT-YEAR REPORT OF STEPWISE EXCAVATION PROCEDURE OUTCOMES IN A US ACADEMIC SETTING by Paula Marcela Ortega Verdugo A thesis submitted in partial fulfillment of the requirements for the Master of Science degree in Operative Dentistry in the Graduate College of The University of Iowa August 2014 Thesis Supervisors: Associate Professor Deborah S. Cobb Associate Professor Sandra Guzmán-Armstrong

3 Copyright by PAULA MARCELA ORTEGA VERDUGO 2014 All Rights Reserved

4 Graduate College The University of Iowa Iowa City, Iowa CERTIFICATE OF APPROVAL MASTER'S THESIS This is to certify that the Master's thesis of Paula Marcela Ortega Verdugo has been approved by the Examining Committee for the thesis requirement for the Master of Science degree in Operative Dentistry at the August 2014 graduation. Thesis Committee: Deborah S. Cobb, Thesis Supervisor Sandra Guzmán-Armstrong, Thesis Supervisor Deborah V. Dawson Justine L. Kolker John J. Warren Ma. Marcela Hernández

5 To my amazing husband, for his unconditional love, constant encouragement and support on all my dreams. ii

6 ACKNOWLEDGMENTS I would like to express my gratitude and appreciation to my two mentors for their support and appreciated help in this project. To Dr. Guzmán-Armstrong for her guidance, great enthusiasm and time in this project. To my graduate director, Dr. Deborah Cobb for her clinical guidance, kindness and continual support during my entire program. Second, I would like to thank Dr. Deborah Dawson for her expertise and dedication to this project. I also thank to Derek Blanchette for his valuable help in the statistical analysis of the data. Special thanks to dental informatics, especially to Ron Roskam for his amazing assistance on the data collection. This thesis would have not been possible without his effort. I would like to express gratitude to Dr. Justine Kolker for her appreciated feedback and for sharing her wisdom with me. I also express my appreciation to Dr.Warren for his guidance, feedback and for taking his time to answer all my questions. I thank to Dr. Marcela Hernandez for her inspiring teaching about caries removal. Working with her and Dr. Guzmán-Armstrong truly heightened my interest in this topic. Thank you to all my brilliant committee members for guiding me and sharing their knowledge with me. Besides I would like to thank to faculty, staff and my classmates of the Operative Dentistry department, thank you to everyone s support! Special appreciation to my friend and colleague, Dr. Natalia Restrepo, for her friendship and encouragement during this process. Finally, I thank to my parents because they inspired me to be dedicated to learn more and to my love, Pablo, for understanding my passion on this research. iii

7 TABLE OF CONTENTS LIST OF TABLES... vii LIST OF FIGURES... xi CHAPTER I INTRODUCTION...1 Purpose of the study...3 Clinical Significance...3 CHAPTER II LITERATURE REVIEW...5 Dental Caries Disease...5 Definition of Dental Caries Disease...5 The carious process...6 Pathogenesis of the Dental Caries...7 Classification of Dental Caries Disease...10 Clinical dental caries classification:...10 Classification based on location...10 Classification based on cavitation status:...11 Classification based on activity status:...11 Classification based on caries experience the World Organization system...12 Classification based on severity or depth ICDAS system...12 Classification based on radiographic evaluation...12 Classification based on chronology...14 Early childhood caries (ECC)...14 Histo-Pathology of Dental Caries:...14 Enamel changes during caries progression...14 Polarized light microscopy (PLM)...15 Scaning electron Microscopy (SEM)...16 Carious lesion progression in dentin...16 Tertiary dentin formation...17 Zones of Dentin Caries:...17 Initial Pulp-dentinal complex reactions to caries...18 Deep carious lesions...22 Deep carious lesion definition...22 Deep carious lesion classification based on severity:...23 Closed and open cariogenic ecosystems:...24 Closed ecosystem...24 Open ecosystem...24 Deep dentin carious lesion classification based on activity:...24 Slowly progressing lesions...24 Rapidly progressing lesions:...25 Complete caries removal technique:...26 Definition of complete caries removal technique...26 Pulp exposure risk secondary to treating deep carious lesions...27 Improved understanding of deep carious lesion...28 Incomplete Caries Removal Approaches to treat deep carious lesions:...29 Indirect pulp treatment (IPT):...29 Stepwise excavation...30 iv

8 Difference between indirect pulp capping and stepwise excavation procedure...31 Partial Caries Removal...31 Ultraconservative approach...31 Stepwise excavation approach literature and background...32 Stepwise excavation technique definition...32 Stepwise excavation technique purpose...33 Stepwise excavation technique description...33 Stepwise excavation studies and randomized clinical trials...34 Other conservative caries removal techniques and further research...41 Need of further randomized clinical trials...44 Summary of Literature Review...45 CHAPTER III MATERIAL AND METHODS...47 Overview of methods...47 Main Research question...47 Sub-questions...47 Main Purpose:...48 Secondary Purposes...48 Main Expected Finding...48 Specific Expected Findings...49 General Objectives:...49 Specific Objectives...49 Definition of Variables...51 Dependent Variable:...51 Independent Variables...51 Operational Definitions...52 Study design...54 Sample Size:...55 Population:...55 Inclusion criteria:...55 Pilot Study Objectives...55 Pilot Study...56 Institutional Review Board Information (IRB)...57 Data Extraction Methods...57 Statistical Methods...60 Selection Methods for Logistic Regression Model...62 Forward selection...62 Backwards selection...62 Stepwise selection...62 CHAPTER IV RESULTS...64 Overview...64 Data filtering...64 Basic Descriptors...65 Basic descriptors per patient...65 Description of the study population Tooth Specific Study Variables per Patient...68 Basic descriptors for patients divided by Re-entry status...69 Bivariate Analyses...74 Bivariate Analyses involving Categorical Covariates...74 Bivariate Analyses involving Quantitative Covariates...75 v

9 Logistic Regression Modeling of Re-entry Status...77 Clinical outcomes...81 Clinical outcomes using one SWP per patient...81 Main Finding...83 Specific Findings...83 General Objectives...83 Specific Objectives...84 Summary of results...85 CHAPTER V DISCUSSION...87 Background information...87 Main findings...87 Main Limitations...95 Main Strengths...96 Summary...98 Future directions...99 CHAPTER VI CONCLUSION REFERENCES APPENDIX A. INDEPENDENT VARIABLES APPENDIX B. PROCEDURES CODES APPENDIX C. IMPORTANT GUIDELINES FOR SWP APPENDIX D. SUMMARY DESCRIPTIVE ANALYSIS BY PATIENT APPENDIX E. UNIVARIATE, BIVARIATE AND LOGISTIC REGRESSION ANALYSIS BY PATIENT Basic descriptors per patient Basic descriptors for patients divided by re-entry status Bivariate Analysis Logistic regression modeling Supporting figures for Statistical Analysis vi

10 LIST OF TABLES Table 1. Diagnostic levels of dental caries measured using the International Caries Detection and Assessment System (ICDAS)...13 Table 2. Radiographic classification of caries Table 3. Complete caries removal technique advantages and disadvantages Table 4. Distribution of the number of stepwise excavation procedures performed in each of 1,326 patients Table A1. Demographics characteristics (Patient Specific Variables) Table A2. Tooth specific study variables Table B1. ADA Procedures Codes of anterior Glass Ionomer restorations Table B2. ADA Procedures Codes of posterior glass ionomer restorations Table B3. ADA Procedures Codes amalgam restorations Table B4. ADA Procedures Codes of anterior composite resin restorations Table B5. ADA Procedures Codes of posterior composite resin restorations Table B6. ADA Procedures Codes of metallic INLAY/ONLAY restorations Table B7. ADA Procedures Codes of metallic restorations Table B8. ADA Procedures of porcelain inlay/onlay restorations Table B9. ADA Procedures Codes resin inlay/onlay restorations Table B10. ADA Procedures Codes of crowns-single restorations Table B11. ADA Procedures Codes of Root canal therapy Table B12. ADA Procedures Codes of endodontic procedures Table B13. ADA Procedures Codes of pulpotomy Table B14. ADA Procedures Codes of extractions procedures Table B15. Codes to determine Recall & Prophylaxis visit description Table C1. Clinical Guidelines for Stepwise Excavation Procedure of The University of Iowa College of Dentistry Table D1. Summary table for descriptive statistics for demographic characteristics per patient vii

11 Table D2. Summary table of descriptive statistics for tooth specific variables per patient Table E1. Descriptive statistics for patient age at the time of SWP, the time in months before re-evaluation/re-entry, and the miles travelled to the UICOD Table E2. Frequency distribution of gender for all patients Table E3. Frequency distribution of type of dental insurance at the time of the SWP for all patients Table E4. Frequency distribution for calendar year of treatment at the time of the SWP for all patients Table E5. Frequency distribution for provider level for all patients Table E6. Frequency distribution for tooth type for all patients Table E7. Frequency distribution for tooth arch for all patients Table E8. Frequency distribution for number of surfaces in the treated tooth for all patients Table E9. Frequency distribution for the number of recall examinations and prophy visits in the 18 months prior to the SWP for all patients Table E10. Frequency distribution for the total number of restorations at the UICOD in the 18 months prior to the SWP Table E11. Summary table for frequency distribution of study variables calculated for all patients Table E12. Driving distance to the UI College of Dentistry for the 1,326 study participants Table E13. Single record analysis for patients within the 18 month window Table E14. Descriptive statistics for quantitative covariates for patients that had reentry Table E15. Frequency distribution for gender with and without re-entry Table E16. Frequency distribution of patients that had dental insurance divided by re-entry status Table E17. Frequency distribution of self-pay patients by re-entry status Table E18. Frequency distribution of Medicaid patients by re-entry status Table E19. Frequency distribution of sedative filling restorations for patients that had re-entry viii

12 Table E20. Frequency distribution of glass ionomer restorations for patients that had re-entry Table E21. Frequency distribution of amalgam restorations for patients that had reentry Table E22. Frequency distribution of resin composite restorations for patients that had re-entry Table E23. Frequency distribution of inlays and onlays restorations for patients that had re-entry Table E24. Frequency distribution of crown restorations for patients that had reentry Table E25. Frequency distribution of root canal treatments for patients that had reentry Table E26. Frequency distribution of tooth extraction procedures for patients that had re-entry Table E27. Frequency distribution of implant procedures for patients that had reentry Table E28. Table of re- entry status by gender Table E29. Table of re-entry status by tooth arch Table E30. Table of re-entry status by dental insurance status Table E31. Table of re-entry status by provider level Table E32. Table of Re-entry status by tooth type Table E33. Table of Re-entry status by treatment year Table E34. Table of Re-entry status by number of surfaces Table E35. Table of Re-entry status by total number of recall exams Table E36. Table of Re-entry status by total number of number of miles traveled to UICOD Table E37. Table of Re-entry status by total number restorations per patient Table E38. Descriptive statistics of quantitative variables, comparing subgroups based on re-evaluation/re-entry status at 18 months after performance of stepwise excavation procedure Table E39. Descriptive statistics of quantitative variables, comparing subgroups based on re-evaluation/re-entry status at 18 months after performance of stepwise excavation procedure ix

13 Table E40. Significance probabilities for factors in the final model after adjustment for the other covariates in the model Table E41. Analysis of maximum likelihood estimates associated with the logistic regression coefficients (β s) Table E42. Odds Ratio Estimates Table E43. Results from Multiple Logistic Regression Modeling of Completion of Re-Evaluation/Re-Entry within 18 Months of Stepwise Excavation Procedure Table E44. Provider Level by Insurance Status x

14 LIST OF FIGURES Figure 1. Factors for caries development as described by Fejerskov and Manji Figure 2. Different changes that carious dentin go through in response to caries Figure 3 Bacterial invasion and mineralization phenomena in the dentinal tubules in relationship with hardness...21 Figure 4. Deep Carious lesion...22 Figure 5. Different alternatives for management of deep carious lesions Figure 6. Flow chart for study design Figure 7. Flow diagram detailing data filtering and follow-up for 18 months Figure 8. Distribution of patients that had re-evaluation/re-entry appointment by age group...69 Figure 9. Distribution for miles to UICOD for all patients that had re-evaluation/reentry appointment Figure 10. Distribution of miles for patients that had re-evaluation/re-entry appointment and traveled less than 500 miles...71 Figure 11. Distribution of days until re-entry interval appointment...71 Figure 12. Diagram flowchart of stepwise excavation procedure outcome when considering the first procedure per patient only Figure D1. Distribution of age Figure D2. Distribution of gender Figure D3. Distribution of the number of miles travelled to UICOD Figure D4. Distribution of dental insurance status Figure D5. Distribution of the total number of recalls and prophy exams before the 18 month stepwise excavation procedure was performed Figure D6. Distribution of the total number of restorations per patient18 months before stepwise excavation procedure was performed Figure D7. Distribution of tooth type Figure D8. Distribution of tooth arch Figure D9. Distribution of the number of surfaces treated in first appointment of SWP xi

15 Figure D10. Distribution of the type of provider that performed first appointment SWP Figure E1. Geographic distribution of the reported zip code of reported patient residence Figure E2. Geographic distribution of the reported zip code of reported patient residence within a one-state radius of the UI College of Dentistry Figure E3. Relationship between patient age and driving distance in miles to the UI College of Dentistry Figure E4. Box and whisker plots by Re-entry status Figure E5. Predicted probabilities of re-entry based upon multiple logistic models for selected values of covariates Figure E6. Predicted probability of re-evaluation/re-entry within 18 months of SWP procedure vs. age by tooth type Figure E7. Predicted probability of re-evaluation/re-entry within 18 months of SWP procedure vs. age by provider level xii

16 1 CHAPTER I INTRODUCTION Dental caries disease is a multifactorial, transmissible and infectious dynamic oral disease that results from an imbalance among different factors including oral biofilms, fermentable carbohydrates and tooth surfaces (Sturdevant's 2013, Chapter 2, page 41, Kidd, 2004). This imbalance between tooth and dental biofilm may result in the demineralization of dental hard surfaces by mineral loss caused by plaque acids (Baelum and Ferjerkson, 2003, Kidd 2010). The conventional caries removal approach encourages the removal of all soft carious dentin prior to restoration not only to avoid the caries disease progression and further damage to the dental pulp, but also to provide an adequate marginal seal between the restoration and tooth structure (Kidd 2004). In clinical situations when the carious lesion is deep, the removal of caries represents a high risk of pulp exposure and consequently loss of tooth vitality (Weber et al. 2011). The complete caries removal method has been challenged by strong evidence showing that this treatment of lesions is associated with a much higher incidence of pulpal exposure (Thompson et al., 2010), which subsequently often leads to the need for a root canal or possible tooth extraction. In this context, other alternatives have been reported in the literature to treat deep carious lesions. The preservation of pulp vitality can be achieved with conservative methods of caries removal, such as indirect pulp capping, direct pulp capping, and stepwise excavation. Unfortunately, dentists in general practice do not often use these conservative caries removal approaches. Conservative caries removal techniques, such as the stepwise excavation approach, have the potential to allow the pulp-dentinal complex to repair and initiate reactions in response to bacterial infection (Bjorndal 2008). It is vital that clinicians have complete information about the effectiveness, indications and contraindications of different conservative techniques for the conservative removal of deep carious lesions.

17 2 The stepwise excavation procedure is one of the most common and most conservative procedures to treat deep carious lesions (Oliveira et al 2006). This method of caries excavation is suggested when there is a risk of pulp exposure using the traditional complete caries removal method. The stepwise excavation technique has been studied over thirty years and was first proposed by Magnusson and Sundell (1977) and modified later by Bjorndal et al in It consists of a two-step excavation procedure with the objective of preserving the pulp vitality and avoiding pulp exposure (Chapter 9, page 376, Gopikrishna, 2011). During stepwise excavation only part of the soft and infected carious tissue is removed at the first visit (Kidd 2004) and the cavity preparation is sealed with a temporary restorative material for 6 to 12 months (Maltz et 2013,). At the second visit the restoration is removed and further removal of infected dentin is completed in order to restore the tooth with a final restoration (Kidd 2004). The objective of this is to allow the pulp- dentinal complex to react to the bacterial invasion of dentin by deposition of mineral within dentinal tubules (Massler 1967, Kidd and Fejerskov 2004). This process of mineral deposition is known as tubular sclerosis and it represents a defensive response to the carious process. Another defensive reaction of the dentinal pulp complex is the formation of tertiary dentin (Kidd and Fejerskov 2004) that is deposited at the pulpal end of affected dentinal tubules. The purpose of this two-step procedure is to arrest the carious lesion progression by enhancing these defensive pulp- dentinal complex reactions and allow formation of tertiary dentin prior to final excavation, permitting the dentinal tissue next to the pulp to become thicker and avoid possible pulp exposure (Kidd 2004). A number of studies, including Leksell et al (1996), Magnusson and Sundell (1977), Bjorndal et al (2010), have suggested that stepwise excavation has a higher clinical success rate in terms of tooth survival compared to complete caries removal. Bjorndal et al. (2010) reported that stepwise excavation had a significantly higher rate of

18 3 success (74.1%) compared with complete excavation procedures (62.4%) at 1-year follow-up. Although outcomes based on demographic variables such as age, restorative materials and pulp vitality reports after a follow-up period have been studied in recent stepwise excavation studies (Maltz et al 2012, Maltz et al 2007, Oliveira et al 2006), there is great variety in methodologies, patient populations, operator background and materials used, thus making these studies hard to compare. In view of results showing that stepwise excavation has produced successful outcomes (Leksell et al 1996, Magnusson and Sundell 1977, Bjorndal and Thylstrup 1998, Bjorndal et al 2010) it is important to assess the outcomes of this procedure performed in a US dental school, including its relationship to demographics characteristics. Moreover, using this evidence, dentists can acquire the knowledge to make informed decisions to best treat and restore deep carious lesions. Purpose of the study The purpose of this study was to assess the proportion of patients that had a stepwise excavation procedure re-evaluated at The University of Iowa College of Dentistry, between 2004 and Specifically, the study evaluated the association between different variables and the primary outcome status, defined in terms of whether or not the tooth treated with stepwise excavation procedure was re-evaluated and reentered. Data such as patient age, gender, and number of miles traveled, dental insurance, number of recalls examinations and prophy visits, tooth type, number of surfaces in the treated tooth, type of provider that performed the procedure and tooth arch position were collected and analyzed. Clinical Significance One of the most common conservative procedures to treat deep carious lesions is the stepwise excavation caries removal technique. This procedure is recommended when there is a risk of pulp exposure using the traditional method of full caries removal at a single appointment.

19 4 Several studies have suggested that stepwise excavation is an effective method that conserves the tooth vitality. However, there are no studies reporting the clinical outcomes of completed stepwise procedures in a U.S. dental school which also considered demographics and tooth characteristics. Therefore, it is an important contribution to the dental profession to perform a study to evaluate the relationship between these different variables and whether the procedures were re-evaluated or not. Specifically, this study evaluated the proportion of procedures that were completed and the clinical outcomes of stepwise excavation procedures completed over a 8-year period of time at an academic setting.

20 5 CHAPTER II LITERATURE REVIEW Dental Caries Disease Definition of Dental Caries Disease Dental caries is a transmissible bacterial disease process caused by acids from bacterial metabolism diffusing into enamel and dentin and dissolving the tooth mineral (Featherstone, 2008). Dental caries is also the most prevalent disease in the oral cavity diagnosed and treated by clinicians (Ismail et al., 2007; Fejerskov 2008). This is a very old disease that affected to the human being since people began to develop agriculture. However, the ancient caries pattern was characterized by cervical and root caries and coronal caries wasvery uncommon (Fejerskov and Kidd and 2008). There is evidence that in the nineteenth century as sucrose consumption increased, there was also an increase in the caries severity was observed (Corbett and More, 1976; Fejerskov and Kidd, 2008). Currently, dental caries is one of the most widespread chronic diseases, and patients are at risk for this disease throughout their lifetime (Ismail et al., 2007). Dental caries can be considered on different levels: the tooth surface, the patient and the population. The disease is presented as a dynamic process in the mouth (Featherstone, 2008) which develops through a complex interaction, over time, of components such as the tooth surface, the biofilm and patient s diet (Selwitz et al., 2007). Likewise, caries risk factors also include the person s behavior and education. The term caries can be used to talk about the carious process and the carious lesion (cavitated or non-cavitated) that is associated with that process (Fejerskov 1997; Kidd and Fejerskov, 2004; Selwitz et al., 2007).

21 6 The carious process The carious process is a complex and dynamic process resulting from many cycles of demineralization and remineralization that takes place in the biofilm whose metabolic activity results in the ph in the environment decreasing (Featherstone, 2008). This alteration of the equilibrium between tooth surface and biofilm produces a loss of mineral in the tooth surface, called demineralization, which results in the carious lesion (Kidd, 2004 and 2010). The demineralization process starts when these acids diffuse into the enamel or dentin. This process initiated with the diffusion of calcium and phosphate out of the tooth causing the dissolution of the hydroxyapatite crystals (Featherstone 2004). Thus, the dental carious process is a localized chemical dissolution of a tooth surface resultant from metabolic events (Fejerskov and Kidd and 2008). This process of demineralization occurs in two steps. First, the bacteria metabolize fermentable carbohydrates producing organic acids that diffuse into the tooth through the water amongst the crystals. Bacteria acids reach the enamel crystals and find acid soluble mineral such as calcium and phosphate which are dissolved into the surrounding aqueous areas and start the demineralization process (Featherstone, 2008). If the movement of these calcium, phosphate, and carbonate ions out of the tooth continues, cavitation will result (Featherstone, 2004). The carious process consists of several cycles of demineralization and remineralization in the mouth as long as there are cariogenic bacteria, fermentable carbohydrates and saliva present (Featherstone, 2008). The demineralization process can be reversed in its early stages through fluoride, calcium and phosphate uptake. Calcium and phosphate ions proceeding from the saliva diffuse into the tooth tissue and, assisted by fluoride, can rebuild crystals surface that were affected by the demineralization process (Featherstone, 2008). Then, fluoride ion enhances the remineralization process by facilitating the diffusion of calcium and phosphate into the tooth which allows remineralization of the lesion (Featherstone 1999; 2008). The demineralization or

22 7 remineralization process is determined by the balance between the patient s pathological factors and protective factors Ismail et al., 2007). Pathogenesis of the Dental Caries The pathological factors that are required to produce caries are the presence of acidogenic bacteria, mineralized tooth surface, and fermentable carbohydrates. The primary etiologic factor is the presence of acidogenic bacteria such as Streptoccocus mutans and Lactobacillus, which are recognized as the most important groups contributing to the caries disease (Featherstone 2000, Loesche 1986). These groups of bacteria metabolize carbohydrates producing a variety of acids including lactic, formic, acetic, and propionic (Featherstone 2004). Studies have shown that children are more likely to develop caries if Streptococcus mutans are acquired at an early age. However, this condition might be compensated for other factors such as good oral hygiene and a non-cariogenic diet (Harris et al 2004). Another important pathologic factor of caries is the frequency of ingestion of fermentable carbohydrates. A higher frequency of fermentable carbohydrates consumption is related to higher caries rates. Studies have established the direct relation between sugar consumption and dental caries throughout life (Tougher-Decker and Loveren 2003). In fact, Burt et al., 1988, demonstrated in a three year longitudinal study that a higher average daily consumption and a higher between-meal consumption of sugars are important risk factors for children for proximal caries (Burt 1988). Thus, there are four etiologic factors of dental caries: cariogenic bacteria, fermentable carbohydrates, susceptible tooth and time. On the other hand, there are protective factors that inhibit the carious process and help prevent the disease. These include high salivary flow, numerous salivary components, such as antimicrobial proteins, fluoride from extrinsic sources, and certain dietary components that have an anti-cariogenic effect (Featherstone 2004). Saliva has a protective role in counteracting demineralization by its buffering and re-mineralization

23 8 capacity, replacing calcium and phosphate in the tooth surface that has been removed by the demineralization process (Ten Cate 1991, Featherstone 2000). Thus a decrease in salivary flow exacerbates the effects of demineralization and the carious process. If an imbalance between pathologic and protective caries factors occurs with pathological factors predominating, the demineralization process leads to caries and cavitation as a final outcome (Featherstone 2000). Caries Risk factors for a patient are multifactorial and can vary over time. Insufficient salivary flow or alteration in saliva composition, high bacteria counts and insufficient fluoride exposures are considered risk factors for caries. The carious process is also associated with behavioral risk factors including poor oral hygiene and dietary habits, such as frequent sugared snacks between meals. Caries risk is also related to a person s lifestyle, health and medications (Featherstone 2004). The diagram (Figure 1) depicted below shows that personal and oral environmental factors contribute to the caries development process.

24 9 Figure 1. Factors for caries development as described by Fejerskov and Manji (Adapted from Fejerskov and Manji 1990 and from Selwitz et al outcome (Featherstone 2004). Dental caries is a dynamic process, which in its early stages is reversible and even in its more advanced stages can be arrested (Zero, 1999). Although early detection and intervention could prevent the progression of lesions, the diagnosis of caries remains a challenge (Ahmad, 2010, chapter 6, page 21). Caries diagnosis and interventions have developed through the years. Currently, clinicians use visual, tactile, and radiographic caries detection techniques to detect dentinal and enamel changes (Zero, 1999). For many years the treatment of dental caries was focused on the treatment of the consequences of the caries rather than treating the caries disease itself. Dentistry traditionally treated caries with surgical removal of lesions followed by the restoration of

25 10 tooth structure rather than using a diagnostic and preventive approach towards the disease of caries. Classification of Dental Caries Disease Dental caries is classified by location as smooth-surface caries, pit and fissure caries, enamel caries, dentinal caries, secondary caries, early childhood caries, and root caries by clinicians and researchers (Featherstone 2004). There are other classifications that describe the carious process clinically or histologically. The International Caries Detection and Assessment System (ICDAS) measures the carious process at different stages by using defined criteria for clinical visual caries detection (Ismail et al 2007). The World Health Organization (WHO) criteria uses an index to measure the tooth surfaces that are sound, decayed, filled or indicated for extraction (WHO, 1997). Clinical dental caries classification: Classification based on location 1. Smooth surface caries: lesions existing on smooth surfaces of teeth. Tooth surfaces included: buccal, lingual, mesial and distal surfaces. 2. Pit and fissure caries: lesions existing in a pit or fissure area. 3. Occlusal caries: carious lesions on occlusal surfaces of teeth. 4. Proximal caries: lesions on a proximal surface of teeth. 5. Enamel caries: lesion in dental enamel, which indicates that the lesion has not penetrated into dentin (Art and Science of operative Dentistry 6 th ed, 2013). 6. Dentin caries: lesion into dentin 7. Coronal caries: carious lesion that exists on any surface of the anatomic tooth crown (Art and Science of operative Dentistry 6 th ed, 2013). 8. Root caries: carious lesion on the root surface of teeth (Art and Science of operative Dentistry 6 th ed, 2013).

26 11 9. Primary caries: A carious lesion not adjacent to an existing restoration or crown (Art and Science of operative Dentistry 6 th ed, 2013). 10. Secondary caries: A carious lesion adjacent to an existing restoration, crown, or sealant. Recently the term caries adjacent to restoration and sealants (CARS) has been used (Art and Science of Operative Dentistry 6 th ed, 2013). This term is also referred to as recurrent caries that implies a primary carious lesion, which was restored, but reoccurred (Art and Science of operative Dentistry 6 th ed, 2013) 11. Residual caries: indicates a carious lesion that was not completely removed before placing a restoration (Art and Science of operative Dentistry 6 th ed, 2013). Classification based on cavitation status: 12. Cavitated carious lesion: carious lesion that results in the breaking down of tooth tissue. 13. Non-cavitated carious lesion: carious lesion that is not cavitated or has no break down the enamel tooth structure. Classification based on activity status: 1. Active carious lesion: lesion that is considered to be in ongoing mineral loss or demineralization due to metabolic activity in the biofilm (Kidd and Fejerskov 2004). 2. Inactive carious lesion: lesion that does not require professional intervention because it is considered to be biologically inactive at the time of examination. It is unlikely to progress and result at mineral loss due to metabolic activity in the biofilm (Kidd and Fejerskov 2004). 3. Rampant Caries: term that describes extensive, active and multiple carious lesions in the same person (Art and Science of operative Dentistry 6 th ed, 2013, page 43).

27 12 Classification based on caries experience the World Organization system The WHO uses an index which is applied to the permanent dentition and is expressed as the total number of teeth or surfaces that are decayed (D), missing (M), or filled (F) in an individual (WHO 1997). The Decayed, Missing, Filled (DMF) index has been used for more than 70 years and is well established as the key measure of caries experience in dental epidemiology (World Health Organization, Oral Health 1997). When this index is applied to teeth specifically, it is called the DMFT index, and scores per patient can range from 0 to 28 or 32, depending on whether the third molars are included in the scoring (World Health Organization Oral Health 1997). When the index is applied only to tooth surfaces (five per posterior tooth and four per anterior tooth), it is called the DMFS index, and scores per patient can range from 0 to 128 or 148, depending on whether the third molars are included in the scoring (World Health Organization, Oral Health 1997). Classification based on severity or depth ICDAS system The International Caries Detection and Assessment System (ICDAS) (Ismail et. al., 2007) is summarized in table 1. Classification based on radiographic evaluation In clinical practice, visual- tactile caries examination is frequently complemented by radiographies. Table 2 presents the radiographic classification of caries proposed by Ekstrand et al. (1997).

28 13 Table 1. Diagnostic levels of dental caries measured using the International Caries Detection and Assessment System (ICDAS) (Ismail et al 2007). (Adapted from Ismail et al 2007, Community Dent Oral Epidemiol 2008; 36: 55 68). Code Description 0 Sound tooth surfaces There should be no evidence of caries (either no or questionable change in enamel translucency after air-drying for 5 s). 1 First visual change in enamel When seen wet there is no evidence of any change in color attributable to carious activity, but after air drying for 5 s a carious opacity is visible that is not consistent with the clinical appearance of sound enamel. 2 Distinct visual change in enamel When viewed wet there is a carious opacity or discoloration that is not consistent with the clinical appearance of sound enamel When viewed from the occlusal direction, this opacity or discoloration may be seen as a shadow confined to enamel. 3 Initial breakdown in enamel due to caries with no visible dentin Once dried for 5 s there is distinct loss of enamel integrity, viewed from the buccal or lingual direction. These lesions may also have a discolored dentin shadow beneath the marginal ridge 4 Noncavitated surface with underlying dark shadow from dentin This lesion appears as a shadow of discolored dentin visible through an apparently intact marginal ridge, buccal, or lingual walls of enamel. The darkened area is an intrinsic shadow which may appear as grey, blue, or brown in color 5 Distinct cavity with visible dentin Cavitation in opaque or discolored enamel with exposed dentin in the examiner's judgment 6 Extensive distinct cavity with visible dentin Obvious loss of tooth structure, the extensive cavity may be deep or wide and dentin is clearly visible on both the walls and at the base. An extensive cavity involves at least half of a tooth surface and possibly reaching the pulp

29 14 Table 2. Radiographic classification of caries. (Adapted from Ekstrand et al., 1997). Criteria Score No visible radiolucency. 0 Radiolucency in the enamel. 1 Radiolucency in the dentin, involving the surface or outer third of the dentin. 2 Radiolucency in the dentin, involving the middle third of the dentin. 3 Radiolucency in the dentin, involving the inner third of the dentin. 4 Classification based on chronology Early childhood caries (ECC) Early childhood caries is defined as the presence of 1 or more carious lesions (non-cavitated or cavitated lesions), missing teeth (due to caries) or filled tooth surfaces in any primary tooth in a child 71 months of age or younger (American Academy of Pediatric Dentistry 2008). Some pre-disposing factors are the early colonization of mutans streptococci, the use of a feeding bottle containing sugary solutions and night breast-feeding (Davies 1998). ECC involves the maxillary primary incisors within months after their eruption and spreads rapidly to involve other primary teeth (Davies 1980). ECC is most often seen in children with unusual dietary history such as addition of syrup, honey or sucrose to the formula or the use of a pacifier dipped in honey or other sweeteners. The stagnation of milk at the cervical of anterior teeth and the fermentation of disaccharide lactose contribute to the carious process (Davies 1998). Histo-Pathology of Dental Caries: Enamel changes during caries progression Enamel changes caused by the caries progression can be visualized through polarized light microscopy and scanning electron microscopy. Studies have described the ultra-structural changes in the enamel due to demineralization caused by the biofilm using scanning electron microscopy (Holmen et

30 15 al., 1985 and 1987). These series of experiments showed that after one week of caries progression, not changes were detected clinically. However at the ultra-structural level there were micro porosities and signs of direct dissolution of the outer enamel surface (Kidd and Fejerskov 2004). After two weeks of continuous biofilm activity, enamel changes were clinically detected and those changes were recognized as white spot lesion. After 3 and 4 weeks the lesion could be detected before tooth surfaces were airdried. This lesion was ultra-structurally described as a continued enlargement of inter crystalline spaces because of the complete dissolution of the crystal peripheries (Kidd and Fejerskov 2004). These ultra-structural changes give the lesion the opaque and matte surface appearance when enamel samples were air-dried. Polarized light microscopy (PLM) The classical histology describes four distinct zones within the enamel carious lesion that can be visualized using transmitted and polarized light microscopy: the surface zone, the body of the lesion, the dark zone and the translucent zone. The surface zone is the outermost zone of enamel caries which is an intact surface layer with a typical thickness of um, relatively high mineral content and a larger crystal size than sound enamel (Meyer-Lueckel and Paris, 2013). The body of the lesion is below surface zone and presents the highest degree if demineralization. The crystals in this zone may be partly or completely dissolved along and within the prisms. Beneath the body of the lesion, the dark zone surrounds the body of lesion zone and looks like as a dark-brownish area when visualized using polarized light microscopy (Meyer-Lueckel and Paris, 2013). The dark color of this zone indicates that has smaller porosities than the size of quinolone molecules which is used as an index matching fluid in PLM. The translucent zone is the innermost area of the caries enamel lesion which presents larger porosities than the size of quinolone molecules. These zones have been identified on the basis of differences in

31 16 the amount and size of porosities using transmitted and polarized light microscopy (Meyer-Lueckel and Paris, 2013). Scaning electron Microscopy (SEM) SEM technique of the enamel surface allows visualizing the early stages of caries demineralization. The different demineralization types at the prism level have been described as sound enamel ; etched enamel, surface softened enamel and carious enamel. Under a layer of dental plaque, it is possible to observe etched enamel which shows a thin layer removed and the surface is rough. Every carious process in enamel shows a slight etching of the surface (Meyer-Lueckel and Paris, 2013). On the surface of softened enamel, the acid attack has removed the inter-prismatic areas in the initial state of carious lesion and finally subsurface or carious enamel that has low mineral content (Thylstrup et al., 1994; Featherstone, 1980). Carious lesion progression in dentin As soon as the enamel lesion reaches the dentino-enamel junction (DEJ), the process of dentin demineralization can begin (Bjorndal, Darvan and Thylstrup 1998). The first histologic change in the dentin beneath an enamel lesion is the formation of hyper-mineralized dentinal tubules. When bacterial acids invade the dentin, crystals are deposited within and along the walls of the dentinal tubules. This reaction of the pulpdentinal complex is known as tubular sclerosis (Fejerskov, 2008). Some of these deposited crystals are called rhombohedral or whitlockite crystals (Fejerskov 2008). These changes result from the different ph gradient caused by dissolution or reprecipitation of dentin mineral which produces hyper mineralized dentinal tubules (Fejerskov 2008). According to some studies, tubular sclerosis is the first reaction to caries in the pulpo-dentinal complex and this reaction can be observed in the dentin before any signs of demineralization (Fejerskov and Kidd 2008; Bjorndal 2008).

32 17 Tertiary dentin formation Along with the tubular sclerosis process, tertiary dentin occurs within the pulp chamber (Fejerskov, 2008). Tertiary dentin is described as a type of irregular dentin structure deposited on the pulpal aspects of primary or secondary dentin, resulting from areas of external irritation (Klinge, 2001). Tertiary dentin is deposited in specific sites in reaction to injury by damaged odontoblasts or replacements of cells from the pulp. There are different patterns of tertiary dentin since the amount of deposition depends on the degree of injury, the more severe the injury, the more rapidly the amount of tertiary dentin deposition (Nancy, 2007). The tertiary dentin and tubular sclerosis processes represent the defensive reaction mechanism of the tooth to the carious process. Zones of Dentin Caries: 1. Infected Dentin: the infected dentin is described as the outer most carious layer and is characterized by bacteria filling the tubules and granular material in the intertubular space (Figure 2). This is the layer that the clinician will find first when removing a carious lesion. As the infected dentin has higher amounts of bacteria than inner dentin layer, it is damaged to the magnitude that it cannot be remineralized (Ngo et al., 2006). Widening and distortion of the dentinal tubules also characterize this zone. Additionally, the collagen in the infected dentin is irreversibly denatured (Art and Science of operative Dentistry 6 th ed, 2013). Massler et al., (1967) and Fusayama (1991) suggested that only the outer infected layer should be removed during cavity preparation. The reason to remove this layer is to allow a long-term restoration and to prevent the spread the infection (Art and Science of operative Dentistry 6 th ed, 2013). 2. Affected Dentin: This layer is also defined as the inner layer. The affected dentin is characterized by partial demineralization (Ngo et al., 2006) and initial

33 18 formation of fine crystals in the tubule lumen at the advancing bacteria front. The affected dentin is softer than normal dentin and shows loss of mineral from intertubular dentin and many large crystals in the lumen of the dentinal tubules (Figure 2, Art and Science of operative Dentistry 6 th ed, 2013). The affected dentin can be classified in three sub-zones: turbid, transparent and substransparent dentin (Marshall et al., 2001) as shown in Figure 2. The turbid zone is characterized by absence of bacteria in the tubules and by loss of mineral in the inter-tubular and peri-tubular dentin. Following this zone, the transparent dentin presents crystals in the lumen of the tubule making the zone appears transparent when observed in SEM (Meyer-Lueckel and Paris, 2013). According to studies (Fusayama, 1993) there is unaltered dentin layer below the subtransparent layer. There are studies that have shown that the collagen cross-linking of this layer remains intact (Mount 2004, Ngo et al 2006). It has also been shown that the affected layer can be remineralized (Massler et al., 1967, Fusayama et al., 1966, 1991, Ngo et al., 2006). Therefore, it is suggested that the affected dentin layer should be preserved during the caries removal procedure and treated with a biocompatible material as calcium hydroxide, glass ionomer or a similar material (Ngo et al 2006). 3. Normal Dentin: It is the deepest dentin area in a carious lesion. This layer presents tubules with odontoblastic processes, which are smooth and with no crystals in its lumens. There are no bacteria present in the tubules of this layer. The intertubular dentin has normal cross-banded collagen and normal dense apatite crystals (Art and Science of operative Dentistry 6 th ed, 2013). Initial Pulp-dentinal complex reactions to caries The etiology of pulp inflammation under caries is due to the presence of bacteria. It has been acknowledged for decades that the pulp can be inflamed under lesions

34 19 confined to enamel, as well as in relation to deep dentin caries. Conventionally, the clinical focus of caries and pulp reaction has been on late stages of lesion progression. Usually, the main focus of carious lesion has been related to when and how the pulp tissue should be treated or removed (Bjorndal 2008). Studies have demonstrated that when bacteria acids infiltrate into the enamel in well-defined enamel lesions, morphologic changes in odontoblasts are observed (Bjorndal, Darvan and Thylstrup 1998). Also, can molecular changes in the odontoblast cells leading to the production of extra-dentinal matrix occurrs. Even before alterations in the dentin have occurred, the dentin and pulp present reactions including a decrease of the odontoblast -predentin region (Fejerskov 2008). The most important change is the size of the odontoblast cells which decrease in size compared to unaffected odontoblasts of similar location and age (Fejerskov 2008). In addition, the sub-odontoblastic region is less pronounced, as pulpal cells have proliferated into the cell-free zone. The pulpal response taking place subjacent to enamel lesions with different lesion activity also reveals different cellular reaction patterns in the subodontoblastic region (Bjorndal 2001). Dentin hypermineralization occurs with cellular alterations along the odontoblast predentin region as the demineralized enamel approaches the amelo-dentinal junction (Bjorndal 2001). This dentin hypermineralization might be compared with a localized and accelerating process of dentinal sclerosis normally occurring as a biological aging phenomenon (Fejerskov 2008). While the carious process continues to advance, the defense mechanism of tubular sclerosis will progress (Figure 3). At this point, the individual bacteria are still far too large to penetrate the demineralized rod and inter-rod enamel. However, when the enamel layer is disintegrated, bacterial invasion of the demineralized dentin and enamel occurs. When the exposure of dentin occurs, the superficial layer of dentin will be decomposed through bacteria acid attack. This zone is called the zone of destruction or infected dentin (Fejerskov, 2008). In this zone can be

35 20 seen invasion of bacteria and results in irreversible damage that can never remineralize (Fusayama, 1988). And the deepest dentin carious layer, the affected dentin, has been described as being harder as result of remineralization (Figure 3). As was discussed before, tubular sclerosis process is produced by odontoblastic processes in the affected dentin layer (Figure 3). This reaction of the pulp- dentinal complex, tubular sclerosis, is an additional mechanism distinct from tertiary dentin formation (Fejerskov, 2008). Figure 2. Different changes that carious dentin go through in response to caries. Zone (1) corresponds to normal dentin; zone (2) to affected dentin with 3 subzones: subtransparent, transparent and turbid; and zone (3) corresponds to infected dentin. (Adapted from Sturtevant's Art and Science of Operative Dentistry, Page 61, Chapter 2, 6th Edition)

36 Figure 3 Bacterial invasion and mineralization phenomena in the dentinal tubules in relationship with hardness, figure adapted from Ogawa et al.,1983 (Fejerskov and Kidd, Dental caries: the disease and its clinical management, page 44, 2008). 21

37 22 Deep carious lesions Deep carious lesion definition A deep carious lesion has been defined as a lesion where its penetration depth is in the range of three fourths of the entire thickness of the dentin or more when evaluated on a radiograph (Bjorndal, 2008). In addition, removal of this type of carious lesion has potential risks to expose the pulp; therefore, the selection of an appropriate treatment is crucial to avoid loss of tooth vitality. Figure 4. Deep Carious lesion The treatment of deep carious lesions (Figure 4) has been difficult to manage for many years due to the risk of pulp exposure (Kidd, 2004, Bjorndal, 2008). The complete caries and discoloration removal has been demonstrated to be risky in treating these kinds of lesions because the likelihood of exposure of the pulp is high, which would mean the patient would need a root canal or tooth extraction. Exposing the pulp can lead to more invasive treatments with adverse economic and physiologic consequences for the patient.

38 23 Dentists should follow a conservative strategy of trying to avoid a pulp exposure. The preservation of pulp vitality can be achieved with conservative methods of caries removal (Maltz et al., 2010). Conservative caries removal methods such as indirect pulp capping, direct pulp capping, partial caries removal and stepwise excavation have been proposed in the literature (Weber et al., 2011). Unfortunately, even though conservative removal approaches have existed for a long time, they are not often used by dentists in general practice (Weber et al., 2011). A deep carious lesion implicates a high potential of pulp exposure as stated by Bjorndal, (2008). In 1998, Bjorndal and Thylstrup did a practice-based observational study where they asked a group of general dentists to evaluate the penetration depth of carious lesions that would cause a pulpal exposure. The authors reported that most dentists selected lesions that penetrated within three fourths of the entire dentin thickness or more as evaluated on radiographs. These findings showed that the deep cariouss lesion definition differs significantly among dentists (Bjorndal, 2008). Deep carious lesion classification based on severity: Years ago, Massler and Fusayama proposed that there are principally two layers in carious dentin; the outer layer, which is heavily infected with microorganisms and the inner layer, which is immediately adjacent to sound dentin on the floor of the carious lesion (Ngo et al., 2006). These same authors (Massler et al 1967 and Fusayama et al 1966) identified the inner layer as the affected layer and they determined that this layer can be remineralized. More recently, the caries progression in dentin has been described in three zones: turbid, transparent and subs-transparent dentin (Art and Science of operative Dentistry 6 th ed, 2013).

39 24 Closed and open cariogenic ecosystems: Closed ecosystem Proximal and occlusal dentinal lesions usually begin as a closed ecosystem. For example, carious lesion in the occlusal surface starts as a closed ecosystem, but if left untreated the white and weakened enamel will break due to mechanical stress, so this lesion develops into an open ecosystem. (Bjorndal 2002) Open ecosystem Open cariogenic ecosystems are typically developed in smooth non- proximal surfaces. A very homogenous microflora is apparent in the deep closed lesion environment containing several different subspecies of lactobacilli, whereas a much more heterogeneous microflora can be detected as the dentin exposure increases and becomes more open with various signs of proximal surface destruction (Bjorndal 2002). Deep dentin carious lesion classification based on activity: The progression of carious lesions into the dentin may be slow or rapid depending on lesion activity and dentin permeability. This is related to the status of the cavity. For instance, in a closed lesion environment the lesion will rapidly progress compared to an open lesion ecosystem in which the lesion progresses more slowly (Bjorndal, 2008). Slowly progressing lesions Slowly progressing lesions are characterized by generating tubular dentin formation. The tertiary dentin shows a mixture of reactionary dentinogenesis and dentin produced by new odontoblast-like cells. Slowly progressing lesions or arrested lesions have a darker, brownish discoloration and less pronounced softening of the dentin (Bjorndal 2008).

40 25 Rapidly progressing lesions: Rapidly progressing lesions characteristically produce odontoblast necrosis followed by formation of atubular dentin also known as fibrodentin. (Bjorndal 2008). In the presence of a rapid lesion progression, the odontoblastic processes are destroyed without having produced tubular sclerosis. Those are called dead tracts in the dentin. These empty tubules are invaded by bacteria that produce liquefaction tissue. This has been called the bacterial penetration zone. (Kidd and Fejerskov 2004). Many articles have shown that the color and consistency of demineralized dentin in active progressing lesions is yellowish to light brown and is decreased in hardness in comparison to unaffected dentin, while arrested lesions are darker and possess a less pronounced softening of the dentin (Bjorndal 1998 and Thylstrup 1998, Bjorndal 2008, 2001, Bjorndal and Larsen 2000).In short, the demineralization process will take place in dentin and the reactionary dentin will be less organized and less mineralized (Bjorndal, 2001). To summarize, in rapidly progressing lesions no protective changes in the dentin occurs and the odontoblast may be irreversibly affected. Likewise, while the carious process continues to advance, the defense mechanism of tubular sclerosis will progress. After the dentin demineralization is originated, the cariogenic nature of the biofilm shows ph gradients which cause dissolution of the dentin mineral. (Fejerskov,2008). In actively progressing lesions the demineralization process will take place in dentin and the reactionary dentin will be less organized and mineralized (Bjorndal, 2001). In addition, dentin carious lesions cause pulp reactions that produce different patterns of tertiary dentin. Thus, the tertiary dentin formation can vary relative to the evolution of each lesion (Bjorndal and Mjor 2001; Kidd 2004). For instance, in slowly progressing lesions, besides the increased mineralization of the peritubular dentin, there is formation of reactionary dentin that is a type of irregular dentin that forms at the pulpal end of the affected tubules in a very active lesion.

41 26 In rapidly progressing lesions, a different pattern of tertiary dentin is observed where the destruction of the odontoblast and formation the odontoblast- like cells are differentiated from the pulp to form reparative dentin. Reactionary dentin is frequently the result of moderate stimuli, while reparative dentin is produced by a stronger stimuli and has a more irregular structure formed by odontblast-like cells (Klinge 2001). Complete caries removal technique: Definition of complete caries removal technique The conventional practice in caries removal consists of removing all softened and infected dentin until hard dentin is obtained: that is, complete caries removal. Some studies have explored different techniques for conventional caries removal such as carbon steel bur, cariole gel, soon-abrasion, air-abrasion, and hand excavation (conventional method). In their study Banerjee et al., (2000), evaluated the efficiency and the effectiveness of carious dentin removal using four different chemo-mechanical methods of excavation compared to hand excavation. The authors in this study concluded that conventional hand excavation showed the best combination of efficiency and effectiveness for caries removal within the parameters of their study. Traditionally, the surgical approach of caries has involved the removal of all carious tooth structure; however, the concept of the complete caries tissue removal has changed during the last decades. This is because there are a number of consequences associated with complete caries removal technique, such as having pulp exposure and decreased remaining dentin thickness (Rickets et al., 2013). Table 3 presents some of the advantages and disadvantages of complete caries removal technique. The introduction of the concept of minimally invasive dentistry (MID) has transformed the traditional surgical management of caries (Rickets et al., 2013) into a more conservative one. These conservative caries removal techniques are becoming more

42 27 commonly accepted as they have aimed to reduce the adverse consequences of restorative treatment (Rickets et al., 2013). Table 3. Complete caries removal technique advantages and disadvantages. Advantage: Complete elimination of deep carious lesion One visit Disadvantages: High risk of pulpal exposure Extensive removal of tooth structure Pulp exposure risk secondary to treating deep carious lesions The conventional approach or complete caries removal technique is more challenging with deep carious lesions as it is likely that the pulp will be exposed. Several treatment approaches have been proposed to solve the problem of treating deep carious lesions such as indirect pulp capping and stepwise exaction technique (Bjorndal, 2008). One approach, it is to arrest the carious lesion progression by applying a protective agent to the pulpal floor, such as calcium hydroxide (CaOH) or zinc oxide eugenol and subsequently to restore the tooth. This technique is known as indirect pulp capping (Murray and Peter 2002; Kidd 2004). Studies have shown that CaOH has good properties of for the treatment of deep carious lesions. For instance, Leung et al., (1980) provided evidence that CaOH used as a liner over demineralized dentin significantly decreases the number of remaining bacteria. Mickenautsch et al., (2010) did a systematic review of 6 randomized and non-randomized clinical trials and concluded that there were no differences between resin-modified glass ionomer cement and Ca-OH regarding to the pulp response when placed in deep cavities. However, studies have revealed that placing calcium hydroxide over deep carious lesions might stimulate irreversible pulpal

43 28 degeneration (Falster et al 2002). Likewise, the calcium hydroxide material has unstable physical properties that allow material particles to migrate into pulp tissue, then causing inflammation, which may develop into necrosis (Walton and Langeland, 1978, Murray et al., 2002). There is evidence that new generations of calcium-hydroxide-containing materials have improved physical properties, but they are still not insoluble, and they eventually allowed bacterial leakage to occur (Murray et al., 2002). Therefore, the most commonly used criterion to remove deep caries includes removing all affected and infected (softened dentin) with spoons and burs. Additionally, some schools still teach that all stain should be removed from the dentin; however, some authors advocate leaving affected dentin that is hard and leathery as a more conservative approach (Kidd et al 1996, 2004). Improved understanding of deep carious lesion The conventional approach assumes that biofilm and microorganisms contained within the infected dentin drive the carious process (Kidd et al., 2010). Therefore, the goal of conventional operative procedures is to eliminate all the carious softened dentin using a bur and excavator in order to arrest the lesion (Chapter 9, page 374, Gopikrishna, 2011). Many years ago G.V Black (1908) stated, It is better to expose the pulp of a tooth than to leave it covered only with softened dentin. This belief has dominated dental education for many years (Kidd et al 1996). Today, there is important evidence that infected dentin is different from soft and affected dentin in the carious process. Fusayama in 1988 reported in his study that the infected superficial layer of dentin would never remineralize but the deepest layer (affected dentin) was hard due to the remineralization process. Almost seven years later, Kidd et al., 1995, reported that under old restorations dry dentin was found, which could be residual caries in the cavity preparation. This deepest layer, affected dentin, was also proven not to be bacterially compromised ( Kidd et al.,1995).

44 29 Therefore, the question is what scientific evidence is there to support the need for removal of the affected dentin. Several stepwise excavation studies have been conducted which provide important evidence as to the effect of not eliminating all infected dentin, but rather providing a complete sealing of the cavity (Kidd 2004). Incomplete Caries Removal Approaches to treat deep carious lesions: Different approaches to treat deep carious lesions have been advocated for preventing exposure and damage to the pulp. The following procedures are most commonly known: Indirect pulp treatment (IPT): Indirect pulp treatment is a one-step incomplete removal approach. This technique consists of removing the carious dentin to within approximately 1 mm of the pulp and leaving a thin layer of caries at the deepest sites of the cavity preparation above the pulp (Schwendicke et al., 2013; Falster et al 2002). This thin carious layer left above the pulp is called residual carious dentin (Kidd 2004; Leung et al., 1980). The main objective of this approach is to avoid a pulp tissue exposure where complete caries removal would result in pulp exposure with subsequent loss of tooth vitality (Orhan et al., 2010). This procedure also consists of the dentin tissue close to pulp being covered with an agent to protect the pulp from additional injury and to promote healing and repair via formation of secondary dentin (Fejerskov 2008). In IPT there are no exact methods to determine how much carious tissue must be removed (Orhan et al., 2010). Several studies have reported the success of this technique in primary teeth (Marchi et al 2007, Farooq et al 2000). Therefore, IPT is indicated as the most appropriate treatment for primary teeth with deep caries diagnose in absence of irreversible pulpitis symptoms. However, further research should be conducted to report the success of indirect pulp capping in permanent teeth. It

45 30 has also been described that this procedure has been applied in permanent teeth (Bjorndal 2008). Stepwise excavation This method is a two-step incomplete caries removal approach and will be described in detail in the next section. In this procedure the carious dentin tissue is incompletely removed at the first step. After a period of 6 to 12 months the cavity is reopened and further removal of infected dentin is completed in order to definitively restore the tooth. In this approach there are relatively greater amounts of carious dentin left behind during the first excavation or first step (Bjorndal 2008b). Moreover, the final excavation is performed on carious dentin that usually shows the classical clinical signs of arrested caries, being more brownish and of a harder consistency. The final excavation is easier as the dentin is harder and darker, so it is more controllable than soft demineralized dentin. The effectiveness of the stepwise excavation procedure for the management of deep carious lesions has been documented with long-term recalls showing arrested caries (Bjorndal et al 2000 and Bjorndal 2008). Case selection consists primarily of deep lesions considered likely to result in pulp exposure if treated in one visit by complete excavation. The dentinal lesion typically involves more than 75% of the entire dentin thickness as evaluated by radiographs (Bjorndal 2008). Difference between indirect pulp capping and stepwise excavation procedure The main difference is that the indirect pulp-capping procedure almost completely removes the affected dentin, leaving a thin layer of residual demineralized dentin and reentry is not made. Thus IPT is a one-step procedure while the stepwise excavation involves re-entry at varying intervals (Fejerskov 2008).

46 31 Partial Caries Removal This caries removal approach is one-step incomplete caries removal that omits the re-entry step since the residual affected dentin tissue is sealed under the definitive restoration in a first and only visit (Schwendicke et al., 2013). In this procedure, the dentist removes part of the dentinal caries and seals the tooth permanently (Ricketts et al., 2013). However, partial caries removal definition differs considerably into the literature. Partial caries removal definition goes from simply beveling enamel at the entrance to the cavity to perform peripheral caries removal and leaving soft infected carious dentin pulpal; to removal of caries until firm, stained dentin is reached and then placement of an permanent restorative material (Ricketts, 2008). In short partial caries removal includes the removal of variable amounts of superficial caries and seal of remaining caries permanently (Innes et al., 2011). The objective of partial removal approach is to remove only superficial carious dentin that is highly infected, and preserve the dentin able to remineralize. The result is to decrease the overall bacterial load and arrest lesion progression (Kidd 2004; Lula et al 2009, Lula et al., 2011). Ultraconservative approach The ultraconservative caries technique consists in removing minimal caries at the entrance to a cavity, sealing the remaining caries and placing a permanent filling (Ricketts et al., 2006). This method has been also recently been called no dentinal caries removal in the literature (Ricketts et al., 2013). There are some studies where the amount of carious tissue was minimal, removing just enamel and with no dentinal caries removal (Mertz-Fairhurst et al., 1998). In this study, Mertz-Fairhurst et al., 1998, the authors selected teeth with clinical and radiographic evidence of occlusal caries and no attempt to remove any carious dentin. These teeth were restored with acid etched composites and covered with fissure sealant, and then these 156 ultraconservative sealed restorations were followed up for ten years. The authors concluded that the bonded and

47 32 sealed composite restorations placed over the frank cavitated lesions arrested the clinical progress of these lesions for 10 years (Mertz-Fairhurst et al., 1998). Figure 5 shows different alternatives or approaches to treat deep carious lesions. Figure 5. Different alternatives for management of deep carious lesions. Stepwise excavation approach literature and background Stepwise excavation technique definition The stepwise method is a two-step incomplete caries removal approach where the carious dentin tissue is incompletely removed at the first step and carious dentin is left in proximity to the pulp under a temporary filling (Schwendicke et al., 2013). In the stepwise caries removal technique, only part or all the soft and infected carious tissue is removed at the first visit during the acute phase. In the second step (second visit) 6 to 12 months later, a re-entry caries removal procedure is accomplished, complete removal of all carious tissue is performed and a definitive restoration is placed (Schwendicke et al.,

48 ). The purpose of this procedure is to arrest the carious lesion progression in order to allow the formation of tertiary dentin before final excavation, which makes the dentin tissue next to the pulp thicker and the pulp exposure less likely (Kidd 2004). The stepwise excavation technique has been studied over thirty years and consists of a two-step excavation procedure with the objective of preserving the pulp vitality and avoiding pulp exposure (Fejerskov and Kidd 2008). This method was first proposed by Magnusson and Sundell (1977) and modified later by Bjorndal et al in Stepwise excavation technique purpose The purpose of the stepwise excavation technique is to preserve pulp vitality; stimulate re-mineralization and tubule sclerosis preserving affected dentin (Bjorndal et al 1997, Bjorndal 2008, Maltz and Garcia 2012). Stepwise excavation technique description Stepwise excavation technique consists of an initial excavation in which the necrotic and disorganized tissue is removed, leaving soft tissue over the pulp wall (Bjorndal 1998, Maltz and Garcia 2012). The cavity is then restored and well-sealed with a provisional restorative material allowing the pulpal-dentinal complex to react by placing sclerotic dentin in dentinal tubules and producing tertiary dentin (Bjorndal 2000, Bjørndal, 2008). When the cavity is consequently re-entered, the remaining carious dentin tissue must be removed (Maltz and Garcia 2012). Many studies have shown that the stepwise excavation caries removal technique produces less pulp exposure compared with the complete caries removal technique (Magnusson and Sundell, 1977; Leksell et al., 1996; Ricketts et al., 2006, Maltz and Garcia 2012, Bjørndal and Thylstrup, 1998, Bjørndal et al., 2010).

49 34 Stepwise excavation studies and randomized clinical trials The method of stepwise excavation caries removal has been demonstrated to be a successful method in preserving the vitality of tooth pulp (Magnusson and Sundell 1977, Bjorndal et al 1997, Bjorndal and Thylstrup 1998, Bjorndal and Larsen 2000). There have been several clinical trials, which have achieved high success rates (74.1% to 88%) with this technique (Leksell et al, 1996, Bjorndal et al 1997, Bjørndal and Thylstrup, 1998; Bjørndal et al. 2010). For this reason the stepwise excavation procedure has been used for decades as a caries removal technique with high success in European countries (Magnusson et al, 1977). As a pioneer in the research on stepwise caries removal, Bjorndal considers maintaining pulp vitality as an important objective for clinicians in prevention and preservation of tooth structure. Stepwise excavation minimizes the risk of pulpal exposure during the first excavation and promotes physiological reactions of healing from the pulp-dentin organ (Bjorndal et al 1997). In Bjorndal s study with Thylstrup in 1998, they performed a 1 year follow-up study, where 24 dentists performed stepwise excavation treatments on permanent teeth with deep carious lesions. The authors performed clinical recordings on these teeth with the objective of monitoring clinical changes in the dentin during the treatment. The clinicians also made follow up observations at specified intervals by recording symptoms and repeated radiographic evaluations for a period of 2 years. The sample consisted of 94 teeth with deep carious lesions that, based on the clinician s assessment, if treated by conventional caries removal would have resulted in pulp exposure. Pretreatment radiographs were used to estimate lesion size, and electric pulp tester and thermal stimulation were used to assess for pulp vitality of the selected teeth. Additionally, the teeth included in the study did not have irreversible pulpitis symptoms. At the first excavation procedure part of the infected dentin was removed and a calcium hydroxide base was applied and a temporary filling placed. Follow-up time periods

50 35 between 4 and 8 months were accepted as treatment intervals between excavation procedures. The follow-up examinations included clinical evaluation, electric pulp test and radiographies of the stepwise excavation treated tooth (Bjorndal and Thylstrup 1998). In the same study (Bjorndal with Thylstrup, 1998) the dentin color and consistency was recorded after the first excavation, before final excavation and after completion of the final excavation. The demineralized dentin was classified into light yellow, yellow, light brown, dark brown or black. Also the consistency was classified as very soft, soft, medium hard and hard, the latter comparable to unaffected dentin. The recordings made of dentin color and consistency showed that the affected dentin covered by temporary material was significantly browner and less softened after the sealing period. Additionally, after removal of the dark-brownish dentin during the final excavation, the color and consistency of the exposed affected dentin was found to be similar to the excavated peripheral dentin. Nearly 88 % of the total cases presented dentin hardness after the final excavation. According to these findings, Bjorndal and Thylstrup (1998) concluded that the stepwise excavation method is effective in the treatment of deep carious lesions, vs. exposing the pulp if treated by complete caries removal technique. Ten years later Bjorndal explained in his two randomized clinical trials (Bjorndal et al 2010) that given the statistically significant better performance of the stepwise excavation technique, this technique should be preferred for the management of deep carious lesions instead the more complete removal techniques. The first clinical trial ( excavation trial ) was conducted with the purpose of examining differences in the success of stepwise excavation approach vs. direct complete caries excavation in the treatment of deep carious lesions after 1 year of follow-up in adults. The pulp capping trial was conducted to compare the effect of direct capping vs. partial pulpotomy in the treatment of deep carious lesions over the same period of time. The authors proposed that higher success of SW would reduce the likelihood of pulp exposure, thereby reducing the

51 36 risk of endodontic treatment. The sample size of this study (Bjorndal et al., 2010) was 314 adults and consisted of two groups. Patients were selected randomly from centers in Sweden and Denmark to follow either a stepwise excavation group (n=156) or a single complete excavation group (n=158), with 13 and 9 lost to follow- up cases respectively. The clinicians were calibrated by identifying eligible carious lesions using 15 radiographs, which showed different lesion depths. The teeth were selected through radiographs and were also evaluated to confirm a reversible pulpitis diagnose. The allocation sequences for stepwise excavation vs. direct complete excavation were computer generated. After one year of follow- up, clinicians performed radiographic and clinical evaluations of these treated teeth. A tooth was classified as a success when pulp vitality was confirmed without apical radiolucency at 1 year of follow- up. In cases where there was pulp exposure, these patients were assigned randomly to either a direct capping technique or partial pulpotomy, with 22 and 29 cases respectively (Bjorndal et al 2010). The authors reported a significantly better success rate (74.1%) for stepwise excavation approach at 1 year of follow-up vs. a direct complete excavation approach (62.4%), when considering unexposed pulps with confirmed pulp vitality and without apical radiolucency (p= 0.044). In this trial Bjorndal et al., concluded that step-wise excavation resulted in 11.4% fewer cases of pulp exposure and 11.7% more cases were successful. The authors discussed that the treatment effects could have been overestimated if the operators performed less invasive caries elimination. Also, the age of the patient could also have influenced the treatment results. For instance, younger patients were associated with higher proportion of vital pulps without apical radiolucency. The last limitation is that this study was conducted using teeth with deep carious lesions but the health status of each pulp at the time of the treatment was unknown. This means that the researchers assessed the pulp vitality by using thermal stimulation and radiographic exams, but the tooth could have had a pre-treatment

52 37 condition such as pulpal deterioration. Finally, in this study, Bjorndal et al (2010) compared stepwise procedures with conventional caries removal technique, obtaining better results and increased levels of pulp vitality with the stepwise approach, thus demonstrating the internal validity of this study. Another clinical trial by the same author (Bjorndal et al., 1997) was conducted in 31 teeth with deep carious lesions where it was considered whether pulp exposure would result if lesions were treated with one step caries removal. The main objectives of this study were to examine changes in the flora before and after the final excavation after stepwise excavation, with treatment intervals between 6 and 12 months, and to investigate if these changes were associated with clinical dentin alterations. These teeth were treated with the stepwise excavation technique; removing all central cariogenic biomass, necrotic and demineralized dentin (Bjorndal et al 1997). Dentin and color consistency were assessed after the first excavation followed by sealing with temporary restoration. The dentin color and consistency were assessed again after treatment intervals of 6 to 9 months and 9 to 12 months. Clinical recordings were made after the first excavation, after removal of the temporary filling and after the final excavation. The color of demineralized dentin was classified into light yellow, yellow, light brown, dark brown and black dentin. The consistency was classified into very soft, soft, medium hard, and hard. Hard dentin was comparable to sound dentin. The independent variables were treatment time intervals (after first excavation, before and after final excavation) and the dependent variables were dentin color (light yellow, yellow, light brown, dark brown and Black), dentin surface consistency (very soft, soft, medium hard, hard) and bacteriological growth before and after final excavation. In the study, (Bjorndal et al., 1997) 19 teeth with deep carious lesions were randomly selected after the treatment interval and after final excavation to get the microbiological dentin samples. Microbiological dentin samples were obtained from the central demineralized dentin that was residual after first excavation and before application of the temporary filling. The

53 38 results showed that 87% of the teeth changed from very-soft/soft/medium-hard to hard dentin surface after the final excavation, and six samples of central demineralized dentin were found before final excavation without any cultivable flora, increasing to 9 samples after the final excavation. In addition to hardness of dentin surface, the comparison of the microbiological results showed a marked decrease in median growth of bacterial colonies after final excavation compared to before the final excavation. Therefore, the results showed that the hardness of dentin after final excavation was associated with marked reduction in bacterial growth. Another finding was that there was no bacterial pulpal penetration in spite of the presence of bacteria in the excavated dentin in the lesions, which shows that the initial removal of infected dentin is essential for control of caries progression. Thus, the main finding of this study was that dentin changes that occurred during stepwise excavation increased hardness of the dentin which was associated with a marked reduction in bacterial growth after the final excavation. This provides evidence that the stepwise excavation technique is effective in the treatment of deep carious lesions. However, the study lacked information about species-specific bacterial findings and regarding statistical procedures which would be necessary to repeat the study, suggesting that a confirmatory study would be of interest. For instance, the bacterial growth after the final excavation was not quantified in type specie/quantity and correlated to dentin changes that occurred during stepwise excavation (hardness of dentin surface). A clinical trial with the objective of assessing the radiographic changes associated with incomplete removal of carious dentin was accomplished by Oliveira et al (2006). The main objective of the study was to evaluate the long-term effect of incomplete removal of carious dentin and restoration of teeth for a period of months. At the same time, this study evaluated the mineral content of the remaining carious dentin in each tooth. Results demonstrated the inactivation of the carious process after incomplete carious tissue removal and sealing, and also showed that bacteria sealed inside cavities

54 39 are not harmful to tooth structure since they are isolated from the oral environment. The sample in this study consisted of 32 permanent posterior teeth from 27 patients with deep carious lesions. These patients were from 12 to 23 years of age. Teeth selected had to be at risk of pulp exposure if the demineralized dentin was eliminated completely. The teeth that were selected did not have spontaneous or percussion pain or periapical pathology. At 6-7 months after sealing the cavity, only sensitivity tests, like thermal stimulation, were done to evaluate pulp vitality in teeth. Then, after 6-7 months the radiographs were assessed to determine if teeth had periapical integrity and for changes in the radiolucent Zone (RZ) that was defined as the amount of demineralized dentin remaining. The control areas (CA) were determined as dentinal areas (mesial and distal) close to the RZ. Change in the density measurement of the RZ during treatment was evaluated using a blinded design through digital subtraction of radiographic images in relation to the initial exams in the two experimental periods (6 7 and months). The difference in radiographic density between the two radiographs was determined for each selected area using a grey tonalities scale. The independent variables in this study were the treatment intervals at 6-7 months and months. The dependent variables were radiolucent zone (RZ) depth, tertiary dentin formation and the changes in radiographic density in RZ (radiolucent zone). In the study the authors determined the tertiary dentin formation as the mineral increase. Student t-test, analysis of variance and Turkey s multiple comparison tests were used to measure and compare the means of the control areas and RZ zones. The authors of this study reported that subtraction of the RZ showed grey levels higher than 128, which suggests that there was mineralization. Also, the authors reported that the subtraction values of the control areas differed from those of the RZ (p<0.001). They did not observe differences in the radiographic density of the control areas between the two experimental periods (p> 0.05). The same situation was observed for the RZ. The

55 40 subtraction radiographic images indicated zone mineralization of residual sealed decalcified dentin after a period of months. These results suggested that the mineral change (mineralization) took place in the 6 to 7months interval. At the end, the authors pointed out that the sealing of the cavity after partial caries removal in teeth for a period of months caused increases in radiographic opacity of the radiolucent zone, which suggests that in these lesions there was arresting of the lesion progression. Unfortunately, in this study (Oliveira et al., 2006), pulp vitality outcomes were not reported. Another point is that the reliability of this study depended on the digital radiographic image subtraction that has many variables involved in the image acquisition. Finally, the authors concluded that complete dentin caries removal does not seem to be essential to control caries progression and they generalized this conclusion to all teeth with deep carious lesion. In the discussion of Bjorndal et al. (2010), the authors suggested that further research should be done to investigate the result of leaving a small amount of carious dentin, which is arrested. This approach would avoid re-entry of the cavity and should be considered with the purpose of preventing pulp exposure. Currently, this approach is known as partial caries removal, as mentioned by Rickkets and E.Kidd (2009) and Thompson et al. (2008). Following the same concept of partial caries removal, Maltz et al. (2007) explained that in the literature several studies showed that the complete removal of the infected dentin of a carious lesion is not essential to arrest the cariogenic process. Rickkets and Kidd (2009) and Thompson (2008), Maltz et al. (2007) proposed that the the partial caries removal approach was a good alternative to treat deep carious lesions. A study by Maltz et al. (2007) was conducted with the purpose to evaluate the radiolucency depth and tertiary dentin deposition in teeth that were treated with partial caries removal approach. The sample of the study consisted of 32 permanent posterior teeth with deep carious lesions from 27 patients of 12 to 23 years old, where lesion depth

56 41 was < 2/3 of the dentin thickness assessed radiographically. Radiolucent zone (RZ) depth and tertiary dentin formation were assessed qualitatively. In this study, the changes in radiographic density in RZ and control areas (CA) were estimated quantitatively. Followup examinations were made to assess the lesions at 6-7, and months. At the same time, the radiographic images from the beginning of treatment were qualitatively compared to those taken at 6-7, and months. The results of this study showed increased radiopacity in the first 6 7 months and no change in radiopacity between 6 7 and months, decrease in RZ depth and deposition of tertiary dentin. In this study, Maltz et al. (2007), concluded that the partial removal of carious dentin and sealing of the cavity for a period of months, stimulated pulpal defense reactions producing the arresting of the carious process. Other conservative caries removal techniques and further research In recent years the treatment of caries in dentistry has been directed towards more conservative methods and more preventive techniques. Literature shows that the complete removal of the infected dentin of a carious lesion is not essential to arrest a cariogenic process. Maltz et al. (2007) and Maltz and Garcia (2012) provided evidence that it is not necessary to reopen the cavity as advocated in the stepwise excavation approach. Maltz and Garcia (2012) conducted a study to compare partial caries removal and stepwise excavation approach in the treatment of deep carious lesions with respect to the primary outcome of pulp vitality over a 3-year follow-up period. The authors concluded that there is no need to re-open a cavity and perform a second excavation for pulp vitality to be preserved because partial dentin removal showed a statistically significant improvement with regards to the maintenance of pulp vitality as compared with Stepwise after the 3-year follow-up period.

57 42 Likewise, Maltz s most recent study (Maltz et al., (2012b) also assessed the effectiveness of partial removal of carious dentin and restoration in a single appointment compared to stepwise excavation (SW) in an 18-month study. This recent study was a multicenter randomized clinical trial that evaluated the effectiveness of partial removal of carious dentin and restoration in a single appointment compared to SW excavation in association with different variables including age of patient, gender and family income and tooth specific variables such as restorative material, number of surfaces of restoration, time to complete the restoration, and size of the cavity. The target population in this study included patients who were more than 6 years old who had permanent molars with deep carious lesions having a radiolucency halfway or more into dentin (Maltz et al., 2012b). Patients were selected on the basis of having teeth with pulp vitality and reporting absence of spontaneous pain, positive percussion test, and absence of periapical alterations (Maltz et al., 2012b). The patients were allocated to either a partial caries removal group, which was the test group and to the stepwise excavation group, which was assigned as the control group. Clinical and radiological exams were completed after a mean time of 18 months follow-up. The main outcome of this study was pulp sensitivity to cold test and absence of periapical radiolucencies, which was also defined as success of both treatments. In this study correlations between the studied variables and outcomes were analyzed by logistic regression. The trial included 233 patients: 78% received 1 treatment, 18% received 2 treatments and 4% received 3 or more treatments (Maltz et al., 2012b). The results showed that after 18 months of follow-up, partial caries removal was more successful than SW excavation in preserving pulp vitality. Regression analysis indicated no associations between treatment success and the variables studied thus indicating that variables including age, gender, family income, filling material, and numbers of surfaces of the restoration were not correlated with treatment success.

58 43 Most studies show a high rate of success regarding quality (Leksell et al., 1996; Bjorndal and Thylstrup, 1998; Bjorndal et al 2010) and survival of restorations after 2 years (Maltz et al., 2012b), regardless of the number of surfaces involved in the cavity and restoration. Maltz et al., (2011) did not find association between the number of surfaces involved and the success of the partial caries removal treatment after 18 months follow-up. But, in this same study all failure cases (n=10) were class II restorations, whereas from the 16 success cases, 12 presented class I restorations (Maltz et al, 2012b). The age variable is another interesting finding in the Maltz et al 2012b study. The participants mean age was 17 years. The authors thought age would be a significant factor for successful outcome since it was postulated that in stepwise excavation the age is considered an important factor variable for treatment success and is worthy to be studied because of the pulp cells response is more active in younger teeth (Murray et al 2002). However, Maltz et al. (2012b) reported that the age of the patients was not a determinant factor for successful outcome; since the patients in whom failures occurred in this study were between 6 and 53 years old (Maltz et al., 2012b). In spite of all the literature demonstrating that partial caries removal and stepwise excavation are effective techniques, these approaches still have detractors. As mentioned before, Kidd et al. (1996) reported that most dental schools still teach that all stains should be removed from the dentinal tissue even though many authors have reported that leaving stains is more conservative. Kidd et al. (1996) also reports that the point where the excavation of caries is finished varies according to country, dental school and teaching philosophy. Weber s study assessed the treatment decisions about deep carious lesions in the Public Health Service of the city of Porto Alegre, Brazil. The authors of this study conclude that the treatment decisions were influenced by the year of college graduation of dentists. Weber found that younger dentists tended to utilize more conservative approaches, such as stepwise excavation, compared with those indicated by older

59 44 dentists. Also, the traditional procedure, complete caries removal technique, is still the one dominating the decisions of most dentists. Weber et al. (2011) explains that the rationale of complete caries removal is to prevent the advance of caries and to provide a sound and mineralized dentin as a base to restore. Also, Weber et al., 2011 states that there are some approaches for the treatment of deep carious lesions such as stepwise excavation, indirect pulp capping and partial caries removal, which should be indicated in order to preserve the pulp-dentin organ complex. Need of further randomized clinical trials There are several questions that have not been answered in conservative removal techniques research such as: How much caries tissue can be left? How can we assess the amount of remaining carious tissue? (E.Kidd 2004) How does remaining caries tissue affect physical properties of materials? What is the bonding quality to caries affected dentin? (Schwendicke et al., 2013). An important issue is that in many studies the amount of carious tissue left or removed varies significantly. Often it is not quantified or adequately described. Further research is important to provide evidence-based decision making in our treatment of deep carious lesions. Another important consideration is that most conservative removal techniques studies show a high risk of bias. Overall, randomization procedures are not well described; follow-up times and the use of different restorative material are different in each study (Bjorndal 2011). Restorative materials for temporary and definitive materials include calcium hydroxide, zinc oxide, eugenol, amalgam, glass ionomer and resin composite. It is difficult to perform qualitative analysis using information from studies with different clinical designs, materials and outcome measures. To answer such questions, we will need more calibrated, multi-centered randomized studies (Schwendicke et al 2013). Also we will need to perform long-term trials with

60 45 standardized materials and time intervals in order to have less risk of bias (Schwendicke et al 2013). Summary of Literature Review Several articles have been reviewed which describe and apply different conservative techniques for management of deep carious lesions. From these studies, evidence strongly suggests that methods such as stepwise excavation are superior to the conventional ones in maintaining pulp vitality in the treatment of deep carious lesions, opening a window for new research to further explore these methods. Despite being effective techniques, there have been a great variety of methodologies; patient population, operator background, materials and measurements used which may account for large differences in the success rate between different studies. This seems to be an area that requires further standardization of studies to better interpret the results. Another gap is a lack of studies in American clinics or hospitals where most clinicians perform complete caries removal. A good starting point would be to perform these studies in an educational setting, which is needed to spread the knowledge of these conservative techniques to younger dentists to start shifting the paradigms about the established successful caries removal methods. The stepwise excavation caries removal procedure represents an important alternative to treating deep carious lesions in order to prevent a pulp exposure and maintain the tooth vitality. Success rate is generally high in stepwise excavation technique studies (Bjorndal et al. (1997); Bjorndal and Thylstrup (1998); Bjorndal et al. (2010); Maltz et al 2012b), with values reported from 74.1 to 86 %. Most of these stepwise excavation studies were done in permanent teeth with a diagnosis of deep carious lesions. An important point in all of these studies is the fact that most of them did not have a comparison group. Furthermore, another aspect is that there was no definition as to how much carious dentin was removed.

61 46 Therefore, comparing studies with different methodologies makes it difficult to standardized results and make general conclusions. It is important to evaluate the outcomes and demographic variables with more detailed criteria, establishing age, pulp vitality, restorative material and outcome of treatment success. Also it is important to compare the variables associated with procedures that were re-evaluated and those that were lost to follow-up after a stepwise excavation procedure. A retrospective study that would assess the proportion of patients that wereevaluated and re-entered after a stepwise excavation procedure would be an important contribution to the dentistry field. As described in the next chapter, the present study will assess the proportion of patients that had a stepwise excavation procedure re-evaluated at The University of Iowa College of Dentistry between 2004 and Subsequently, to evaluate the association between different variables and whether the tooth treated with stepwise excavation procedure was re-evaluated, data such as patient age, gender, number of miles traveled, size of restoration, type of provider and tooth arch position were collected and analyzed. Additionally, this study will evaluate clinical outcomes of stepwise excavation completed treatments. This study will contribute to the dentistry field by assessing the proportion of stepwise excavation procedures for the treatment of deep carious lesions and to analyze demographic factors and tooth specific characteristics in their association with completion outcome of re-evaluation/re-entry of stepwise excavation caries removal procedure.

62 47 CHAPTER III MATERIAL AND METHODS Overview of methods This study provides significant information on the patient profiles of those who receive stepwise caries excavation procedure at the University of Iowa College of Dentistry as well as preliminary data for planning future studies. The main purpose of this study was to evaluate the proportion of patients that were re-evaluated and re-entered after the first appointment of a stepwise excavation procedure. The secondary purpose was to analyze demographic factors and tooth specific characteristics to determine their association with whether the stepwise excavation procedure was re-evaluated or not after the first appointment. This chapter covers the research questions, general and specific objectives, the important operational definitions, inclusion and exclusion criteria, first and second phase of the study explanation, Institutional Review Board information (IRB), description of the stepwise excavation technique, and detailed explanation of data extraction and statistical analyses techniques used to investigate the stated research questions. Main Research question What is the proportion of patients that had a stepwise excavation procedure reevaluated/re-entered at the University Of Iowa College Of Dentistry between 2004 and 2012? Sub-questions 1. What is the proportion of stepwise excavation procedures that were reevaluated/re-entered at the University Of Iowa College Of Dentistry during the time period?

63 48 2. What is the association between patient demographics and whether the tooth was re-evaluated or not after the first appointment at the University Of Iowa College Of Dentistry during ? 3. What is the association between tooth specific variables and whether the tooth was re-evaluated or not after the first appointment at the University Of Iowa College Of Dentistry during the time period? 4. What are the clinical procedures performed and re-entered of teeth treated with a stepwise excavation procedure completed at The University of Iowa College Of Dentistry during ? Main Purpose: To evaluate the proportion of patients that had a stepwise excavation procedure and were re-evaluated and re-entered. To identify characteristics associated with completion of re-evaluation/re-entry within 18 months. Secondary Purposes 1. To assess the associations between demographic factors and whether the tooth treated with stepwise excavation procedure was re-evaluated. 2. To assess the associations between tooth specific variables and whether the tooth treated with stepwise excavation procedure was re-evaluated. Main Expected Finding Most of the stepwise excavation procedures performed at The University of Iowa College of Dentistry, between 2004 and 2012 were re-evaluated and re-entered.

64 49 Specific Expected Findings 1. The proportion of teeth with stepwise excavation procedures that were never reevaluated or had a re-entry appointment was less than the teeth that were reentered/re-evaluated (i.e., re-evaluated teeth were more than 50% of the total). 2. Most patients who had teeth treated with stepwise excavation procedures kept reentry appointments within an average time of 6-12 months. 3. Most teeth treated with stepwise excavation procedure were restored with a direct restoration such as amalgam, direct resin composite, glass ionomer, sedative filling or an indirect restoration, such as crown or inlays/onlays. General Objectives: 1. Evaluate the proportion of patients that had a stepwise excavation procedure that were re-evaluated and re-entered (re-entry status) at the University of Iowa College of Dentistry (UICOD) from January 2004 to December Evaluate the association between re-entry status patient demographics. 3. Evaluate the association between re-entry status tooth characteristics. Specific Objectives 1. To assess the percentage of teeth treated with stepwise excavation procedure that had re-entry appointments/procedure. 2. To assess the percentage of teeth that had stepwise excavation procedure and were never reevaluated. 3. To assess the association between the age of the patients and whether the tooth was re-evaluated after the first appointment of the stepwise excavation procedure.

65 50 4. To assess the association between patient s gender (male or female) and whether the tooth was re-evaluated or not after the first appointment of the stepwise excavation procedure 5. To assess the association between types of health provider (faculty, graduate student, and pre-doctoral student) and whether the tooth was re-evaluated after the first appointment of the stepwise excavation procedure 6. To assess the association between the number of tooth surfaces restored and whether the tooth was re-evaluated or not after the first appointment of the stepwise excavation procedure 7. To assess the association between different tooth type (central incisor, lateral incisor, canine, molars or premolars) and whether the tooth was re-evaluated or not after the first appointment of the stepwise excavation procedure 8. To assess the association between tooth arch (maxillary or mandibular) and whether the tooth was re-evaluated after the first appointment of the stepwise excavation procedure 9. To assess the association between total number of recall exams before SWP was completed and whether the tooth was re-evaluated after the first appointment of the stepwise excavation procedure. 10. To assess the association between number of miles that patient traveled to the UICOD and whether the tooth was re-evaluated or not after the first appointment of the stepwise excavation procedure. 11. To assess the association between the type of dental insurance of the patient at the time of the SWP and whether the tooth was re-evaluated after the first appointment of the stepwise excavation procedure. 12. To assess the clinical outcomes of teeth treated with a stepwise excavation procedure completed at The University of Iowa College Of Dentistry during

66 51 Definition of Variables Dependent Variable: The primary outcome status (dependent variable) was defined in terms of whether or not there was completion of re-evaluation/re-entry within 18 months of the stepwise excavation procedure (Re-entry status). Thus, the dependent variable in this study was the re-evaluation/re-entry at 18 months of the stepwise excavation procedure. Independent Variables The independent variables collected in this study included patient demographic factors: (gender, age, number of general oral hygiene recall visits, number of appointments at the UICOD within 18 months, number of months for re-entry/recall appointment within 18 months (in days), number of miles that the patient travels to the UICOD and type of dental insurance at the time of SWP. Independent variables also included the following stepwise excavation treated tooth specific variables: tooth type, tooth arch, number of surfaces treated, type of provider that performed stepwise procedure (pre-doctoral, graduate student or faculty), clinical outcomes such as type of final restoration (glass ionomer, amalgam, resin composite, sedative fillings, inlays/onlays and crowns), root canal treatment and tooth extraction, number of surfaces of final restoration and type of provider that performed final restoration. Of the independent variables the categorical variables included gender (male and female), type of dental insurance (dental insurance, self-pay and Medicaid), tooth arch (maxillary and mandibular), tooth type (incisor, canine, premolar and molar) and type of provider that performed SWP (faculty, graduate student and undergraduate student). Continuous variables included: age, number of miles traveling to UICOD and number of months at the appointment re-entry interval. Discrete variables included total number of

67 52 recall exams, total number of patient appointments, total number of restorations per patient, number of surfaces at the SWP 1 st appointment and number of surfaces of the final restoration. Independent variables are presented in Table A1and A2. Data regarding the types of outcomes after stepwise excavation procedure were reported. Then categories of clinical outcomes were created as displayed in Figure 6. The categories were: 1) Direct restoration/ indirect restoration (composite, glass ionomer, amalgam/ crown, onlay); 2) root canal treatment or 3) tooth extraction. The restorative procedure codes that were included in this study are presented in Table B1 to B10. Root canal treatment (root canal therapy) and tooth extraction treatment codes are presented in the table B11, B12, B13 and B14. Operational Definitions 1. Axium Chart Number: Number that is assigned to each patient at the entry into the UICOD and uniquely identifies a patient in the dental college AxiUm system. 2. Axium System: The Electronic Health Dental Record management software used at The University of Iowa College of Dentistry. 3. Date of treatment code: It was used to determine the timing of stepwise excavation treatment and re-entry appointment. Measurement unit: date. 4. Dental Restoration: Material used by provider to restore the prepared tooth structure at the final restoration placement. 5. Dental Provider: the clinician who performed the stepwise excavation procedure and the final restoration. The operators are categorized as pre-doctoral student, graduate resident and faculty. 6. Stepwise Excavation Procedure (SWP): two-steps incomplete caries removal approach where the carious dentin tissue is incompletely removed at the first step and is left in proximity to the pulp under a temporary filling (Schwendicke et al.,

68 ). Then a long -term transitional restorative material (i.e: Glass Ionomer) is used to seal the cavity preparation and allow time for the pulpal-dentinal complex response. In the second step (second visit) 6 to 12 months later, a re-entry procedure is accomplished, complete removal of all carious tissue and a definitive restoration are performed (Schwendicke et al., 2013). 7. Patient Age: Age in years as measured from the date of birth of each patient to the date the stepwise procedure was accomplished. 8. Patient Gender: Male or Female. 9. Tooth extraction (TE): extraction procedure of a stepwise excavation treated tooth as consequence of an irreversible pulpitis process or pulp exposure during reentry appointment or non-restorability. 10. Tooth Number: Used to determine the tooth type and arch of the tooth treated with stepwise (maxillary or mandibular). In this study we will use the universal tooth numbering system (Fuller et al., 1977). 11. First appointment of SWP or first treatment date: First step of stepwise excavation procedure where the carious dentin tissue is incompletely removed and left in proximity to the pulp under a temporary filling. 12. Re-entry status: represents the primary outcome which was defined in terms of whether or not there was completion of re-evaluation/re-entry within 18 months of the SWP. 13. Re-entry appointment: Second step or second appointment of stepwise excavation procedure where a complete removal of all carious tissue is performed and a definitive restoration is placed. 14. Subsequent treatment: Any dental procedure on the treated teeth received after stepwise procedure was performed such as amalgam, resin composite, glass ionomer, sedative filling, inlay/onlay and crown, root canal treatment and tooth extraction. This is defined in tables B1 to B14.

69 Root canal treatment (RCT): Endodontic treatment of a stepwise excavation treated tooth as consequence of pulp exposure during re-entry appointment or irreversible pulpitis process. Study design Recorded data of current patients who had stepwise excavation procedures in any of their teeth between January 2004 and December 2012 was analyzed retrospectively using the Electronic Health Record (EHR-Axium) at the University of Iowa College of Dentistry, as shown in Figure 6. The final date for data collection was December 31th, 2012 therefore this assured that all procedures had a minimum of 18 months of followup. All the data used in the outcomes analysis was obtained from EHR-Axium database. Figure 6. Flow chart for study design. All procedures were followed for 18 months.

70 55 Sample Size: This study utilized a sample of stepwise excavation procedures from a group of patients from the University of Iowa College of Dentistry (UICOD). The sample size was 1985 stepwise excavation procedures (1326 patients). The data for this study included the first stepwise excavation procedure completed per patient at the College of Dentistry from January 2004 to December Population: This study evaluated data from patients who were not less than 18 years of age at the first treatment up to a maximum of 65 years of age. Only patients with the specific code of stepwise excavation procedure ( ) were included in the study. Inclusion criteria: 1. Patients that had at least one stepwise excavation procedure from January 2004 to December Patients not less than 18 years of age up to 65 years of age. (Patients less than 18 years of age were excluded because we disregarded the patients seen at the Pediatric dentistry clinic UICOD) Pilot Study Objectives 1. To determine the precise amount of completed stepwise excavation procedures that was accomplished between 2004 and Estimated at approximately 2600 treatments. 2. To determine the stepwise excavation procedures which were re-entered/reevaluated. 3. To select which procedures would be included in the study. 4. To decide what variables to include in the study.

71 56 Pilot Study The pilot study used the computerized database from the UICOD. This pilot determined the precise number of completed stepwise excavation procedures that were accomplished between the 2004 and 2012 period during the first phase of the study, it was determined what stepwise excavation procedures were successfully re-entered/reevaluated in order to select which patients would be involved in the study and it was decided what variables would be finally included. Patients with stepwise excavation procedures that were not completed or that did not return were included in the main results and their percentage was documented. In this phase of the study the patient s Axium electronic health record and their archived records were also evaluated in order to decide what outcomes were to be included. Patient information was obtained from the UICOD data base search and included: Axium Chart number, treated tooth number, age in which the first visit of the stepwise procedure was performed, gender, and number of visits, number of miles traveled to UICOD, type of dental insurance, type of provider who completed the treatment (predoctoral, graduate, faculty), number of surfaces. Also, information as the type of tooth (premolar, molar, incisors), tooth arch (maxillar or mandibular), and number of surfaces restored were linked to an axium patient chart number and these were documented. The Axium Chart number and the treated tooth number were also used to identify the second visit or re-entry/ re-evaluation appointment as well as the clinical outcome completed after stepwise excavation procedure was re-evaluated and re-entered. These included direct restorations (resin composite, amalgam, sedative filling, and glass ionomer), indirect restorations (inlay or onlay, crown), tooth extractions and root canal treatment. The Axium chart patient number and visit recalls and types of visits were used to identify all the recall appointments that were included and prophy appointments to evaluate the oral hygiene of the patient. Also the number of all appointments within 18

72 57 months provided information to identify all the patients appointments at the UICOD in different departments. Table B15 displays the codes to determine the recall and prophylaxis visits. Institutional Review Board Information (IRB) This study required University of Iowa Institutional Review Board approval. The principal investigator (graduate student) was responsible for preparing the forms and documents required for the IRB application. The application was submitted through the Hawk IRB online site. Data extraction started only after IRB approval of the study was received (IRB identification # ) Data Extraction Methods Figure 7 shows a summary of the extraction methods for stepwise excavation procedures between July 2004 and December Each treated tooth that had a stepwise excavation procedure was linked to a patient s axium number. Only patients with the specific code of stepwise excavation procedure ( ) were involved in the study. Patients that had at least one stepwise excavation procedure between January 2004 and December 2012, with an age between years old were selected. Initially it was estimated that there would be 2600 stepwise excavation procedures to evaluate. After exclusion based on age criteria, there remained 2037 stepwise excavation procedure for evaluation. Patient information was obtained from the UICOD data base search and included: Axium chart number, age in which the first visit of the stepwise procedure was performed, gender, state and city where the patient came from and number of miles to travel to UICOD (driving distance was calculated based upon the zip code of the residential address provided by the patient and the zip code of the UICOD using Google Maps API). Also type of dental insurance at the time of stepwise excavation procedure, type of patient appointment at the UICOD, total number of

73 58 restorations per patient at the UICOD in the 18 months prior to the stepwise excavation procedure, interval in months between the first stepwise and re-entry appointment, and total number of recall exam and prophy visits. Tooth information obtained from the patient record included: treated tooth number (which was used to determine tooth type and tooth arch), number of surfaces in the treated tooth. Additionally, type of provider who accomplished the treatment (pre- doctoral, graduate, faculty), and type of final restoration placed at the re-entry appointment, number of surfaces and type of provider who completed the final restoration was collected from the Axium chart. Figure 7. Flow diagram detailing data filtering and follow-up for 18 months. The information from these study variables was linked to an Axium chart patient s number and also documented in an excel spreadsheet. In this first phase of the

74 59 study, it was observed that surfaces were reported only from 2008 forward. Before that date there are no surfaces reported on the stepwise excavation procedures collected for this study. The Axium Chart number and the number of the selected tooth were also used to identify the second visit and any re-entry appointments related to these procedures as well as the type of final restoration, root canal treatment or tooth extraction received on the treated tooth after stepwise excavation procedure. The Axium chart patient number and appointment recalls and type of patient appointment was used to identify all the recall appointments for exam and prophylaxis prior to the SWP to evaluate the oral hygiene of the patient and compliance. The Axium chart number was used to identify all the patients appointments at the UICOD in different departments to evaluate patient compliance. Patients with stepwise excavation procedures that were not completed or that did not return were included for the outcome analysis and their percentage was documented. To assure the internal validity of this study, a random review of 50 records per year from 2004 to 2012 was completed to determine if the stepwise excavation procedure followed the University of Iowa Clinical Guidelines. Table C1, presents the clinical recommendations for stepwise excavation of the College of Dentistry from The University of Iowa. The total number of SWP that resulted in a RCT and TE (root canal treatment and tooth extraction) clinical outcomes were reviewed by reading the records to verify if these were actually SWP. A total of 1,985 stepwise excavation procedures were obtained after this review. A total of 1,326 patients participated in this study. A single SWP was selected per patient in order to perform statistical analyses and to have independence between variables. The SWP used in these analyses was the first performed for that patient at the UI College of Dentistry during the study period, Then, a follow-up of the patient outcomes up to 18 months, starting from the SWP 1 st appointment date was made to analyze all

75 60 procedures using the same time frame and to assess what proportion of SWP procedures were re-evaluated and re-entered. The primary outcome status was defined in terms of whether or not there was completion of re-evaluation/re-entry within 18 months of the SWP. Additional description of clinical outcomes among SWP for which re-entry was completed was also reported. Restorations including glass ionomer, resin composite, amalgam, sedative filling, inlay, onlay and crown were considered as restorative outcomes if the stepwise excavation treated tooth did not receive prior root canal treatment or implant. For instance, if a stepwise excavation treated tooth received a root canal treatment and subsequently a crown was placed, it was classified as root canal treatment outcome. Root canal treatment and tooth extractions were considered as clinical outcomes. Stepwise excavation treated teeth that reported root canal therapy steps codes were considered as root canal treatment procedures. Likewise, stepwise excavation treated teeth that reported crown step codes were considered as crown restorations. For instance, temporary crown steps were considered as crown procedures. Sedative fillings were also considered as restorative outcomes even if they were not removed in the re-entry appointment. These cases were reported in a different column as sedative fillings restorations. Patient information was obtained from the UICOD data base search and was displayed in a new excel spreadsheet. Statistical Methods In this study descriptive statistics were conducted to evaluate the number of patients that had a stepwise excavation procedure and the proportion that was not reevaluated vs. those that were re-evaluated and re-entered. Likewise, teeth which were

76 61 restored with direct or indirect restorations, root canal treatment and tooth extractions were reported as clinical outcomes. Demographic and tooth specific variables were collected and analyzed for evaluation of their association with the outcome of interest (re-entry status).to accomplish this, logistic regression analysis was used, since this predicts the outcome of categorical dependent variable ( re-entry vs. no re-entry). Data were summarized using frequency tables and cross-tabulations as well as summary statistics and graphics. The outcome of interest was re-entry status of SWP (whether or not re-entry and re-evaluation was completed within 18 months). Different demographic and tooth specific variables were also analyzed for evaluation of their association with completion of re-evaluation/re-entry. Bivariate relationships of categorical covariates with this outcome were assessed using chi-square tests of association; relationships of quantitative variables with this outcome were assessed using the Wilcoxon Rank Sum test. Additional relationships were explored using the approaches above as well as Spearman rank correlations. Multiple logistic regression methods were used to evaluate the association of multiple independent variables with completion of re-evaluation/re-entry. A 0.05 level of statistical significance was used throughout. Data were analyzed with SAS Version 9.3. Multiple logistic regression modeling was used to model the probability that reevaluation/re-entry was completed within 18 months of the performance of the SWP and to identify those factors significantly associated with the probability of re-entry. Explanatory variables considered included: gender, age and insurance status of the patient, driving distance to the UICOD, provider level (faculty, resident, or undergraduate), the tooth type and arch of the SWP, the number of recall or prophy visits in the 18 months prior to the performance of the SWP, the number of restorations at the UI COD in the 18 months prior to the SWP, and the year in which the SWP was performed. Forward, backward, and stepwise model selection methods were all

77 62 considered during the process of selecting the final model, and the Akaike s Information Criterion (AIC) was used to choose among alternative model formulations. All firstorder interactions (interactions between all possible pairs of covariates) were also considered. Selection Methods for Logistic Regression Model Forward selection The first step of this selection method consisted of making a simple model with one explanatory variable which provided the best the square of the correlation coefficient, when compared with all other models with only one variable. In the second step, a second variable was added to the existing model if it was better than any other variable at explaining the remaining variability and produced a model which was significantly better than that in the previous step. This process was repeated progressively until the addition of a further variable did not significantly improve the model. Backwards selection The first step was to generate the full model which included all the variables. The next step was to remove the least significant variable from the model, and retain this reduced model if it was not significantly worse than the model in the previous step. This process was repeated progressively, stopping when the removal of a variable is significantly detrimental Stepwise selection This selection method was a combination of forwards and backwards selection. It was similar to forward selection but it allowed variables which had been included in the model to be removed, by checking that all of the included variables that were still required (Petrie et al., 2006).

78 63 Graphical displays were generated to illustrate the impact of significant covariates on the probability of re-entry within 18 months. The level of significance was set at Lack of fit was assessed using the Hosmer and Lemeshow goodness of fit test.

79 64 CHAPTER IV RESULTS Overview The main purpose of this study was to compare characteristics associated with the re-entry status (re-evaluation/re-entry vs. no-evaluation/no re-entry) of teeth within 18 months of having the initial step of stepwise excavation procedure (SWP). Data filtering This study initially projected to evaluate 2600 SWPs performed between 2004 and 2012 at the University of Iowa, College of Dentistry (UICOD). Of the 2600 SWPs, 2037 SWPs were selected after applying the age inclusion criteria. Also, a detailed review of the procedures that resulted in a root canal treatment or a tooth extraction was accomplished to exclude the procedures that did not follow the UICOD stepwise excavation guidelines. This resulted in a final number of SWPs of 1985 procedures. Of these 1985 SWPs, there were 975 SWPs re-evaluated at any point in time over the 8 years. The 1985 SWPs were performed in 1,326 patients. For statistical analyses, a single SWP was selected per patient in order to have independence between variables. The SWP used in these analyses was the first performed for that patient at the UICOD during the study period. Starting from the SWP 1st appointment date, the SWP tooth was followed for 18 months. This was done to analyze all SWP teeth using the same time frame. Of the 1326 SWPs, 518 were reevaluated/re-entered within the 18 month interval. The number of teeth that were not re-entered/re-evaluated after stepwise excavation procedure was completed in the 18 month window was 808 (61%) which provides valuable information regarding UICOD patient compliance. The study also revealed that from a total of 518 (39%) re-evaluated SWPs, 387 (75%) had a final direct/indirect restorative material placed (additionally, analysis of the restorative outcomes when stepwise excavation procedure was completed showed that 33% (169) corresponded to

80 65 amalgam, 23% (120) to resin composite, 4% (18) corresponded to glass ionomer restorations, 1% (5) to inlays and onlays and 6 % (32) to crowns), 73 (14%) received root canal therapy (RCT) and 58 (11%) were extracted (TE). Of the teeth re-evaluated, within 18 months, 75% avoided needing RCT or TE. Basic Descriptors Basic descriptors per patient Basic descriptive statistics were used to describe patient demographic characteristics and tooth specific variables. Table D1 shows a summary of demographic characteristics per patient while Table D2 displays descriptive statistics for tooth specific variables per patient. The distribution of the number of SWPs performed on the 1,326 patients participating in this study is given below in Table 4. Of the 1,326 patients, 983 (74.1%) had only a single stepwise excavation procedure within the study period. Among the remaining 25.9% of patients, the number of stepwise performed during the study period ranged from 2 to 12. Description of the study population. Ages of the 1,326 patients ranged from 18 to 65 years, with a mean age of 35.7 years and a median age of 31.1 years (Table E1). Figure D1 shows that 46.08% of these procedures were accomplished on patients from 18 to 29 years old, 19.83% from 30 to 39 years old, 15.38% on 40 to 49 years old, 12.97% on 50 to 59 years old and 5.7% on 60 to 65 years old. There are fewer procedures in each interval as the age increases. Table E2 shows that the study population was comprised of 697 females (52.6%) and 628 males (47.4%); the gender of a single patient was unknown (Figure D2).

81 66 Table 4. Distribution of the number of stepwise excavation procedures (SWPs) performed in each of 1,326 patients. # SWPs Frequency Percent Descriptive statistics for the driving distance to the UI College of Dentistry given in Table E1 indicates that the mean distance was 74.4 miles and the median distance was 44.4 miles. Figure D3 shows that most patients came from nearby and medium range distances to UICOD. Figure E1 gives the geographic distribution of the reported zip code of the patient s residence within the U.S.; the dark dot indicates the location of the UI College of Dentistry. Figure E2 gives the geographic distribution of the reported zip code of the patient s residence within a one-state radius of the UICOD. Categorization of the driving distance is listed in Table E12. It may be noted that some of these distances are quite large, so their distribution was further explored, as was the possibility that distance was related to age. Given the magnitude of some of the

82 67 distances, we attempted to consider whether the age of the patient was related to distance, thinking that perhaps, in an academic setting, the address provided by some students might reflect out-of-state permanent residence. However, there was no apparent increasing or decreasing association between patient age and driving distance to the COD (Spearman rank correlation rho=0.01, p=0.61), as seen in Figure E3. In relation to the patient s dental insurance status at time of SWP, 37% had some type of dental insurance (excluding Medicaid), 48% did not have any type of dental insurance (self-pay), and 15% had Medicaid (Table E3 and Figure D4). Frequency tables for gender, type of dental insurance at the time of the SWP, calendar year of treatment, and provider level are given in Tables E2, E3, E4 and E5. Among the 1,326 patients, 518 of them returned to complete re-evaluation/reentry within 18 months. The length of time to re-entry varied from 0.03 to month, with a mean time to re-entry of 6.4 months, and a median time to re-entry of 6.25 months (Table E1). An additional 90 patients returned to the UICOD for re-evaluation/re-entry of the SWP, but not within the 18 month time frame used in these analyses. The re-entry of these patients SWPs took place as much as 73.7 months after the SWP was performed; while 718 patients never returned. If the total of 608 patients who ever returned for completion of re-evaluation/re-entry is considered, regardless of whether they were within the 18-month window, the range of time to re-entry was 0.03 to 73.7 months, with a mean time to return of 10.3 months, and a median time to return of 7.1 months (Table E1). Additional clinical data collected included the total number of recall examinations and prophy visits in the 18 months prior to the SWP, and the total number of restorations at the UICOD in the 18 months prior to the SWP and these are displayed in Table E9 and E10.These variables are summarized through the frequency Table E11 and also via descriptive statistics. For the total number of recalls exams and prophy visits 18 months

83 68 before the SWP was accomplished, 64% of procedures correspond to patients that had zero recall exam, 16% of the procedures correspond to patients that had one recall exam, 12% were associated with patients that had two recalls and 8 % to patients that had more than 3 recall exams (Figure D5). For the total number of restorations per patient 18 months before the SW procedure was accomplished, 64% had no restorations placed, 17% had one restoration, 8 % had 2 restorations placed and 11% had more than three restorations placed (Figure D6). Tooth Specific Study Variables per Patient In Tables E6, E7 and E8 are displayed clinical characteristics of the treated tooth, including tooth type, and tooth arch. Figure D7 shows that most stepwise excavation procedures were accomplished on molars (52%), while 29% were accomplished on premolars, 11% on incisors and the least on canines (8%). Also, 55% of procedures were completed on maxillary teeth, and 45% completed on mandibular teeth (Figure D8). The distribution of the number of surfaces in the treated tooth was also of interest; however, this information was not available for all years. The number of restored surfaces was available for only two teeth treated in 2004, none of the teeth treated in 2005 through 2007,100 of the 188 teeth treated in 2008, and all teeth treated in The data showed that the number of surfaces was consistently reported on SWPs starting on July 7 th, The number of surfaces involved on the SWP of the first appointment were divided into 5 groups: one (22%), two (44%), three (23%), four (8%) and five surfaces (3%) as shown in Figure D9. According to these findings, the most common amount of surfaces treated after first SWP appointment was 2. Frequency distribution for number of surfaces is displayed on Table E8. Regarding the type of provider that performed the first appointment of the SWP, 85% of the studied procedures were performed at the pre-doctoral level, 5%

84 69 corresponded to graduate level and 10% were completed by faculty (Figure D10). It is clear that most procedures are performed by a pre-doctoral provider is expected based on the setting where this retrospective study is performed and possible the type of patient pool in the pre-doctoral clinic. Frequency distribution for number of surfaces is displayed on Table E5. All of the figures are based upon the first SWP of the patient done at the UICOD during the period Basic descriptors for patients divided by Re-entry status Figure 8 (below) shows that the distribution for age is weighted toward younger ages. For the number of miles to the UICOD, the mean was 76.8 miles, with a standard deviation of 185 and a median of 41.5 miles. Figure 9, displayed below, shows the distribution for miles traveled for all patients demonstrating a predominance of patients in the group that traveled less than 100 miles. Figure 8. Distribution of patients that had re-evaluation/re-entry appointment by age group (Y axis shows fraction per year).

85 70 Figure 9. Distribution for miles to UICOD for all patients that had re-evaluation/re-entry appointment (Y axis shows fraction per mile). Figure 10. Distribution of miles for patients that had re-evaluation/re-entry appointment and traveled less than 500 miles (Y axis shows fraction per mile).

86 71 Figure 10 shows the distribution of the miles traveled for less than 500 miles where we see the largest portion traveling within 20 miles, which correspond to people living in the Iowa City and closer surroundings (e.g., Cedar Rapids is excluded on this range). For the number of month s re-entry appointment interval the mean was 194 days (approx. 6 months) with standard deviation of days and median of 190 days. Figure 11 shows the distribution of days (months) until re-entry interval appointment. This histogram shows two large groups, less than 50 days, and in the middle between 150 and 250 days, similarly to what was shown previously. Figure 11. Distribution of days (months) until re-entry interval appointment (Y axis shows fraction per day). Of the 1,326 unique patients/ procedures, 608 had re-entry at some point in time and 518 had re-entry within 18 months after the 1 st appointment (Table E13). Table E14 shows the descriptive statistics of quantitative covariates for the 518 patients having reentry appointment within 18 months. For patients with re-entry, mean age was 38 years

87 72 (range years), with the standard deviation of 13.9 and median equal to 35.3 years. Further comparison of descriptive statistics between re-entry and no re-entry status can be made using data from the bivariate analysis section (Table E38 and E39). Table E15, presents the frequency distribution for gender. This shows 51.2% (265) female and 48.7 % (252) male that had re-entry. The table also shows those patients that did not have re-entry, 53.5% (432) female and 46.5% (376) male. Table E16 displays the frequency distribution for the patient that had a SWP re-entry and had dental insurance. This table shows that of 518 patients that had re-entry appointment, 40.7 % (211) had dental insurance and 59.3% (307) did not have any type of dental insurance. For the patients that did not have a SWP re-entry, 34.5% (279) had dental insurance and 65.5% (529) did not have any type of dental insurance. Table E17 presents the frequency distribution for the patients that had a SWP re-entry and were self-pay. Of the 518 patients that had re-entry appointment, 47.7% (247) were self-pay and 52.3% (271) had some type of insurance. Table E18 presents the frequency distribution for the patients that had a SWP re-entry and were Medicaid. Of the 518 patients that had re-entry appointment 11.6% (60) were Medicaid and 88.4% (458) were not. Table E19 displays the frequency distribution for the patient that had a SWP reentry and a sedative filling was placed as a final restoration. Of the 518 patients that had re-evaluation/ re-entry appointment 8.3% (43) had a sedative filling placed. A similar percentage is found to that shown in the previous sections, which was 11% (14% out of the direct/indirect restorations, which was 78% out of the total). Table E20 shows that of the 518 patients that had re-evaluation/ re-entry appointment 3.5% (18) had a glass ionomer placed. Table E21 presents the frequency distribution for the patient that had a SWP re-entry and an amalgam restoration was placed as the final restoration. Of the 518 patients that had SWP re-evaluation/ re-entry appointment 32.6% (169) had an amalgam placed as the final restoration, which is similar to the 30% found for all procedures. Table E22 shows the frequency distribution for the patient that had a SWP re-entry and a resin

88 73 composite was placed as final restoration. This table presents that of the 518 patients that had re-entry appointment 23.2% (120) had a resin composite placed (27% for the previous section). Table E23 displays the frequency distribution for the patient that had a SWP re-evaluation/ re-entry and an onlay was placed as a final restoration. Of the 518 patients that had re-entry appointment 0.97% (5) had an onlay placed as a final restoration (0.78% for all procedures). Table E24 shows that of the 518 patients that had a SWP re-evaluation/re-entry appointment 6.1% (32) had a crown placed as the final restoration over a vital tooth. Of the 518 patients having a re-evaluation/re-entry appointment 74.7% (387) were successful stepwise excavation treatments, similar to the 78% reported previously. Table E25 presents the frequency distribution for patients that had a SWP reevaluation/ re-entry appointment but the tooth ended up needing a root canal treatment (RCT). Of the 518 patients that had a re-evaluation/re-entry appointment, 14.1% (73) ended up having a RCT. Table E26 presents the frequency distribution for the patient that had a SWP re-evaluation/ re-entry appointment and a tooth extraction as the final outcome (TE). Of the 518 patients that had a re-entry appointment, 10.8% (56) ended up being extracted. Table E27 presents the frequency distribution for patients that had a SWP re-evaluation/ re-entry appointment and ended up with an implant as final outcome showing a small percentage (0.39%). Therefore, of the 518 patients having a re-entry, 25.3 % (131) ended up having a RCT or TE. In summary, there are not significant changes from that shown in the analysis considering all procedures. Bivariate Analyses Results are based upon the re-entry outcome status, defined in terms of whether or not there was completion of re-evaluation/re-entry within 18 months of the stepwise excavation procedure; analyses were done using only one SWP per patient. The SWP

89 74 used was the first performed for that patient at the UI College of Dentistry during the study period, The variable STATUS represents this outcome in the following displays. Bivariate relationships of categorical covariates with this outcome were assessed using chi-square tests of association. The association between each quantitative variable with the re-entry status was assessed using the Wilcoxon Rank Sum test for all quantitative variables and descriptive statistics for all variables and box plots for the age variable were generated for each re-entry status. Bivariate Analyses involving Categorical Covariates Analysis of the data using chi-square tests of association provided no evidence of bivariate association between the primary outcome (re-entry status at 18 months post- SWP) and either gender (χ2 = 0.62; df=1; p=0.43), or tooth arch (χ2 = 0.37; df=1; p=0.55). Because of the large number of categories (32), the chi-square approximation was not valid for consideration of potential associations with the specific site (tooth number); however, there was no suggestion of an association between tooth number and the re-entry status (approximate p-value of 0.20). The contingency tables (Table E28 and E29) associated with the above analyses show the similarity of re-entry rates for these subgroups. The data provided evidence of association between the primary outcome and each of the following: dental insurance status (χ2 = 11.00; df=2; p=0.0041), provider level (χ2 = 26.17; df=2; p<0.0001), and tooth type (χ2 = 20.30; df=3; p=0.0001). Table E30, E31 and E32 are the contingency tables associated with the above analyses. As indicated in the table E30, SWPs of patients with dental insurance were most likely to result in reentry within 18 months, while those of patients with Medicaid were least likely. The reentry rates for SWPs performed by faculty or residents were similar (Table E31), whereas those for SWPs performed by undergraduate operators were lower. SWPs performed on

90 75 molar and premolar teeth were more likely to result in re-entry than those performed on canines or incisors (Table E32). Bivariate Analyses involving Quantitative Covariates Evidence was also found of an association between the primary outcome (re-entry status) and the calendar year in which the SWP was done (χ2 = 21.52; df=8; p=0.0059), treating calendar year as a nominal outcome. Analyses were also carried out based upon the Wilcoxon Rank Sum test, which provided evidence of a trend over secular time (p = ), indicating that SWPs performed earlier in the study period were more likely to result in completed re-evaluation/re-entry within 18 months after the SWP was performed. This is illustrated in the Table E33. Similarly, evidence was also found of an association between the primary outcome and the number of surfaces in the treated tooth (χ2 = 10.82; df=8; p=0.029), treating this covariate as a nominal outcome (Table E34). Analyses were also carried out based upon the Wilcoxon Rank Sum test, which took into account the quantitative nature of the covariate. However, there was no evidence that the distribution of the number of total surfaces in the treated tooth differed between those who did and did complete reentry within 18 months (p=0.99), based on the Wilcoxon test, providing no evidence for an increasing or decreasing trend in re-entry rates based on the number of surfaces. The pattern, which shows no systematic trend, is illustrated in the table 58, Appendix E. It must be noted that this information was not available for approximately 45% of the SWPs, since systematic collection of this information did not commence until sometime in Wilcoxon Rank Sum tests were used to assess whether the distribution of age and driving distance to the UICOD differed based on re-entry status. Relationships with reentry status were also assessed for the number of recall examinations and prophy visits in

91 76 the 18 months prior to the SWP ( Table E35) and the total number of restorations at the UICOD in the 18 months prior to the SWP ( Table E37). The data provided evidence that the distribution of age differed significantly (Wilcoxon Rank Sum test; p < ) by re-entry status: patients with completed reentry and re-evaluation status tended to be older than those without re-entry within 18 months. The median age of those completing re-entry was 38.1 years; that of those not completing re-entry within 18 months was 34.2 years (Tables E38 and E39). A box plot illustrating the distribution of age within the two groups defined by reentry status is given in Figure E4. This graph shows that the older patients are more likely to return than younger ones. The data provided evidence that re-entry status differed in the distribution of the number of recall examinations and prophy visits ( categorized as 0,1,2 and 3+) in the 18 months prior to the SWP (Wilcoxon Rank Sum test; p < ): patients with completed re-entry and re-evaluation status tended to have more such visits than those without reentry within 18 months. However, it should be noted that the number of such visits was quite low in most patients the median number of visits was zero in both subgroups based on recall status (Tables E38 and E39). This is illustrated in the Table E35, which categorizes the number of recall/prophy visits. This tabulation shows that more than half of the patient in each group had no such visits (67.95% of those with no re-entry and 57.34% of those with re-entry) fewer in the re-entry group but also that more patients with re-entry had three or more such visits (13.51%) compared to those patients who did not completed re-entry within 18 months, 5.20% of whom had three or more recall/prophy visits in the 18 months prior to the relevant SWP. There was no evidence that the distribution of driving distances (categorized as <35, and >100 miles) differed between those who did and did complete re-entry within 18 months (Wilcoxon Rank Sum test; p=0.25). The median distance was 41.5 miles for those who completed re-entry and 44.8 miles for those who did not (Tables E38

92 77 and E39). The similarity between the two outcome groups is also seen in the categorization shown in Table E36. There was no evidence that those who did and did not complete re-evaluation/reentry within 18 months differed in the distribution of the total number of restorations (categorized as: 0, 1, 2, 3+) at the UICOD in the 18 months prior to the SWP (Wilcoxon Rank Sum test; p = 0.22). The similarity between the two outcome groups is seen in the categorization shown in Table E37; note that in both groups, more than half of the patients had only a single visit of this type in the 18 months prior to the performance of the SWP. Descriptive statistics are also given in separate tables (Table E38 and E39) for all quantitative measures evaluated using the Wilcoxon Rank Sum procedure; these are reported separately for those who did and did not complete re-evaluation/re-entry within 18 months of the performance of the stepwise excavation procedure. Logistic Regression Modeling of Re-entry Status Multiple logistic regression modeling was used to model the factors significantly associated with the probability of re-entry status. Explanatory variables considered included: gender ( male and female), age (18-29, 30-41,42-53 and 54 to 65 years) and insurance status of the patient (dental insurance, self-pay and Medicaid), driving distance to the UICOD ( 0-35 miles, miles and >100 miles), provider level (faculty, resident, or undergraduate), the tooth type (incisors, canine, premolar and molars) and arch ( maxillary and mandibular) of the SWP, the number of recall or prophy visits ( 0,1, 2 and 3 or more) in the 18 months prior to the performance of the SWP, the number of restorations at the UI COD (0,1, 2 and 3 or more) in the 18 months prior to the SWP, and the year in which the SWP was performed. Alternative model selection methods, including forward, backward and stepwise selection procedures were completed and each resulted in the same final model. This

93 78 model included five covariates: tooth type (canine, incisor, molar, or premolar), provider level (faculty, resident, or undergraduate), the year the SWP was performed, patient age (18-29, 30-41, and 54 to 65 years) and the number of recall or prophy visits (0, 1, 2 and 3 or more) in the 18 months prior to the performance of the SWP. Alternative models were fit using both nominal categorical and quantitative expressions of patient age, calendar year of SWP and the number of recall/prophy visits in the 18 months prior to the SWP; in the latter case, an ordinal outcome (0, 1, 2, 3+ recall/prophy visits) was also considered. In all three instances, the quantitative expression of the variable provided the best model fit based upon Akaike s information criteria, and so the recorded quantitative values for these three covariates were used in the final model. All first-order interactions (interactions between all possible pairs of covariates) were considered, and none were found to be significant. There was no evidence of lack of fit, based upon the Hosmer and Lemeshow goodness of fit statistic (p=0.41). The significance probabilities for these five significant covariates are given in Tables E40 to E42, followed by the maximum likelihood estimates of the parameter estimates from the logistic regression model, and the estimates of the odds ratios from logistic modeling, with the associated 95% confidence intervals. These findings are summarized in Table E43. The following results refer to adjusted estimates and p-values, i.e., they address the effect of a particular covariate after adjustment for the effects of the other covariates in the model. All five factors are seen to be highly significant. As indicated by these results, the older the patient, the more likely the patient was to return for re-evaluation/re-entry of the SWP within 18 months (p < ). SWPs performed early in the study period of were more likely to result in such re-entry than were SWPs performed later in the study period (p = ). The more recall/prophy visits at the UI COD in the 18-month

94 79 period prior to the SWP, the more likely that re-entry would be completed within 18 months (p < ). The probability of re-entry was also significantly related to provider level (p = ). When the faculty member was the provider, the SWP was significantly (p = ) more likely to result in re-entry within 18 months than if the provider was an undergraduate (OR = 1.93; 95% CI: ). While the estimated probability of reentry was greater when the provider was faculty than when the provider was a resident, it was not significantly greater (OR = 1.18; 95% CI: ; p=0.60), nor was the reentry rate significantly greater for resident providers than for undergraduate providers (OR = 1.64; 95% CI: ), although the results for this comparison were quite suggestive (p=0.0542). The type of tooth for which the SWP was performed (canine, incisor, molar or premolar) was also related to the primary outcome of re-entry within 18 months (p < ), again after adjustment for the other four covariates. Generally speaking, the probability of re-entry was greatest if the SWP was performed on a molar tooth, with quite similar results for premolar teeth (OR = 1.02; 95% CI: ; p=0.87 for comparison of molars vs. premolars). The next lowest rates of re-entry was for SWPs performed on canines, with the lowest probability of re-entry when the SWP was performed on an incisor; however, the odds ratio comparing re-entry for canines vs. incisors was not significant (OR = 1.43; 95% CI: ; p=0.24). Re-entry was significantly more likely for molar teeth than for either canines (OR = 1.75; 95% CI: ; p=0.0165) or for incisors (OR = 2.49; 95% CI: ; p < Similarly, re-entry was significantly more likely for premolar teeth than for either canines (OR = 1.72; 95% CI: ; p=0.0267) or for incisors (OR = 2.43; 95% CI: ; p < These relationships are illustrated in the schedule of predicted probabilities of re-entry based upon the logistic model given in Figure E5. This heat map shows predicted probabilities of re-entry based upon multiple logistic models for

95 80 selected values of covariates and is provided in two versions. Color variation is used to convey patterns of low to high probability of re-entry with the gradient applied across all table entries. The dark green shows high probability of re-entry and the dark red indicates low probability of re-entry. These predicted probabilities were calculated for a subset of possible values for purposes of illustration. While all combinations of tooth type and provider level are represented, calculations were made for ages 25, 30, 45 and 60; for treatment years 2004, 2008 and 2012, and for two values of the number of recall/prophy visits in the 18 months prior to performance of the SWP (0 and 3 such visits). The impact of patient age, provider level, and tooth type are further illustrated in Figures E6 and E7. In these figures, the values of two covariates are held constant: the year of treatment is fixed at 2008, which is the midpoint of the interval as well as the median year of treatment, whereas the number of recall/prophy visits in the 18 months prior to performance of the SWP was set to zero, since 63% of SWPs were associated with that value. Figure E6 shows the relationship between age and the predicted probability of reentry within 18 months derived from logistic modeling for each of the four tooth types, with bottom, center and bottom panels giving the probabilities associated with faculty, resident or undergraduate providers, respectively. The similarity between re-entry rates for SWPs performed on molars and premolars is particularly apparent. Figure E7 shows the relationship between age and the predicted probability of reentry within 18 months derived from logistic modeling for each of the provider levels, with panels in clockwise order from the top-left panel giving the probabilities associated with molars, premolars, incisors and canines. The highest re-entry rates are for SWPs performed by faculty and the lowest for those performed by undergraduate providers. Values for residents are intermediate, but tend to be more similar to those for faculty.

96 81 Despite the significance of the bivariate association between completed re-entry in 18 months and insurance status (χ2 = 11.00; df=2; p=0.0041), the covariate insurance status was not retained in the multiple logistic regression model. Insurance status was highly correlated with provider level (χ2 = 94.77; df=4; p<0.0001). As can be seen in the Table E44, more patients with dental insurance were treated by faculty than would have been expected if insurance status were independent of provider status, whereas more patients with Self Pay or Medicaid status were treated by undergraduates than expected under independence. Clinical outcomes Clinical outcomes using one SWP per patient Out of 1,326 patients 60.9% (808) did not have re-entry within 18 months. A schematic showing the outcomes for these 1,326 patients/swps are provided in Figure 12, which indicates that 518 (39.1%) returned to the UI College of Dentistry (UICOD) for re-evaluation and re-entry within 18 months of the performance of the stepwise excavation procedure. Among the remaining 808 (60.9%), where re-evaluation/re-entry was not completed, the patient did not return to the UICOD in 228 instances (28.2%); in the remaining 580 instances (71.8%), the patient returned to the UICOD, but the tooth was not re-evaluated as displayed below in Figure 12. Among the 518 SWPs where reevaluation/re-entry was completed, 387 (74.7%) resulted in direct or indirect restoration avoiding RCT and TE while 131 (25.3%) resulted in root canal treatment or tooth extraction. The 18- month clinical outcomes of these 518 SWPs were distributed as follows: 169 amalgams (32.6%), 32 crowns (6.2%), 5 onlay/inlay (1.0%), 120 resin composite restorations (23.2%), 18 glass ionomer restorations (3.5%) and 43 sedative fillings (8.3%), all of which are considered to be clinical successes, and 73 (14.1%) root canal treatments and 58 (11.2%) tooth extractions, which are considered to represent clinical failures (Figure 12).

97 82 Figure 12. Diagram flowchart of stepwise excavation procedure outcome when considering the first procedure per patient only. Main Finding The major finding for this study was that most of the stepwise excavation procedures performed at The University of Iowa College of Dentistry, between 2004 and

98 were not re-evaluated and re-entered, which is in discrepancy to our main expected finding. Specific Findings 1. The results showed that the proportion of teeth with stepwise procedures that were never reevaluated was higher than the teeth that were re-evaluated. This finding responds our first specific expected finding described at the material and methods section. 2. The results showed that the median for the number of month s appointment or reentry interval was 190 days (approx. 6 months). Also, the majority of procedures were re-evaluated/re-entered between 5 to 9 months (39%). This is in agreement to the second specific expected finding. 3. Results of this study showed that only 30% of the total teeth treated with stepwise excavation procedure were restored with a direct restorative procedure such as amalgam, direct resin composite, glass ionomer, sedative filling or an indirect restoration, such as crown or inlays/onlays. This is in disagreement with our third specific expected finding described at the material and methods section. General Objectives 1. The proportion of procedures procedure that were re-evaluated and re-entered at the University of Iowa College of Dentistry (UICOD) from January 2004 to December 2012 was 39%. 2. The results showed strong association between the re-entry status and the following demographic variables: dental insurance status, age and number of recalls. 3. The results showed strong association between the re-entry status and the following tooth characteristics: provider level, tooth type, and the calendar year in which the SWP was done.

99 84 Specific Objectives 1. The percentage of teeth treated with stepwise excavation procedure that had a reentry appointments/procedure was 39%. 2. The percentage of teeth that had stepwise excavation procedure and were never reevaluated was 61%. 3. The data provided evidence of association between patient age and re-entry status at 18 months post-swp. 4. The data provided no evidence of association between gender and re-entry status at 18 months post-swp. 5. The data provided evidence of association between the provider level and re-entry status at 18 months post-swp. 6. The data provided evidence of association between re-entry status at 18 months post SWP and the number of tooth surfaces restored treating this covariate as a nominal outcome. However, there was no evidence of association between of the number of surfaces and re-entry status at 18 months post-swp based on the quantitative test. 7. The data provided evidence of association between different tooth type (central incisor, lateral incisor, canine, molars or premolars) and re-entry status at 18 months post-swp. 8. The data provided no evidence of association between tooth arch (maxillary or mandibular) and re-entry status at 18 months post-swp. 9. The data provided evidence of association between total number of recall exams before SWP was completed and re-entry status at 18 months post-swp. 10. The data provided no evidence of association between number of miles that patient traveled to the UICOD and re-entry status at 18 months post-swp. 11. The data provided evidence of association between the type of dental insurance of the patient at the time of the SWP and re-entry status at 18 months post-swp.

100 Among the 518 SWPs where re-evaluation/re-entry was completed. Of these 518 SWPs, 75% (387) had a final direct/indirect restorative material placed. A total of 169 restorations were amalgams (32.6%), 32 crowns (6.2%), 5 onlay/inlay (1.0%), 120 resin composite restorations (23.2%), 18 glass ionomer restorations (3.5%) and 43 sedative fillings (8.3%). And 73 (14.1%) root canal treatments and 58 (11.2%) tooth extractions. Summary of results In the present study, a total 1985 of stepwise excavation caries removal procedures were performed in 1326 patients at the UICOD between 2004 and To perform the associations between variables one procedure per patient was selected to have independent observations. Then, within the 18-months frame of time 1326 patients were analyzed. Of these 1326 patients, 608 had re-entry with 518 patients having re-entry within 18 months. Of these 1326 procedures, the number of teeth reevaluated/re-entered was 518 (39%) within 18 months after the first appointment. Likewise, the number of teeth that were not re-entered/re-evaluated after stepwise excavation procedure was completed was 808 (61%), which provides valuable information regarding to patient compliance or absenteeism during the second re-evaluation /re-entry appointment. The results showed strong association between the re-entry status and the dental insurance status, provider level, tooth type, age, number of recalls and the calendar year in which the SWP was done. Also, the present study presented evidence that the distribution of age differed significantly by re-entry status. Logistic regression modeling revealed that five factors were seen to be highly significant: provider level (faculty, resident, or undergraduate), tooth type (canine, incisor, molar, or premolar), the number of recall or prophy visits in the 18 months prior to the performance of the SWP, the year the SWP was performed and patient age.

101 86 Additionally, the present study revealed on the clinical outcomes of stepwise excavation procedure that 518 patients having a re-entry appointment 75% (387) resulted in a direct or indirect restorative outcome. Of the 518 patients having a re-entry, 25.3 % (131) ended up in a RCT or TE.

102 87 CHAPTER V DISCUSSION Background information The main purpose of this study was to assess the proportion of patients that had their 1 st SWP re-evaluated and re-entered and to evaluate the association between patient demographics factors, tooth specific variables and re-entry status and whether reevaluation occurred. Main findings The present study revealed that, from a total of 1326 stepwise excavation procedures performed at UICOD between July 2004 and December 2012, 39 % (518) had their re-entry/re-evaluation completed when procedures were followed up to 18 months. On the other hand, from the 1326 total procedures completed, 61% (808) were not reevaluated in this same 18 month period. This occurred either because the patient did not come back to the UICOD (29%) or the treated tooth was not addressed when patient came back to the UICOD (72%). These results do not sustain the main expected finding which is that most stepwise excavation procedures accomplished at the UICOD between 2004 and 2012 were re-evaluated and re-entered. The lack of follow-up was not totally un-expected given that the loss of patients is a common problem in most stepwise excavation studies (E.Kidd, 2004). This high percentage of patients lost to follow-up has also been described in a recent study (Maltz et al., 2012a). This problem is also to be expected in a dental school where the patient population is fairly transient and there is typically a fairly high turnover of patients. Other possible reasons might include: low patient compliance, which has already been reported in the literature related to high caries risk patients (Guzmán-Armstrong and Warren, 2007); patients switching to another dental health provider, or the interim restoration placed on the SWP treated tooth provided adequate esthetics and function. Moreover, possibly some of these teeth being treated were asymptomatic, and from the patient s

103 88 point of view, there was no need to return if there was no discomfort associated with the tooth. With the lack of follow-up of SWP the evidence needs to be evaluated for other approaches to treat deep carious lesions. This view is supported by recent literature, such as Bjorndal (2010), who suggested that the re-entry step may not be needed after partial caries removal when treating deep carious lesions. This proposed treatment approach is based on a randomized clinical trial (Maltz et al., 2012b) which reported a high incidence of stepwise excavation cases that did not receive the re-entry treatment as planned in the protocol because the patients did not return, similar to the present study. However, additional research is required to draw definite conclusions about the effectiveness of non-stepwise excavation and stepwise excavation procedures on the treatment of deep carious lesions. The second major finding of this study was that logistic regression modeling revealed strong association between the re-entry status provider level (p=0.0009), tooth type (p<0.0001), number of recalls exams before the SWP (p<0.0001), treatment year (p=0.0004), and age of the patient at the time that SWP was performed (p<0.0001). Although dental insurance was not included in the final logistic regression model, it was shown to be highly associated to provider level, thus is also correlated with the re-entry status, as shown by the bivariate analysis. To our knowledge, there are no studies reporting similar associations between patient characteristics and tooth characteristics with completion of re-evaluation of the stepwise excavation procedure. Therefore, the present study provided important information that age, provider level, tooth type, number of recalls, dental insurance and treatment year are significant factors affecting the probability of re-evaluation/re-entry of a stepwise excavation procedure. The present study also provides additional evidence with respect to clinical outcomes of stepwise excavation procedure at UICOD during 2004 to From the 1326 total procedures completed between 2004 and 2102 approximately 75% (387) of

104 89 these 518 stepwise procedures were re-evaluated and restored without a root canal treatment. The other 25% (131) were re-evaluated/ re-entered but resulted in a root canal treatment or tooth extraction outcome. So, even though a low percentage of patients came back for the re-entry, among those that did return most resulted in a successful clinical outcome (they were restored with a direct or indirect restorative material and did not result in a clinical outcome of root canal treatment or tooth extraction). Two of the most recent stepwise excavation studies (Maltz et. al., (2012b), BjørndaL et. al., 2010) have shown an 86% and 74.1% treatment success respectively, which is similar to what is reported in the present study. Maltz et al., (2012b) reported a high success rate (86%) after 18 months of SWP. However, in the Maltz et al. study, (2012b) the teeth that were found with active lesions in the re-entry appointment of SW group were restored with a temporary material and the caries tissue was removed in a third appointment, which may explain the higher success rate for SWP compared to other studies. Bjørndal et al., (2010) reported a success rate for stepwise excavation of 74.1% vs. 62.4% for complete caries excavation after 1 year of follow-up. Nevertheless, the cited studies were randomized clinical trials and their main outcome was pulp vitality and absence of periapical lesions which differs from the final outcomes presented here. Thus, although these results are useful as references, a direct comparison cannot be made to the present study. An interesting finding in this study was that there were cases where the sedative filling (temporary filling) was kept and no permanent restoration was completed. Eight percent (43) of the re-entered final restorations were sedative fillings which were not removed within the 18 months period that teeth were assessed. This percentage of sedative fillings was an unexpected finding in the present study since these interim restorations are intended to be a temporary material for patients and not a permanent restoration. A strong point of this study is that these teeth were re-evaluated and considered as succesful stepwise excavation clinical outcomes but removal of temporary restoration was not completed. These treatments might be considered as one-step

105 90 incomplete caries removal. This finding is in agreement with clinical trials that suggest that re-opening the cavity to remove remaining dentin carious tissue might not always be necessary (Maltz et al., 2012a and 2012b). Most stepwise excavation procedures were accomplished on molars (52%) while 11% o were accomplished on incisors (11%) and the least on canines (8%). This higher percentage of procedures accomplished on molars compared to canine and incisors was expected due to the extent of interproximal carious lesions that might not be visible from the occlusal surface and may not be detected early (Pretty 2006). Another interesting finding of this study is that most stepwise excavation procedures were performed by pre-doctoral level clinicians (85%). Despite the fact that the present study was developed in a dental school setting, this finding is in agreement with the results of Weber et al., (2011) who reported that younger dentists were inclined to complete more conservative caries removal approaches, such as stepwise excavation treatment, compared with those indicated by older dentists. Weber et al., (2011) concluded that the year of college graduation influenced treatment decisions and that younger dentists preferred treatments based on the most recent scientific evidence regarding caries excavation. However, according to the results of this study a stepwise excavation procedure performed by a student was less likely to have a re-entry. Another variable explored in the present study was the re-entry appointment interval. In our study, the time between first and second appointment was highly variable. Among the 1,326 patients, 518 of them returned to complete re-evaluation/re-entry within 18 months. The length of time to re-entry varied from 0.03 to months, with a mean time to re-entry of 6.4 months, and a median time to re-entry of 6.25 months. This might be related to the fact that patients received a reminder card at 6 months as part of the stepwise excavation procedure guidelines at UICOD. The length of time to re-entry found in the present study is concordant with the Bjorndal and Thylstrup, (1998) study where the final excavation was completed after a treatment interval ranging from 2 to 19

106 91 months, with a median of 6 months. Likewise, Ricketts el at., (2013) found that in the stepwise excavation studies, the time interval between first stage excavation and re-entry varied between 4 and 24 weeks. On the other hand, Bjorndal et. al., (2010) reported to have significantly higher success rate for stepwise excavation treatment (74.1%) with 8 12 weeks for treatment interval compared with direct complete excavation of deep carious lesions. The authors explained that they used the shorter interval time since there was no scientific evidence that a prolonged treatment interval might have resulted in higher success. Likewise, Leksell et al. (1996) found no difference in the frequency of pulp exposure between a group of patients treated within a shorter time interval (8 to10 weeks) and one treated within a longer time interval (11 to 24 weeks). This is also in agreement with Schwendicke et al. (2013) who suggested that it is not well-defined whether longer intervals between first and second visits could reduce the risks of pulpal exposure and complications. Schwendicke et al., (2013) also concluded that in most studies follow-up times varied considerably which might influence pulpal symptoms and restoration failures outcomes. Even though the main purpose of this study was to report the proportion of patients with completion of re-evaluation/re-entry over an 18 month interval, by assessing the findings about time to re-entry, it became clear that it would also be important to evaluate the association of the re-entry appointment interval and successful SWP treatment outcomes in future research. Previous studies suggest that the success outcome might not be affected by the length of the treatment interval (Leksell et al., 1996; Bjorndal et. al., 2010; Schwendicke et al., 2013). However, these studies may suggest that a possible solution to improve patient compliance is earlier re-evaluation within 8-12 weeks to increase the return rate of patients. This study showed that patients seen by faculty and residents had higher probability of re-entry. Some possible reasons might be that faculty required less time in performing procedures compared to cases where a student performed the treatment and the appointment took longer. This might cause dissatisfaction with the procedure being

107 92 performed by the student, and less willingness to return. Also, a higher socio-economic level associated with patient populations seen by faculty providers might be a reason for the association of a higher probability of re-entry. This could be explained as those with the highest socio economical level tends to be associated with higher educational levels and a greater number of preventive dental visits, so patients are more involved in treatment decisions (Marston, 1970). However, further investigation is strongly recommended to confirm this idea. The present study findings also suggest that the spread of knowledge should be more focused on the new generation of clinicians since they are more likely to apply these new methods in practice. The present study presented evidence that the distribution of age differed significantly (p < ) by re-entry status. According to our findings, older patients that had a SWP had a higher probability of re-entry. This difference could be explained by the assumption that older patients might be more responsible than younger ones and/or older patients place more importance on keeping their teeth. Also, older people who are retired have more open schedules increasing the availability of returning for re-entry. According to some studies, younger patients were less likely to follow their medical regimens than were older patients (Marston, 1970). A recent study about the German health care system utilization showed that the average number of visits increases with age (Janssen and Christian et al., 2014). This is consistent with the present study s finding where patients with completed re-entry and re-evaluation status tended to be older than those without reentry within 18 months. However, this finding is in contrast with Maltz et al. (2012a). In their randomized clinical trial a comparison was made between patient demographic variables (such as age, gender and geographical region) and tooth characteristics associated with teeth that were evaluated or not re-evaluated after partial caries removal and stepwise excavation procedures. However, their study did not find association between groups with respect to age (Maltz et al., 2012a). Furthermore, older patients that returned in the present study might have come back for some other issue and not for the

108 93 re-entry appointment; thus, it is still important to assess the outcome of these SWP that corresponds to older patients. In the present study most patients came from nearby or from medium distances (within 100 miles) to the dental school and distance were not found to be associated with whether the patients returned for re-entry. In a previous study, Maltz et al. (2012a) assessed the region where the patient came from but did not find significant association with the outcome, which is in agreement with the present results. The data also provided evidence that those who did and did not complete reevaluation/re-entry within 18 months differed in the distribution of the number of recall examinations and prophy visits in the 18 months prior to the SWP (p < ). Patients with completed re-entry and re-evaluation status tended to have more such visits than those without re-entry within 18 months. This association might be explained due to patients who regularly seek dental care are more compliant and may be more involved in their oral health care than patients that frequently miss appointments. The data showed evidence of an association between the re-entry status and the tooth type (p=0.0001). According to the results, molars and pre-molars had higher probability of re-entry. This finding could be explained since the temporary restorations on molars and premolars could present more occlusal wear compared to the restorations on canine and incisors, resulting in the need to return for a definitive restoration on molars and pre-molars. However, more investigation is needed to know if a higher percentage of these teeth that returned for re- evaluation returned for a definitive restoration or presented with other issues. Additionally, the present study showed evidence of an association between the re-entry status and the number of surfaces in the treated tooth when treated treating this covariate was used as a nominal outcome (p=0.029). However, when analyses were performed treating this variable as quantitative covariate, there was no evidence that the distribution of the number of total surfaces in the treated tooth differed between those

109 94 who did and did not complete re-entry within 18 months (p=0.99). The number of surfaces restored has been emphasized as one of the stronger indicator of treatment failure that might potentially lead to pulpal necrosis. In a randomized clinical trial, Maltz et al. (2012b), did not find differences between treatment groups evaluated and not evaluated with respect to the number of surfaces involved with the restoration (Maltz et al.,2012b) which is consistent with the present study s findings. However, more research is needed to produce conclusive findings about this issue. The data also provided evidence of association between completed re-entry in 18 months and the dental insurance status (p=0.0041), indicating that patients that had dental insurance were more likely to come back. Although logistic regression and bivariate analysis resulted in similar associations, dental insurance status and number of surfaces variables were not retained in the multiple logistic regression model of the re-entry status. The explanation of this is that these variables were highly associated with other variables which were included in the final logistic regression model. The Number of surfaces were associated with tooth type and dental insurance status was highly associated with provider level (p<0.0001). In the statistical analysis, more patients with dental insurance were treated by a faculty than would have been expected if dental insurance status were independent of provider status. An implication of this is the possibility that patients with dental insurance were more likely to go with faculty providers because of a higher socioeconomic status. On the other hand those without dental insurance may be looking for more affordable care and therefore work with student clinicians. However, this statement would be to speculate that a highest socio-economic level could be associated with the patient population seen by faculty providers. Therefore, it is strongly recommended that the association of these factors be investigated in future studies. The evidence from this study also suggests an association between re-entry status and the calendar year in which the SWP was completed (p=0.0059) indicating that SWPs performed earlier in the study period were more likely to result in completed re-

110 95 evaluation/re-entry within 18 months after the SWP was performed. Thus, patients treated in earlier years with a SWP had a higher probability of re-entry. This interesting finding might reflect that at the beginning of the implementation of the stepwise excavation program at the UICOD the information about SWP treatment protocol was more effectively disseminated. Then with time, new faculty, new residents and new students might have overlooked the SWP guidelines and the reinforcement to patients about the importance of the second appointment was not emphasized. This finding shows the importance of having continual training and seminars in dental schools to reinforce SWP clinical guidelines. Main Limitations Regarding the percentage of procedures that were restored after re-evaluation in the present study, an assumption in this study was that providers followed the UICOD stepwise excavation guidelines. This means that they properly identified deep carious lesions and did vitality tests on these teeth. Preliminary review of patient records showed that most procedures followed the stepwise excavation guidelines, and only three did not (they used other materials for temporary restoration). In order to overcome this limitation, a random review of SWP was completed to see if guidelines were followed. It was determined that in most of procedures guidelines were followed. A review of all procedures that resulted in a root canal treatment or tooth extraction was performed and the procedures where the protocol was not followed were excluded from this study. Another concern is with that the amount of carious dentin left in the cavity by the provider is unknown. Clinicians might have removed different amounts of carious dentin tissue in the second step or re-entry appointment. However this is a common point for all of stepwise excavation and partial caries removal studies and it is recognized to be challenging to differentiate clinically between infected and affected dentin as a measure of the amount of caries to remove. Schwendicke et al., (2013) reported that the

111 96 majority of studies reviewed revealed a high risk of bias since the randomization procedures were not appropriately described which could have caused operators to remove different amount of caries. Because of the subjective assessment, these clinicians could have removed different amounts of carious tissue. Also, questions about the amount of carious tissue to be removed or how much carious tissue should be left needs to be clarified (Schwendicke et. al., 2013). To solve these limitations we need more long term studies and clinical trials where the patient variables and procedures are more standardized. In the present study the number of restored surfaces was available for only two teeth treated in 2004, none of the teeth treated in 2005 through 2007,100 of the 188 teeth treated in 2008, and all teeth treated within Thus, the data showed that the number of surfaces was consistently reported on SWPs starting on July 7th, This represents a limitation for the data analysis however according to our findings, the most common amount of surfaces treated after the first SWP appointment was two which is in agreement with the findings of Maltz et al (2012b). Main Strengths The present study was the first long-term retrospective study reporting re-entry status of stepwise excavation procedures and association with demographics and tooth specific variables. A recent randomized clinical trial of partial vs. Stepwise excavation caries removal with a 3 year follow-up (Maltz et al., 2012a) presented a comparison between variables associated with treatments that were evaluated (213) and those that were lost to follow-up (86). The results of this randomized clinical trial (Maltz et al., 2012a) showed statistically significant differences in gender and number of surfaces restored, which is partially consistent with the present study since the present study did not find significant differences between groups with respect to gender but did find differences with respect to number of surfaces.

112 97 The present study provides additional evidence about the clinical outcomes of stepwise excavation procedures. This research showed that out of the 518 SWPs reevaluated 75% (387) were restored with a direct/indirect restoration which indicates a high percentage of successful treatment. The high percentage of amalgam (33%) and resin composite (23%) restorations was expected since amalgam and resin composite are both considered to be appropriate materials for direct fillings (Opdam et al., 2010). A strong point of the present study is that it considered that some patients had more than one SWP. From the 1,326 patients, 983 (74.1%) had only a single stepwise excavation procedure within the study period and the remaining 25.9% had from 2 to 12 procedures. in order to perform statistical analysis and to have independence between the study variables only one procedure per patient was selected. The SWP used was the first performed for that patient at the UI College of Dentistry during the study period, This process showed similarities with other studies, where an average of 1.8 and 2.5 procedures per patient were assessed (Magnusson et al., 1977 and Mertz-Fairhurst et al., 1998). Another important point of the present study was that in order to guarantee the internal validity of this study, a random review of 50 SWP per year from 2004 to 2012 was completed to determine if these cases followed the University of Iowa Clinical Guidelines for Stepwise Excavation Procedure. Also, the total number of SWP resulting in RCT (root canal treatment) or TE and (extraction) clinical outcomes were reviewed to verify if these were actually SWP. This study also analyzed demographic and tooth variables retrospectively without controlling for the variables as it would be done in a randomized clinical trial. This differs from existing prospective studies about stepwise excavation in the literature. For instance, Maltz et al. (2012b) compared the effectiveness of partial caries removal in one session and stepwise excavation (SW) in a randomized trial of 18 months of follow up. In this controlled clinical trial a high success rate for SW (86%) was reported. However,

113 98 as opposed to a retrospective study, in a clinical controlled study most patients are offered restorative motivations which might influence their decision to return for the reentry appointment. In a retrospective study like the one presented here, success outcomes are analyzed without any kind of patient incentive. In these procedures, patients that had a stepwise excavation procedure may return depending on their compliance or if they feel discomfort, which is a major consideration in the present study. Summary Results of this study showed a high percentage of procedures were not followed up or re-evaluated either because the patient did not come back (29%) or the treated tooth was not monitored (72%). This high percentage of patients that were not re-evaluated in this study was considered as an important finding, and may have been due to the lack of compliance by the patient or the need for a better follow-up system that should be reevaluated at the UICOD. However, for procedures that were re-evaluated a high percentage of positive outcomes (75%) were observed. In light of the results, it appears that stepwise excavation is an adequate treatment for deep carious lesions. These findings encourage practitioners to think about different approaches when faced with a deep carious lesion. Clinicians need to consider several factors in order to have success with the stepwise excavation caries removal procedure, such as patient s capability to come back, the patient s commitment to his/her treatment and an understanding of the treatment steps, age and the number of surfaces being treated. The results also provided evidence of association between the re-entry status and dental insurance status, provider level, tooth type, and the calendar year in in which the SWP was done. Thus the clinician should, in part, base treatment decisions not only on signs and symptoms but on patient-factors when they consider an incomplete caries removal procedure, such as stepwise excavation. That is clinicians need to practice a good case

114 99 selection. This statement agrees with a recent review study about the importance on case selection when performed a stepwise excavation procedure (Bjorndal et al 2013). This study, Bjorndal et al (2013) also reported that reentry may not be necessary after a SWP. However, additional research is needed to validate this statement, as well as more prospective studies such as randomized clinical trials and case control studies to demonstrate that a re-entry appointment is not required. Future directions These findings provide several insights for future research. First, additional investigation needs to assess the association between stepwise excavation clinical outcomes and the different patient demographic and tooth characteristics. Another important future direction relates to why there was a high loss of patients to follow-up. Low patient compliance was suggested as a possible reason, but it has also been related in the literature to high caries risk patients (Guzmán-Armstrong and Warren, 2007). The Guzmán-Armstrong and Warren (2007) study reported about the rampant caries patient program (RCCP) at The University of Iowa, where the authors described that of 71 patients that started the program about 50% dropped from the program due to possible economic concerns and/or lack of time and commitment. Patients presenting deep carious lesions, which appeared to extend to the dentin on radiographs, are immediately placed into the high-risk category because this is a well-documented predictor of future carious lesions (Featherstone et. al, 2007). However, the patient s caries risk was not a variable assessed in the present study. It would be of high importance to assess this variable in future research. This finding suggests that the high amount of procedures that were lost to follow-up might be related to the fact that the majority of patients were high caries risk patients. Another possible reason for the high loss of patients to follow-up could be that patients with asymptomatic teeth were not interested in returning for the second

115 100 appointment for a permanent restoration. A recent study, Schwendicke et al., (2013b) showed that one-step incomplete excavation had the highest probability of being costeffective compared to two-steps incomplete excavation (SWP) and complete excavation. Also, this study showed that two-step incomplete excavation (SWP) was found to be slightly less cost-effective than complete excavation (Schwendicke et al., 2013b). However, this study was performed in a simulation model, where the researchers simulated the treatment of a deep carious lesion on a molar tooth in a 15-year-old patient but not in a group of patients. Regarding this point, a retrospective study investigating long-term cost-effectiveness of the stepwise excavation procedure vs. complete caries removal would be valuable. Also, future studies that determine additional reasons for the high loss of patients to follow-up such as patient s health factors, patient understanding of recall appointments and financial factors would be interesting. It is likely that patients might not want to spend money for the permanent restoration as the stepwise excavation procedure fee does not include the cost of a permanent restoration that should be placed in the second appointment or re-entry. Further investigation might explore the survival of stepwise excavation treated teeth. As recent reviews have not identified the type of incomplete excavated teeth failure in detail, it is of high significance to investigate if there are any tooth specific characteristics and patient factors associated with risk of failure (Ricketts et al., 2013; S. Schwendicke et al., (2013b). This is consistent with Schwendicke et al.; (2013a) who pointed out that assessing long-term survival of restorations after incomplete caries removal procedure has high clinical importance. Also, it would be interesting to analyze the re-entry outcome status of stepwise excavation procedure in a database from another dental school. Bjorndal et al., (2010) performed a randomized clinical multicenter trial comparing stepwise excavation and complete caries removal: however there has been no retrospective multicenter study

116 101 comparing SW clinical outcomes. Thus, such study would be valuable in answering questions such as: Is there any difference in the proportion of patients re-evaluated between different dental schools? Do patients from different centers have the same compliance? Is there any difference in the proportion of successful outcome between different dental schools? This research would be a relevant step to our understanding of caries removal procedure outcomes in different academic settings. A frequent question in several studies is how much caries can remain in the cavity and how could this amount of carious tissue be quantified (E.Kidd 2004; Schwendicke et al., 2013a). There is also the possibility for investigation of materials used in incomplete caries removal, including bonding of restorative materials to carious dentin. Finally, it would be interesting to investigate if there is a direct association between the success of a stepwise excavation treatment and patient caries risk factors. These studies could provide essential guidance on how to make the most appropriate and patient-centered decisions when applying the stepwise excavation procedure.

117 102 CHAPTER VI CONCLUSION The main purpose of this study was to assess the proportion of patients that had a stepwise excavation procedure re-evaluated at The University of Iowa, College of Dentistry, between 2004 and This study also analyzed demographic factors and tooth specific characteristics and their association with the re-entry status of stepwise excavation caries removal procedures. The descriptive analysis of the information showed that of 1985 stepwise excavation procedures performed at UICOD between July 2004 and December 2012, 767 SWPs had their re-entry/re-evaluation completed when procedures were followed up to 18 months. From these, approximately 599 SWPs that had a final direct/indirect restorative material placed, which can be considered as an effective treatment. This sample included 1,326 unique patients / procedures. Of 1,326 patients, 808 did not have re-entry within 18 months and 518 had re-evaluation/re-entry within the 18 month time frame used in the analyses. Most procedures were completed on young patients; the mean age was 38 years. The majority of patients came from nearby and middle distances to The University of Iowa College of Dentistry were less than 500 miles. Regarding the number of month s reentry interval, the median time to re-entry was 6.25 months. Most patients did not have dental insurance at the first appointment. Also most procedures were performed by dental students (undergraduate students). Most stepwise excavation procedures were accomplished on molars and most final restorations were amalgams or resin composites. Regarding the number of surfaces involved with the restoration at the first appointment, most procedures had two surfaces restored. This study provided evidence of association between the re-entry status and the dental insurance status, provider level, tooth type, the calendar year in which the SWP

118 103 was done and the number of surfaces treated. Also, the present study presented evidence that the distribution of age differed significantly by re-entry status: since patients with completed re-entry and re-evaluation status tended to be older than those without re-entry within 18 months. The present study provided information that age, provider level, tooth type; number of recalls, dental insurance and treatment year are significant factors affecting the probability of re-evaluation/re-entry of a stepwise excavation procedure. These findings suggest that the stepwise excavation procedure may be indicated for the treatment of deep carious lesions treatment when patient factors are favorable to the outcome. The study provides important information on factors influencing the completion of re-evaluation, which could be used in clinical- decision making to approach SWP. As the present study is the first multi-year retrospective study evaluating the association between re-entry status and patient demographics and tooth characteristic variables, hopefully this research can serve as a base for future studies to evaluate the association between different variables and clinical treatment outcomes of stepwise excavation restorative procedures. In conclusion, study results suggest that treatment decisions for deep carious lesions should be based on patient factors and compliance characteristics, but these finding needs to be conformed in future studies. Further research should therefore concentrate on assessing the longevity and factors that influence success of the stepwise excavation caries removal procedures on additional populations. With such further research, clinicians might be able to have more patientoriented evidence to make the best treatment decision.

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124 109 Marston, M.V. "Compliance with medical regimens: A review of the literature." Nursing Research 19.4 (1970): Meyer-Lueckel, H. and Paris, S. eds. Caries Management-Science and Clinical Practice. Thieme (2013). Mertz-Fairhurst, E. J. "Ultraconservative and cariostatic sealed restorations: results at year 10." Journal of the American Dental Association (1998): Mickenautsch, S., Veerasamy Y., and Banerjee, A. "Pulp response to resinmodified glass ionomer and calcium hydroxide cements in deep cavities: a quantitative systematic review." Dental Materials 26.8 (2010): Mount, G. J. An atlas of glass-ionomer cements: a clinician's guide. Taylor & Francis (2004). Murray, P.E., Phillip J. L., and Smith, J. "Preserving the vital pulp in operative dentistry: 3. Thickness of remaining cavity dentine as a key mediator of pulpal injury and repair responses." Dental Update London 29.4 (2002): Murray, P. E., Windsor, L. J., Smyth, T. W., Hafez, A. A., and Cox, C. F. Analysis of pulpal reactions to restorative procedures, materials, pulp capping, and future therapies. Critical Reviews in Oral Biology & Medicine, 13.6 (2002): Nanci, A. Ten Cate's Oral Histology-Pageburst on VitalSource: Development, Structure, and Function. Elsevier Health Sciences (2007). Ngo, H. C., Mount, G., Mc Intyre, J., Tuisuva, J., & Von Doussa, R. J. Chemical exchange between glass-ionomer restorations and residual carious dentine in permanent molars: an in vivo study. Journal of dentistry 34.8 (2006): Oliveira, E.F., Carminatti, G,. Fontanella, V., Maltz, M. The monitoring of deep caries lesions after incomplete dentine caries removal: results after months. Clin Oral Investig 10.2 (2006): Opdam, N. J. M., Bronkhorst, E. M. Loomans, B. A. C. and Huysmans, M- CDNJM. "12-year survival of composite vs. amalgam restorations." Journal of Dental Research (2010): Orhan, A. I., Firdevs T. Oz, and Orhan, K. "Pulp exposure occurrence and outcomes after 1-or 2-visit indirect pulp therapy vs complete caries removal in primary and permanent molars." Pediatric dentistry 32.4 (2010). Petrie, A., J. S. Bulman, and Osborn, J.F."Further statistics in dentistry Part 6: Multiple linear regression." British dental journal (2002): Pretty, I.A. "Caries detection and diagnosis: novel technologies." Journal of dentistry (2006):

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127 112 APPENDIX A. INDEPENDENT VARIABLES Table A1. Demographics characteristics (Patient Specific Variables). Patient Specific Variables Variable Age Gender State City Zip Code Number of miles traveling to UICOD Type of dental insurance at the time of SW Total number of recall exam and prophy visits: 0-1, >1-2, >2 (18 months before/after SW procedure) Total # of patient appointments at UICOD (18 months before/after Independent Independent Independent Independent Independent Independent Independent Independent Independent SW procedure) 0-1, >1-2, >2 Total Number of restorations per patient at UICOD (18 months Independent before/after SW procedure) Initial Stepwise excavation date Re-entry Stepwise date Number of months Appointment re-entry interval Independent Independent Independent 0-3, >3-5, >5-7, >7-9, >9-11, >11

128 113 Table A2. Tooth specific study variables. Tooth specific variables Stepwise treated tooth number Tooth type (incisors, canine, premolar and molars) Tooth arch: maxillary, mandibular (%) Number of surfaces in SW treated tooth (1,2,3,4,5) Type of provider that performed stepwise procedure 1 st appointment pre-doctoral, graduate, Faculty Type of final restoration (glass ionomer, amalgam, resin composite, inlays/onlays, crowns) Number of surfaces of final restoration (1,2,3,4,5) Type of provider that performed final restoration ( pre-doctoral, graduate, Faculty) Variable Independent Independent Independent Independent Independent Independent Independent Independent

129 114 APPENDIX B. PROCEDURES CODES Table B1. ADA Procedures Codes of anterior Glass Ionomer restorations. Code Glass ionomer restorations, anterior D Surface Glass Ionomer, anterior D Surfaces Glass Ionomer, anterior D Surfaces Glass Ionomer, anterior D Surfaces Glass Ionomer, anterior Table B2. ADA Procedures Codes of posterior glass ionomer restorations. Code Glass ionomer restorations, posterior D Surface Glass Ionomer D Surfaces Glass Ionomer D Surfaces Glass Ionomer D Surfaces Glass Ionomer Table B3. ADA Procedures Codes amalgam restorations. Code Amalgam restorations D2140 D2150 D2160 D Surface Amalgam 2 Surface Amalgam 3 Surface Amalgam 4+ Surface Amalgam

130 115 Table B4. ADA Procedures Codes of anterior composite resin restorations. Code D2330 D2331 D2332 D2335 Composite resin restorations Anterior 1 Surface Composite, anterior 2 Surfaces Composite, anterior 3 Surfaces Composite, anterior 4+ Surface/involving incisal angle Table B5. ADA Procedures Codes of posterior composite resin restorations. Code D2391 D2392 D2393 D2394 Composite resin restorations, Posterior Resin-based composite - one surface Resin-based composite - two surfaces Resin-based composite - three surfaces Resin-based composite - four surfaces D Resin-based composite - five or more surfaces Table B6. ADA Procedures Codes of metallic INLAY/ONLAY restorations. Code D2510 D2520 D2530 D2543 D2544 Metallic inlay/onlay restorations 1 Surface Metallic Inlay 2 Surface Metallic Inlay 3+ Surface Metallic Inlay 3 Surface Metallic Onlay 4+ Surface Metallic Onlay

131 116 Table B7. ADA Procedures Codes of metallic restorations. Code D2410 D2420 Metallic restorations 1 Surface Gold Foil 2 Surface Gold FoiL Table B8. ADA Procedures of porcelain inlay/onlay restorations. Code D2610 D2620 D2630 D2642 D2643 D2644 Porcelain inlay/onlay restorations 1 Surface Porcelain Inlay 2 Surface Porcelain Inlay 3+ Surface Porcelain Inlay 2 Surface Porcelain Onlay 3 Surface Porcelain Onlay 4+ Surface Porcelain Onlay Table B9. ADA Procedures Codes resin inlay/onlay restorations. Code D2650 D2651 D2652 D2662 D2663 D2664 Resin inlay/onlay restorations 1 Surface Resin Inlay 2 Surface Resin Inlay 3+ Surface Resin Inlay 2 Surface Resin Onlay 3 Surface Resin Onlay 4+ Surface Resin Onlay

132 117 Table B10. ADA Procedures Codes of crowns-single restorations. Code D2710 D2740 D2750 D2751 D2752 D2780 D2790 D2791 D2792 Crown-single restorations only Crown-resin-based composite (indirect) Porcelain Jacket Porcelain fused to High Noble Metal Porcelain fused to Base Metal (Title XIX) Porcelain fused to Noble Metal 3/4 Cast High Noble Metal Full Cast High Noble Metal Full Cast Predominantly Base Metal (Title XIX) Full Cast Noble Metal Table B11. ADA Procedures Codes of Root canal therapy. Codes Root canal therapy D3310 Anterior D3320 Bicuspid D3330 Molar D Molar 4 Canals Table B12. ADA Procedures Codes of endodontic procedures. Code S3001 S3002 S3003 S3004 S3005 Endodontic procedures Open Chamber Extirpate pulp Medicate canal(s) Establish working length Prepare Canals

133 118 Table B13. ADA Procedures Codes of pulpotomy. Codes D3220 D3221 D3222 Pulpotomy Therapeutic Pulpotomy - primary and permanent Pulpal debridement - primary and permanent Partial pulpotomy for apexogenesis - permanent tooth Table B14. ADA Procedures Codes of extractions procedures. Code D7140 Tooth extractions Extraction, erupted tooth or exposed root (elevation &/or forceps removal) Table B15. Codes to determine Recall & Prophylaxis visit description. Codes D0120 Recall and prophylaxis visit description Periodic Oral Evaluation (Recall) D Collegiate Recall Exam (ADMS Clinic) S1001 S1002 S1003 S1004 S1005 D1110 Incomplete Scaling 1 quadrant Incomplete Scaling 2 quadrant Incomplete Scaling 3 quadrant Incomplete Scaling 4 quadrant Prophy completed Prophylaxis - adult D Prophylaxis - CRCL D Ultrasonic Scaling

134 119 APPENDIX C. IMPORTANT GUIDELINES FOR SWP Table C1. Clinical Guidelines for Stepwise Excavation Procedure of The University of Iowa College of Dentistry 1. Young patients with permanent teeth and young pulps may respond better. 2. Deep carious lesions at risk of accidental pulp exposure during caries removal (75% of dentin involved radiographically). 3. No symptoms of irreversible pulpitis such as spontaneous pain or provoked pulpal pain that lingers. 4. No swelling or marked tenderness to percussion which indicates pulp necrosis 5. Periapical radiograph with no evidence of perirradicular pathosis. 6. Vitality test (CO2 and EPT) to confirm vital pulp status. 7. Evaluate restorability of the tooth prior to performance of stepwise procedure. 8. Selection of a long-term temporary material as a transitional restoration that provides a good seal and avoids leakage. Fluoride release may be beneficial. (Fuji Triage or Fuji VII, Fuji IX, Fuji II LC)

135 120 APPENDIX D. SUMMARY DESCRIPTIVE ANALYSIS BY PATIENT Table D1. Summary table for descriptive statistics for demographic characteristics per patient. Demographics characteristics (Patient Specific Variables) Percent (n) Age 18 to 29 years 30 to 39 years 40 to 49 years 50 to 59 years 60 to 65 years 46 (611) 20 (263) 15 (204) 13 (172) 6 (76) Gender Male Female Unknown 47 (628) 53(697) 0.05 (1) Number of miles traveling to UICOD 0-35 miles miles >100 miles 45 (604) 42(554) 13 (168) Type of dental insurance at the time of stepwise excavation procedure Dental insurance No dental insurance Medicaid 37 (490) 48 (633) 15 (203)

136 121 Table D1. Continued Total number of recall exam and prophy visits (18 months prior to the SWP) Total Number of restorations per patient at UICOD (18months prior to the SWP) (846) 16 (207) 12 (161) 8 (112) 64 (844) 17 (225) 8 (114) 11 (143)

137 122 Table D2. Summary table of descriptive statistics for tooth specific variables per patient. Tooth characteristics Tooth type Incisors Canine Premolar Molars Tooth arch Maxillary Mandibular Number of surfaces restored in stepwise procedure first appointment (surfaces reported from July 7 th 2008 to 19 th December 2012) Percent (n) 11 (152) 8 (101) 29 (387) 52 (686) 55 (733) 45 (593) 22 (160) 44(320) 23(168) 8 (57) 3 (18) Type of provider that performed stepwise procedure first appointment Pre-doctoral Graduate Faculty Type of final restoration (from 387 stepwise excavation treated teeth) Sedative filling Glass ionomer Amalgam Resin composite Inlays-on lays Crown 85 (1123) 5 (72) 10 (131) 8 (43) 4 (18) 33 (169) 23 (120) 1 (5) 6 (32)

138 123 Age Age30 39 Age Age Age % 6% 15% 46% 20% Figure D1. Distribution of age (sample size=1326 patients). Male Female Unknown 0% 53% 47% Figure D2. Distribution of gender (sample size=1326 patients).

139 miles miles >100 miles 13% 45% 42% Figure D3. Distribution of the number of miles travelled to UICOD (sample size=1326 patients). Dental Insurance Self-Pay Medicaid 15% 37% 48% Figure D4. Distribution of dental insurance status (sample size=1326 patients).

140 % 8% 16% 64% Figure D5. Distribution of the total number of recalls and prophy exams before the 18 month stepwise excavation procedure was performed (sample size=1326 patients). 0 Restoration 1 Restoration 2 Restorations 3+ Restorations 8% 11% 17% 64% Figure D6. Distribution of the total number of restorations per patient18 months before stepwise excavation procedure was performed (sample size=1326 patients).

141 126 Incisors Canines Premolars Molars 11% 8% 52% 29% Figure D7. Distribution of tooth type (sample size= 1326 patients). Maxillary Mandibular 45% 55% Figure D8. Distribution of tooth arch (sample size= 1326 patients).

142 % 8% 3% 22% 44% Figure D9. Distribution of the number of surfaces treated in first appointment of SWP (sample size= 1326 patients). Undergrad Resident Faculty 5% 10% 85% Figure D10. Distribution of the type of provider that performed first appointment SWP (sample size=1326 patients).

143 128 APPENDIX E. UNIVARIATE, BIVARIATE AND LOGISTIC REGRESSION ANALYSIS BY PATIENT Basic descriptors per patient Table E1. Descriptive statistics for patient age at the time of SWP, the time in months before re-evaluation/re-entry, and the miles travelled to the UICOD. Variable N N Miss Mean Std Dev Std Error Median Minimum Maximum AGE Months interval for all patients Number of months for patients that returned Miles Table E2 Frequency distribution of gender for all patients (1326) GENDER Frequency Percent Female Male Frequency Missing = 1

144 129 Table E3 Frequency distribution of type of dental insurance at the time of the SWP for all patients (1326) Dental Insurance Status Frequency Percent Dental Insurance Self Pay Medicaid Table E4 Frequency distribution for calendar year of treatment at the time of the SWP for all patients (1326) Treatment Year Frequency Percent Table E5 Frequency distribution for provider level for all patients (1326) PROVIDERLEVEL Frequency Percent Faculty Resident Undergraduate

145 130 Table E6 Frequency distribution for tooth type for all patients (1326) TOOTHTYPE Frequency Percent Cumulative Frequency Cumulative Percent Canines Incisors Molars Premolars Table E7 Frequency distribution for tooth arch for all patients (1326) TOOTHARCH Frequency Percent Cumulative Cumulative Frequency Percent Mandibular Maxillary Table E8 Frequency distribution for number of surfaces in the treated tooth for all patients (1326) Total Surfaces Frequency Percent Cumulative Frequency Cumulative Percent Frequency Missing = 603

146 131 Table E9 Frequency distribution for the number of recall examinations and prophy visits in the 18 months prior to the SWP for all patients (1326) RECALLS Frequency Percent Cumulative Cumulative Frequency Percent Table E10 Frequency distribution for the total number of restorations at the UICOD in the 18 months prior to the SWP. RESTORS Frequency Percent Cumulative Cumulative Frequency Percent Table E11. Summary table for frequency distribution of study variables, number of recall exams and total number of restorations 18 months prior to SWP calculated for all patients (1326) Variable RECALLS RESTORATIONS N Mean Std Dev Std Error Median 0 0 Minimum 0 0 Maximum 15 20

147 132 Table E12. Driving distance to the UI College of Dentistry for the 1,326 study participants. DISTANCE Frequency Percent <35 MILES MILES >100 MILES Basic descriptors for patients divided by re-entry status Table E13. Single record analysis for patients within the 18 month window. In Window Re-Entered No Yes Total No Yes Total Table E14. Descriptive statistics for quantitative covariates for patients that had re-entry. Variable N Mean Std-Dev Median Minimum Maximum Age Miles Total surfaces Days

148 133 Table E15. Frequency distribution for gender with and without re-entry Gender Frequency Percent Cumulative Frequency Cumulative Percent Female RE-ENTRY Male Unknown NO Female RE-ENTRY Male Unknown Table E16. Frequency distribution of patients that had dental insurance divided by reentry status (0=NO; 1=YES). Dental Insurance Frequency Percent Cumulative Frequency Cumulative Percent RE-ENTRY NO RE-ENTRY Table E17. Frequency distribution of self-pay patients by re-entry status (0=NO; 1=YES). Self- pay Frequency Percent Cumulative Frequency Cumulative Percent RE-ENTRY NO RE-ENTRY

149 134 Table E18. Frequency distribution of Medicaid patients by re-entry status (0=NO; 1=YES). Medicaid Frequency Percent Cumulative Frequency Cumulative Percent RE-ENTRY NO RE-ENTRY Table E19. Frequency distribution of sedative filling restorations for patients that had reentry (0=NO; 1=YES). Sedative filling Frequency Percent Cumulative Frequency Cumulative Percent Table E20. Frequency distribution of glass ionomer restorations for patients that had reentry (0=NO; 1=YES). Glass ionomer Frequency Percent Cumulative Frequency Cumulative Percent

150 135 Table E21. Frequency distribution of amalgam restorations for patients that had re-entry (0=NO; 1=YES). Amalgam Frequency Percent Cumulative Frequency Cumulative Percent Table E22. Frequency distribution of resin composite restorations for patients that had reentry (0=NO; 1=YES). Resin composite Frequency Percent Cumulative Frequency Cumulative Percent Table E23. Frequency distribution of inlays and onlays restorations for patients that had re-entry (0=NO; 1=YES). Inlay/Onlay Frequency Percent Cumulative Frequency Cumulative Percent Table E24. Frequency distribution of crown restorations for patients that had re-entry (0=NO; 1=YES). Crown Frequency Percent Cumulative Frequency Cumulative Percent

151 136 Table E25. Frequency distribution of root canal treatments (RCT) for patients that had reentry (0=NO; 1=YES). RCT Frequency Percent Cumulative Frequency Cumulative Percent Table E26. Frequency distribution of tooth extraction procedures (TE) for patients that had re-entry (0=NO; 1=YES). TE Frequency Percent Cumulative Frequency Cumulative Percent Table E27. Frequency distribution of implant procedures for patients that had re-entry (0=NO; 1=YES). Implant Frequency Percent Cumulative Frequency Cumulative Percent

152 137 Bivariate Analysis Table E28. Table of re- entry status by gender. The Chi square test values for this table corresponds to χ2 = 0.62; df=1; p=0.43 STATUS GENDER(GENDER) Female Male Total NO RE-ENTRY RE-ENTRY Total Frequency Missing = 1 Table E29. Table of re-entry status by tooth arch. The Chi square test values for this table corresponds to χ2 = 0.37; df=1; p=0.55 STATUS TOOTH ARCH (TOOTH ARCH) Mandibular Maxillary Total NO RE-ENTRY RE-ENTRY Total

153 138 Table E30. Table of re-entry status by dental insurance status. The Chi square test values for this table corresponds to χ 2 = 11.00; df=2; p= Dental Insurance Status STATUS Dental Insurance Self -Pay Medicaid Total NO RE ENTRY RE-ENTRY Total Table E31. Table of re-entry status by provider level. The Chi square test values for this table corresponds to χ 2 = 26.17; df=2; p< STATUS PROVIDERLEVEL(PROVIDERLEVEL) Faculty Resident Undergrad Total NO RE ENTRY RE-ENTRY Total Table E32. Table of Re-entry status by tooth type. The Chi square test values for this table corresponds to χ 2 = 20.30; df=3; p= STATUS NO RE- ENTRY RE- ENTRY TOOTH TYPE (TOOTH TYPE) Canines Incisors Molars Premolars Total Total

154 139 Table E33. Table of Re-entry status by treatment year. The Chi square test values for this table corresponds to χ2 = 21.52; df=8; p=0.0059, and based upon the Wilcoxon Rank Sum test (p = ) Treatment Year STATUS Total NO RE ENTRY RE ENTRY Total Table E34. Table of Re-entry status by number of surfaces. The Chi square test values for this table corresponds to (χ 2 = 10.82; df=8; p=0.029), and based upon the Wilcoxon Rank Sum test (p=0.99) STATUS Total Surfaces(Total Surfaces) Total NO RE-ENTRY RE-ENTRY Total Frequency Missing = 603

155 140 Table E35. Table of Re-entry status by total number of recall exams (Wilcoxon Rank Sum test; p < ) STATUS NO RE-ENTRY RE-ENTRY Total RECALLS Total Table E36. Table of Re-entry status by total number of number of miles traveled to UICOD Wilcoxon Rank Sum test; p=0.25 STATUS NO RE-ENTRY RE-ENTRY Total DISTANCE MILES <35 MILES >100 MILES Total

156 141 Table E37. Table of Re-entry status by total number restorations per patient (Wilcoxon Rank Sum test; p = 0.22) STATUS NO RE-ENTRY RE-ENTRY Total TOTAL NUMBER RESTORATIONS Total Table E38. Descriptive statistics of quantitative variables, comparing subgroups based on re-evaluation/re-entry status at 18 months after performance of stepwise excavation procedure. Variable N Mean STATUS=NO RE-ENTRY Std Dev Std Error Median Minimum Maximum Age Miles Total Surfaces RECALLS (18 months before SWP) RESTORATIONS 18 months before SWP) TreatmentYear

157 142 Table E39. Descriptive statistics of quantitative variables, comparing subgroups based on re-evaluation/re-entry status at 18 months after performance of stepwise excavation procedure. STATUS=RE-ENTRY Variable N Mean Std Dev Std Error Median Minimum Maximum Age Miles Total Surfaces RECALLS (18 months before SWP) RESTORATIONS (18 months before SWP) TreatmentYear Logistic regression modeling Table E40. Significance probabilities for factors in the final model after adjustment for the other covariates in the model Effect DF Wald Pr > ChiSq Chi- Square PROVIDER LEVEL TOOTH TYPE <.0001 RECALLS <.0001 TREATMENT YEAR AGE <.0001

158 143 Table E41. Analysis of maximum likelihood estimates associated with the logistic regression coefficients (β s). Parameter DF Estimate Standard Wald Pr > ChiSq Chiof β Error Square Intercept PROVIDER LEVEL Faculty PROVIDER LEVEL Resident TOOTH TYPE Canines TOOTH TYPE Molars TOOTH TYPE Premolars RECALLS <.0001 TREATMENT YEAR AGE <.0001 * Number of recall/prophy visits at the UI COD within 18 months prior to the performance of the SWP. Table E42. Odds Ratio Estimates. Effect Point Estimate 95% Wald of OR Confidence Limits PROVIDERLEVEL Faculty vs Undergraduate PROVIDERLEVEL Resident vs Undergraduate TOOTHTYPE Canines vs Incisor TOOTHTYPE Molars vs Incisor TOOTHTYPE Premolars vs Incisor RECALLS 18 months before SWP TREATMENT YEAR AGE * Number of recall/prophy visits at the UI COD within 18 months prior to the performance of the SWP.

159 144 Table E43. Results from Multiple Logistic Regression Modeling of Completion of Re- Evaluation/Re-Entry within 18 Months of Stepwise Excavation Procedure. INDEPENDENT VARIABLE PROVIDER LEVEL p = Point Estimate of OR 95% Wald Confidence Limits Faculty vs Undergraduate Resident vs Undergraduate TOOTH TYPE p < Canines vs Incisor Molars vs Incisor Premolars vs Incisor RECALLS p < TREATMENT YEAR p = AGE p < Table E44. Provider Level by Insurance Status. For each provider, the frequency observed (top row) and expected under independence (bottom row) is shown. Provider Level Insurance Status Dental Insurance Self- Pay Medicaid Total Faculty Resident Undergraduate Total

160 145 Supporting figures for Statistical Analysis Figure E1. Geographic distribution of the reported zip code of reported patient residence; the dark dot in southeastern Iowa indicates the location of the UI College of Dentistry.

161 Figure E2. Geographic distribution of the reported zip code of reported patient residence within a one-state radius of the UI College of Dentistry; the dark dot in southeastern Iowa indicates the location of the College of Dentistry. 146