A RETROSPECTIVE STUDY OF STAINLESS STEEL CROWNS AS A POSTERIOR PERMANENT TOOTH RESTORATION

Transcription

1 A RETROSPECTIVE STUDY OF STAINLESS STEEL CROWNS AS A POSTERIOR PERMANENT TOOTH RESTORATION by Alison Sigal A thesis submitted in conformity with the requirements for the degree of Master of Science in Pediatric Dentistry Graduate Department of Dentistry University of Toronto Copyright by Alison Sigal (2016)

2 RETROSPECTIVE STUDY OF STAINLESS STEEL CROWNS AS A POSTERIOR PERMANENT TOOTH RESTORATION Alison Sigal Master of Science Pediatric Dentistry, University of Toronto 2016 Abstract Purpose: This retrospective cohort study assessed the long-term clinical and radiographic outcomes of the stainless steel crown (SSC) as a posterior permanent tooth restoration. Methods: Study included 271 patients registered at Mount Sinai Hospital s Dentistry Clinic for Persons with Special Needs. A total of 2621 posterior restorations were documented: 766 SSCs, 1651 amalgams, and 204 composite resins. Radiographic analysis of SSCs included 127 bitewing, and 118 periapical films. Results: Ten year survival rate for new SSC and amalgam restorations was 79.2% and 63.5%, respectively. Ninety-one SSC failures included loose/lost SSCs (24) and chronic periodontal disease (25). Ninety-three percent of alveolar bone loss measurements from mesial and distal sites were <2mm and classified as healthy. All pre and post SSC PA s had healthy periapical scores recorded over an average duration of 8.4 years. Conclusion: SSCs represent a cost-effective, durable and preferred treatment option for the restoration of the posterior permanent dentition. ii

3 Dedicated to the Two Greatest and Most Influential Men in my Life My Father, Dr. Michael J. Sigal And My Husband, Brian M.S. Granby iii

4 ACKNOWLEDGEMENTS To my supervisors, Drs. P. Andrews and A. Azarpazhooh for sharing your passion for research, and guiding me throughout my MSc journey. To my committee members, Drs. K. Titley and H. Tenenbaum for your encouragement, insight, and care. It was an honour to have you on my committee. To Dr. Ellen Maki for your invaluable statistical wizardry, patience, and support. To Trevor Thang who turned my idea of a unique triple-decker database, into a brilliant reality. To Drs. M. Goldberg and A. Moncarz for your time in the standardization process of radiographic observations. To my Paediatric family & Friends from both near and far From the bottom of my heart, I thank you for your endless love, support, and encouragement. To my Mom and Dad whom have taught me life s most valuable lessons. You are the greatest of role models, and your love and support have made me who I am today. Thank you for always believing in me, and teaching me that no dream is too big. Your love, strength, and passion for following your heart, will always be an inspiration. Finally, to my husband and best friend, Brian Granby. You are the love and best part of my life; words could never express my gratitude for your endless love and support. You are my constant motivation and inspiration. Together we can forever and always. iv

5 TABLE OF CONTENTS Abstract... ii Dedication.. iii Acknowledgements... iv Table of Contents... v List of Tables... ixx List of Figures... xii List of Appendices... xiiii A. Review of Literature History of the Stainless Steel Crown Restoration Indications and Utilization of SSC Restorations... 3 (a) Primary Dentition: Indications... 3 (b) Primary Dentition: Utilization of SSCs... 4 (c) Permanent Dentition: Indications... 6 (d) Permanent Dentition: Utilization of SSCs Emerging Applications for the Use of SSC Restorations... 8 (a) Persons with Special Needs... 9 (b) Adjunctive Use of General Anesthetic... 9 (c) Geriatric Populations (d) Persons with Limited Finances or Dental Coverage Methods Used in Previous Clinical Studies of Restorative Materials (a) Clinical Outcomes for Stainless Steel Crown Restorations (b) Clinical Outcomes for Multisurface Intra Coronal Direct Restorations (c) Lab Fabricated Crown Clinical Outcomes ) Radiographic Evaluation and Outcomes v

6 (a) Pulpal Status (b) Periodontal Status Purpose of the Study B. Expected Outcomes C. Aims and Objectives D. Materials and Methods Sample Data Collection (a) Part 1: Demographic and Dental Information Collection (b) Part 2: Radiographic Assessment of SSC Restorations Data Analysis E. Results Pilot Study Agreement Analysis and Standardization Part 1: Patient Demographics and Dental Treatment (a) Medical History (b) Dental History (c) Behaviour (d) Dental Restorations (e) Failed Dental Restorations (i) Failed Dental Restorations: Stainless Steel Crowns (ii) Failed Dental Restorations: Amalgam Restorations (iii) Failed Dental Restorations: Composite Resin Restorations (iv) Failed Dental Restorations: New versus Pre-Existing (v) Summary Table (f) Ten Year Survival Rate Estimate vi

7 (g) Crude Success Rates for New SSC and Amalgam Restorations Part 2: Radiographic Assessment of SSC Restorations (a) Alveolar Bone Loss Measurements (b) Periapical Index (PAI) Scores and Pulpal Status of SSC restored teeth F. Discussion Stainless Steel Crown Restorations (a) Stainless Steel Crown Reported Failures (b) Stainless Steel Crown Survival Analysis Conventional Restorative Treatments (a) Conventional Restoration Reported Failures (b) Survival Analysis of Conventional Restorations (c) Replacement of Conventional Restorations with SSCs Radiographic Evaluation (a) Pulpal Status of SSC Restored Teeth (b) Alveolar Bone Measurements of SSC Restored Teeth (c) Limitations of Radiographic Evaluation Data Analysis (a) Agreement Analysis (b) Inferential Statistics (c) Cox Proportional Hazards Model and Logrank Tests (d) Multivariate Cox Proportional Hazards (PH) Regression for Each Restoration Type Demographics and Implication for Practice Limitations and Strengths Future Directions G. Conclusions vii

8 Tables and Figures Literature Cited viii

9 List of Tables Table 1. Study Population and Gender Distribution Table 2. Study Population Age Distribution Summary Table 3. Distribution of Medical Conditions amongst Study Population Table 4. Most Common Medical Conditions amongst Study Population Table 5. Number of Patients with Multiple Co-Morbidities Table 6. Distribution of Medications Prescribed amongst Study Population Table 7. Most Commonly Prescribed Medications amongst Study Population Table 8. Insurance Coverage Distribution Table 9. Caries Risk, Oral Hygiene and Recall Frequency Table 10. Frankl Scale of Patient Behaviour/Cooperation Table 11. Number of Subjects, Teeth, and Restorations Table 13. Number of Male Subjects, Teeth, and Restorations Table 14. Number of Female Subjects, Teeth, and Restorations Table 15. Number of Restorations by Tooth Location Table 16. Number of Restorations by Specific Tooth Table 17. Distribution of All Restorations by Tooth Location and Male Gender Table 18. Distribution of All Restorations by Tooth Location and Female Gender Table 19. Number of Censored Observations including All Restoration Types Table 20: Distribution of Diagnoses for Placement of SSC and Amalgam Restorations Table 23. Distribution of SSC Occlusal Perforations Table 24. Diagnoses for Specific Amalgam Restoration Failures Replaced with New Restorations Table 27. Diagnoses for Composite Resin Restoration Failures Replaced with New Restorations ix

10 Table 28. Number and Distribution of All New Restorations Table 29. Distribution and Number of All Pre-existing Restorations Table 31. Product-Limit Estimate of Longevity for All Stainless Steel Crown Restorations 117 Table 32. Product-Limit Estimate of Longevity for New SSC Restorations Table 33. Product-Limit Estimate of Longevity for Pre-existing SSC Restorations Table 34. Follow-up by Subject and by Restoration Type for All Restorations Table 35. Product-Limit Estimate of Longevity for All Amalgam Restorations Table 36. Product-Limit Estimate of Longevity for New Amalgam Restorations Table 37. Product-Limit Estimate of Longevity for Pre-existing Amalgam Restorations Table 38. Product-Limit Estimate of Longevity for Pre-existing Composite Resin Restorations Table 39. Product-Limit Estimate of Longevity of New SSC Restorations by Age Group Table 40: Product-Limit Estimate of Longevity of New Amalgam Restorations by Age Group Table 41. Product-Limit Estimate of Longevity of New SSC Restorations by Gender Table 42. Product-Limit Estimate of Longevity of New Amalgam Restorations by Gender 141 Table 43. Product-Limit Estimate of Longevity of New SSC Restorations by Location (Upper vs. Lower) Table 44. Product-Limit Estimate of Longevity of New Amalgam Restorations by Location (Upper vs. Lower) Table 45. Crude Success Rates for New SSC and Amalgam Restorations Table 47. Duration Between Pre and Post SSC Periapical Radiographs x

11 List of Figures Figure 1. Gender Distribution of Study Population Figure 2. Age of Study Population as of March 31 st, Figure 3. Age of Study Population at First Clinic Visit Figure 4. Age of Study Population at Time of First Restoration Figure 5. Number of Teeth Restored Per Subject by Type of Restoration Figure 6. Number of Restorations Per Subject by Type of Restoration Figure 7. Number of Restorations Per Tooth Figure 8. Number of Restorations Recorded by Type Figure 9. Number of Restorations by Tooth Location Upper/Lower Figure 10. Number of Restorations by Tooth Location Left/Right Figure 11. Number of Restorations by Tooth Location Upper/Lower and Left/Right Figure 12. Number of Restorations by Specific Tooth for All Restoration Types Figure 13. Number of Restorations by Specific Tooth for SSC Restorations Figure 14. Number of Restorations by Specific Tooth for Amalgam Restorations Figure 15. Number of Restorations by Specific Tooth for Composite Resin Restorations Figure 16. Number of Failures Recorded by the End of Study for All Restoration Types Figure 17. Non-censored Number and Distribution of New Restoration Failures Figure 18. Number of Failures by End of Study for All Pre-existing Restorations Figure 19. Survival Curve and 95% CI for All SSC Restorations Figure 20. Survival Curve and 95% CI for New SSC Restorations Figure 21. Survival Curve and 95% CI for Pre-existing SSC Restorations Figure 22. Follow-up Time in 5-year Increments by Subject Figure 23. Follow-up Time in 5-year Increments by Restoration Type for All Restorations xi

12 Figure 24. Survival Curve and 95% CI for All Amalgam Restorations Figure 25. Survival Curve and 95% CI for New Amalgam Restorations Figure 26. Survival Curve and 95% CI for Pre-existing Amalgam Figure 27. Survival Curve and 95% CI for Pre-existing Composite Resin Restorations Figure 28. Survival Curve Comparison Between All Amalgam and SSC Restorations Figure 31. Survival of New SSC Restorations by Different Age Groups at Time of Placement Figure 32. Survival of New Amalgam Restorations by Different Age Groups at Time of Placement Figure 33. Survival of New SSC Restorations by Gender Figure 34. Survival of New Amalgam Restorations by Gender Figure 35. Survival of New SSC Restorations by Location (Upper vs. Lower) of Placement Figure 36. Survival of New Amalgam Restorations by Location (Upper vs. Lower) of Placement Figure 37. Crude Success Rates for New SSC and Amalgam Restorations xii

13 List of Appendices APPENDIX 1: DEMOGRAPHICS A) Screenshots of Database for Appendix 1 Data Collection B) Patient Demographics C) Family History D) Medical Information i) Central Nervous System ii) Cardiovascular System iii) Respiratory System iv) Gastrointestinal System v) Immune System vi) Genito-Urinary System vii) Endocrine System viii) Musculoskeletal System ix) Dermatology E) Medications at the Present Time F) Previous Surgical Experience G) Dental Information APPENDIX 2: DENTAL TREATMENT DATABASE A) Screenshots of Database for Appendix 2 Data Collection B) Dental Treatment Data Collection APPENDIX 3: RADIOGRAPHIC ASSESSMENT DATABASE A) Screenshots of Database for Appendix 3 Data Collection APPENDIX 4: PERIAPICAL INDEX REFERENCE xiii

14 Reference Radiographs/Line Drawings with Periapical Index (PAI) Scores APPENDIX 5: PILOT STUDY AGREEMENT ANALYSIS xiv

15 A. REVIEW OF LITERATURE 1. History of the Stainless Steel Crown Restoration The preformed metal crown (PMC), more commonly known in North America as the stainless steel crown (SSC), was first described in 1950 by Engel and Humphrey (Engel, 1950). By definition SSCs are prefabricated full coverage crown forms that are adapted to individual teeth and cemented with a biocompatible luting agent (Titley and Farkouh, 2001). The goal of the restoration is to reestablish the coronal tooth structure lost due to caries, fracture, or malformation and maintain a healthy periodontium, vertical dimension and arch length (Croll, 1999). Since 1950, several design modifications to the SSC have been made to simplify the fitting procedure and improve the morphological features of the crown. Placement of a SSC has since been recognized as a relatively simple restorative treatment modality to employ requiring minimal tooth preparation and crown adaptation (Fieldman and Cohen, 1979; Titley and Farkouh, 2001). In addition, SSCs have proven to be extremely durable, relatively inexpensive and available for the restoration of both primary and permanent dentitions (Randall, 2002; Seale, 2002; Seale and Randall, 2015). Each of these attributes has contributed to the success and recognition of the SSC as a highly effective primary molar restoration (Kindelan et al., 2008). Between, 1975 and 2002, several retrospective studies have examined the longevity of SSC restorations in the primary dentition. The reported outcomes have demonstrated that SSCs consistently outperformed: multi-surface amalgam (Braff, 1975; Dawson et al., 1981; Einwag and Dunninger, 1996; Messer and Levering, 1988), glass ionomer cements, and composite resin 1

16 2 restorations (Al-Eheideb and Herman, 2003; Drummond et al., 2004; Eriksson et al., 1988; O'Sullivan and Curzon, 1991; Papathanasiou et al., 1994; Tate et al., 2002) on primary molars. The superiority was observed consistently despite the fact that the investigations were carried out in heterogeneous patient populations, using crowns from various manufacturers, and in several different centers. Recently, Seale and Randall (2015) published a systematic literature review, updating the use and recommendations of stainless steel crowns. Sixty-one papers were assessed, consisting of 24 clinical studies, 3 case reports, 21 reviews and 13 in vitro studies. Stainless steel crowns continue to be superior in both durability and longevity as compared to amalgam and resin-based restorations in the primary dentition. Minimal evidence exists to support the economic value of multi-surface restorations over SSCs; and for children requiring general anesthesia, SSC restorations should be considered the treatment of choice for primary molars. This is supported by the widely accepted advantages of SSC restorations, that include: full coronal coverage reducing potential of recurrent caries, strength and long-term durability with minimal maintenance (Seale and Randall, 2015). As a result, in pediatric dentistry practices, SSCs continue to be the restoration of choice for moderate to severely compromised primary molar teeth (Dawson et al., 1981; McKnight-Hanes et al., 1991; Messer and Levering, 1988; Seale and Randall, 2015; Titley and Farkouh, 2001).

17 3 2. Indications and Utilization of SSC Restorations (a) Primary Dentition: Indications Numerous authors have published the indications for use of SSCs in the primary dentition, but to date, a single comprehensive list has not been agreed upon. The indications described in the reported studies include: i) Following pulp therapy (Albers, 1979; Allen, 1966; Brook and King, 1982; Croll, 1993, 1999; Croll and Riesenberger, 1986; M. S. Duggal and Curzon, 1989; Goldberg, 1969; Henderson, 1973; Hinding, 1976; Mink and Bennett, 1968; More and Pink, 1973; Myers, 1976; Nash, 1981; Page, 1973; Rapp, 1966; Seale and Randall, 2015). ii) Restoration of multisurface caries in persons with high caries risk (Allen, 1966; Brook and King, 1982; Croll, 1999; Croll and Riesenberger, 1986; M. S. Duggal and Curzon, 1989; Fieldman and Cohen, 1979; Goldberg, 1969; Henderson, 1973; Hinding, 1976; Mink and Bennett, 1968; More and Pink, 1973; Myers, 1976; Nash, 1981; Rapp, 1966; Seale and Randall, 2015). iii) Restoration of primary teeth with developmental enamel or dentinal defects (Allen, 1966; Brook and King, 1982; Croll, 1993, 1999; M. S. Duggal and Curzon, 1989; Fieldman and Cohen, 1979; Goldberg, 1969; Hinding, 1976; Mink and Bennett, 1968; More and Pink, 1973; Myers, 1976; Nash, 1981; Page, 1973; Seale and Randall, 2015). iv) Clinical scenarios where amalgam is likely to fail (i.e. caries extending beyond clinical crown line angles) (Brook and King, 1982; Henderson, 1973; Nash, 1981; Pinkerton, 2001).

18 4 v) Treatment of traumatic dental fracture not suitable for an intra- coronal restoration (Croll, 1999; Croll and Riesenberger, 1986; M. S. Duggal and Curzon, 1989; Goldberg, 1969; Mink and Bennett, 1968; More and Pink, 1973; Rapp, 1966; Seale and Randall, 2015). vi) Teeth with extensive wear (M. S. Duggal and Curzon, 1989; Fieldman and Cohen, 1979). vii) Abutment for space maintainer (Allen, 1966; Brook and King, 1982; Croll, 1999; Croll and Riesenberger, 1986; M. S. Duggal and Curzon, 1989; Fieldman and Cohen, 1979; Goldberg, 1969; Mink and Bennett, 1968; More and Pink, 1973; Rapp, 1966). viii) Persons with special needs or children who require the use of general anesthesia (GA) for their dental care (Al-Eheideb and Herman, 2003; Burtner and Dicks, 1994; Drummond et al., 2004; Melville et al., 1981; Nunn et al., 1995; Seale and Randall, 2015; Titley and Farkouh, 2001) (b) Primary Dentition: Utilization of SSCs Despite extensive support for the use of SSCs, many authors report that this treatment approach for the restoration of the primary posterior dentition is underutilized by general dentists (Berman, 1994; Casamassimo, 1994; Croll and Killian, 1992; M. S. Duggal and Curzon, 1989; Page, 1973). The reasons for underutilization include poor or absent undergraduate didactic training in the use of SSCs, lack of clinical experience in the placement of SSCs, and the belief that the provision of a SSC is a complex procedure (Berman, 1994; Casamassimo, 1994; Croll and Killian, 1992; M. Duggal et al., 1995; M. S. Duggal and Curzon, 1989; Page, 1973; Seale and Randall, 2015). In reality, the SSC restoration is a straightforward technique (Berman, 1994; M.

19 5 S. Duggal and Curzon, 1989; Full et al., 1974) and is often simpler to complete and more costeffective than a Class II direct restoration (Kindelan et al., 2008). Given the longevity, reliability and effectiveness of SSCs (Roberts and Sherriff, 1990), the British Society of Paediatric Dentistry (BSPD) has stated that SSCs are the restoration of choice for primary molars with extensive caries and/or require pulp therapy (Threlfall et al., 2005). In spite of this clear policy statement, data from the Dental Practice Board indicated that general dental practitioners (GDPs) continue to underutilize SSCs. National Health Service (NHS) general dental practice data in 2002 recorded that 3,129 SSCs were placed on primary teeth by GDPs, while 25,370 vital pulpotomies and 59,512 non-vital primary root canals had been undertaken on primary teeth during the same period (Threlfall et al., 2005). Given the recommendations made by the BSPD for restorative management of teeth treated for pulpal disease, only 3.7% of teeth were managed properly, having received the recommended SSC restoration. In this study, the GDPs provided personal and practical reasons for not placing SSCs. Many believed they were unnecessarily durable for the primary dentition, not cosmetically acceptable, and that glass ionomer was quicker, more clinically acceptable and tolerable for their patients. Some GDPs reported they had not received sufficient training, while others believed the reimbursement to be inadequate (Threlfall et al., 2005). McKnight-Hanes et al. (1991) compared general dentists and pediatric dentists treatment recommendations for primary teeth based on radiographic and clinical information. For these cases, irrespective of whether pulp therapy was recommended, general dentists frequently recommended restoring teeth with amalgam, while pediatric dentists recommended SSCs. The explanation provided for such observed differences related to the practitioner s education and experience. The advanced education of pediatric dentists was noted as providing greater

20 6 familiarity with SSC techniques, and an awareness of the limited life span of complex amalgams in primary teeth (Dawson et al., 1981; McKnight-Hanes et al., 1991; Messer and Levering, 1988). It has been suggested that postgraduate training, and in particular hands-on training courses, may be the most effective way to encourage dentists to re-evaluate their restorative techniques and increase the use of SSC restorations for the primary dentition (Kindelan et al., 2008). (c) Permanent Dentition: Indications In permanent posterior teeth, the main advantage for the use of SSC s is to provide full-coronal interim coverage that is effective, durable, and reliable while circumstances preclude potential additional treatment (i.e. lab fabricated crowns, endodontic treatment, etc.) (Croll, 1999). With respect to the use of the term, interim above, this refers to any time period ranging from a few months, to a decade and beyond (Croll, 1999). There is a paucity of literature regarding the indications for use of SSCs as restorations for permanent molars or premolars. Some examples that have been proposed include: i) Interim restoration of grossly decayed or traumatized teeth (Croll, 1999; Croll and Castaldi, 1978; Goldberg, 1969; Gordon, 1979; Kimmelman and Riesner, 1977; Mink and Bennett, 1968; Page, 1973; Radcliffe and Cullen, 1991; Roberts, 1983; Seale and Randall, 2015). ii) Interim restoration of teeth being considered for orthodontic extraction (Brook and King, 1982; Croll, 1987).

21 7 iii) Medium-term, economical restoration of permanent teeth (Croll, 1987; Gordon, 1979; Murray and Madden, 1997). iv) Teeth with developmental enamel or dentinal defects (Brook and King, 1982; Croll, 1999; Croll and Castaldi, 1978; M. S. Duggal and Curzon, 1989; Kimmelman and Riesner, 1977; Mink and Bennett, 1968; Radcliffe and Cullen, 1991; Seale and Randall, 2015). v) Restoration of a partially erupted permanent molar (Brook and King, 1982; Croll, 1999; Rapp, 1966). vi) Restoration of teeth in persons with special needs whom require the use of general anesthesia for dental care (Burtner and Dicks, 1994; Melville et al., 1981; Nunn et al., 1995; Titley and Farkouh, 2001). vii) Persons who are uncooperative and/or from remote areas without regular access to dental care (Titley and Farkouh, 2001). (d) Permanent Dentition: Utilization of SSCs Despite the multitude of recommendations and applications for the use of SSCs as a restorative treatment option for the permanent dentition, there is a paucity of literature reporting clinical outcomes. The majority of the published research regarding SSC restorations in the permanent dentition is based upon anecdotal evidence, case reports or studies with small sample sizes and minimal follow up periods. Zagdwon, Fayle and Pollard (2003) compared SSCs and nickel-chrome (NiCr) alloy cast crowns for restoration of permanent first molars with severe enamel defects. Forty-two restorations were

22 8 placed (19 SSCs, 23 NiCr crowns) in 17 adolescents with a mean follow up of 17 months. There was no statistically significant difference between the two types of restorations in terms of quality or longevity. However, the authors concluded that although it was possible to do a minimal preparation design for the NiCr crowns, it was more technique sensitive, required multiple visits and was less cost effective as compared to the traditional SSC (Zagdwon et al., 2003). Roberts and Sherriff (1990) evaluated 43 permanent molar SSCs with conventional restorations. This study reported the overall replacement over a 10-year follow-up of SSCs was 2.3% (i.e. almost 98% of SSCs placed did not have to be re-treated). The primary reason for failure was due to occlusal perforation. In comparison, 11% of amalgam restorations failed due to recurrent decay (Roberts and Sherriff, 1990). Despite the promising results, both aforementioned studies had very small sample sizes of permanent molar SSC restorations, and were therefore not generalizable to the profession at large (Roberts and Sherriff, 1990; Zagdwon et al., 2003). 3. Emerging Applications for the Use of SSC Restorations Stainless steel crown restorations for the permanent dentition represent an important treatment option for several populations. These include: persons with special needs, persons requiring adjunctive use of general anesthetic, geriatric populations, and persons with limited finances/dental coverage (Bohaty and Spencer, 1992; Burtner and Dicks, 1994; Melville et al., 1981; Nunn et al., 1995; Seale and Randall, 2015; Titley and Farkouh, 2001).

23 9 (a) Persons with Special Needs Adults with special needs are known to have high risk for and prevalence of caries and as such are highly likely to have SSC restorations placed on their permanent posterior teeth (Chohayeb, 1985; Tesini, 1981). A person with special needs is defined as any individual with a congenital or acquired impairment that causes long-term adverse effects upon their ability to perform daily activities typical for their stage of development (Accardo et al., 2002; Merry and Edwards, 2002; World Health Organization., 2001). The adverse effects or functional limitations may include cognitive, receptive, expressive language, learning, and/or motor ability deficits (Accardo et al., 2002; Merry and Edwards, 2002; World Health Organization., 2001). Stainless steel crown restorations for the permanent posterior dentition are recommended for the subgroup of individuals who are unable to maintain good oral hygiene and who have extensive dental caries (Chohayeb, 1985). The full coronal coverage that SSCs supply virtually ensures that recurrent decay will not occur and, their smooth surfaces render the tooth easier to clean using routine oral hygiene procedures compared to that of other restorative treatments (Chohayeb, 1985; Seale and Randall, 2015; Titley and Farkouh, 2001). As such, the placement of SSC restorations could significantly reduce the incidence of recurrent caries and increase the likelihood of maintaining the patient s existing dentition (Titley and Farkouh, 2001). (b) Adjunctive use of General Anesthetic The adjunctive use of general anesthetic for dental care has been generally accepted and reported. The published indications include (Bohaty and Spencer, 1992; Melville et al., 1981; Nunn et al., 1995; Titley and Farkouh, 2001):

24 10 i) Extreme non-cooperation, anxiety and fearfulness of the child ii) Persons with medical conditions who require significant dental care iii) Persons with special needs iv) Persons with extensive dental treatment needs but who are from remote areas and therefore have poor or no access to regular dental care v) Persons with an allergy to local anesthetics vi) Very young children with extensive caries The availability of GA facilities to dentists and their patients is limited and the waiting lists can be extensive. As a result, the majority of patients in need of a GA for the provision of their dental care, especially those without regular access to dental care, often present with large multi-surface carious lesions (Burtner and Dicks, 1994; Chohayeb, 1985; Tesini, 1981; Titley and Farkouh, 2001). The frequency that such patients would need to be re-exposed to general anesthetic is directly related to the development of new caries and/or the need to re-treat failed restorations (Al-Eheideb and Herman, 2003; Drummond et al., 2004; Nunn et al., 1995; Seale, 2002). As such, a strong economic argument can be made for the use of SSCs based on their longevity and full coronal coverage that would reduce the frequency of re-treatment. Given the known risks associated with the use of GA, there is also a strong biomedical argument for use of SSCs based on their longevity that would reduce the potential frequency of re-exposure (to GA) (Al-Eheideb and Herman, 2003; Drummond et al., 2004; Seale, 2002).

25 11 (c) Geriatric Populations In 1998, Ettinger et al. documented a growing indication for SSC placement in the permanent posterior dentition of geriatric patients. In most of the developed world, people are living longer and retaining their natural dentition. However these patients often require full-coronal restorations to replace large failing restorations; a treatment approach that might be beyond their ability to pay, due to the average lower income levels demonstrated in the aged (Statistics Canada, 2014). It is noteworthy then, that a properly adapted SSC can be a practical, less expensive, convenient, and effective alternative to a traditional laboratory-processed crown. In addition the placement of a SSC requires a single relatively short appointment versus several longer appointments, which represents a significant advantage in a population that often find tolerating repeated and/or prolonged procedures difficult. Ultimately, SSCs could preserve patients posterior dentition (Ettinger et al., 1998) due to their affordability since the only other affordable alternative might in fact be extraction. (d) Persons with Limited Finances or Dental Coverage There are many individuals who require extensive dental care but who have limited finances, no dental insurance, and/or are receiving social assistance. Limited Finances: Statistics Canada s most recent census report from 2011, classified 8.8% or 2.96 million Canadians as low-income individuals (Statistics Canada., 2011). Dental Insurance: The Canadian Health Measures Survey (CHMS) administered by Statistics Canada collected data from about 6,000 people in 15 communities selected randomly across Canada between March 2007 and February The sample statistically represents 97% of the

26 12 Canadian population aged six to seventy-nine years old. From this survey it was shown that 62% of Canadians had private dental insurance, and 6% had public insurance, while 32% did not have any dental insurance (Health Canada., 2010). Social Assistance: The Social Assistance Statistical Report (2010) administered by the Federal- Provincial-Territorial Directors of Income Support listed the number of families receiving social assistance between Between , the number of families that were recorded as receiving social assistance was as follows: a) Newfoundland and Labrador: 16,258 b) Prince Edward Island: 5,700 c) Nova Scotia: 24,836 d) New Brunswick: 31,500 e) Quebec: 884,330 f) Ontario: 372,000 g) Manitoba: 56,200 h) Saskatchewan: 41,700 i) Alberta: 49,400 j) British Columbia: 91,340 k) Yukon: 895

27 13 l) Northwest Territories: 1,859 m) Nunavut: 15,523 (Federal Provincial Territorial Directors of Income Support, 2010) Furthermore, according to the February 2014 Ontario Works Report, 450,552 individuals were listed as beneficiaries of Ontario Works Social Assistance (Ontario Ministry of Community and Social Services, 2014). These individuals may be unable to afford a laboratory-processed crown. Hence, the SSC restoration for the permanent posterior dentition could represent an effective, practical and affordable treatment option for these individuals (Ettinger et al., 1998). Whether placed as an interim or long-term restoration, the SSC could allow these patients to maintain their permanent posterior dentitions, preserve function and avoid dental extractions. 4. Methods Used in Previous Clinical Studies of Restorative Materials (a) Clinical Outcomes for Stainless Steel Crown Restorations The longevity of restorations is dependent on many factors including operator skill, materials used, the criteria for repair or replacement, and patient compliance (Miyamoto et al., 2007). Based on the current literature, it is difficult to draw specific conclusions relating to restoration longevity due to a lack of standardization. Definitions of restoration outcomes and various methodological designs remain as the most substantial differences found between studies (De Backer et al., 2007). In addition, there is a paucity of literature comparing the outcomes of SSC restorations to direct conventional restorations in the permanent posterior dentition.

28 14 In a prospective study, Roberts and Sherriff (1990) reported the survival of amalgam and SSC restorations placed in both primary and permanent posterior teeth over a 10-year period. This was one of the only clinical studies that traced and compared clinical outcomes of permanent molar SSCs versus other restorations (e.g. Class I and II amalgam restorations). The status of each restoration was recorded as: satisfactory, satisfactory but extracted for orthodontic purposes, failed, or exfoliated with a satisfactory restoration at the last visit. Failure of amalgam restorations was recorded if replacement was required. The main reasons for replacement and resultant failure classification included ditching, fractured filling or tooth, recurrent caries and new caries at other sites. If caries was observed at a site not associated with the original restoration but necessitating its replacement, this was classified as a false failure (i.e. the failure was unrelated to any problems with the original restoration). For SSC restorations, true failures were defined as when the crown became uncemented or demonstrated occlusal perforation. There was no mention or account for other potential modes of failure of the SSC restorations such as recurrent caries or tooth fracture (Roberts and Sherriff, 1990). A total of 468 SSCs placed in primary posterior teeth were evaluated. It was found that within this cohort, three had cement failure, and seven had occlusal perforation failure. Comparatively, of the 43 SSCs on permanent posterior teeth, only one true failure was reported (occlusal perforation) (Roberts and Sherriff, 1990). Despite the small sample size, this study can provide insight with regard to the possibility that there could be differences in outcomes for SSCs placed on permanent versus primary teeth. For evaluation of the SSC restoration in the permanent dentition the scope of outcomes should be broadened in comparison to the criteria reported previously in order to attain greater knowledge regarding the precise fate of this type of restoration.

29 15 Prior to 1990, several studies compared the longevity of preformed metal crowns to direct restorations in the posterior primary dentition and shared the same definitions for failure as outlined above. In one of the earliest studies, SSCs were compared with multisurface amalgam restorations placed in the same patients (Braff, 1975). Braff et al. (1975) evaluated seventy-six SSCs and 150 amalgam restorations over a 32-month period. Of these, there were 131 (87%) true amalgam restoration failures, and 19 (25%) true SSC failures (Braff, 1975). Dawson et al. and Eriksson et al. published similar studies in 1981 and 1988 respectively, comparing amalgam and SSC restorations in primary molar teeth (Dawson et al., 1981; Eriksson et al., 1988). Dawson et al. (1981) followed 114 patient records over a minimum of 2 years, comparing 114 Class I and 102 Class II amalgam restorations with 64 SSCs in primary molar teeth. It was reported that 37% of Class I and 71% of Class II amalgam restorations were replaced, as compared with only 13% of the SSCs (Dawson et al., 1981). Eriksson et al., (1988) evaluated 104 SSC teeth paired with antimere controls to exfoliation. Twenty-two of the SSC teeth (21%), and 66 of the 80 amalgamrestored teeth (83%) required further treatment (Eriksson et al., 1988). For each of these studies, a true failure was considered to occur when the crown or restoration was involved directly in the failure, whereas a false failure was the result from a cause remote from the restoration (Braff, 1975). The finding of recurrent caries was limited to amalgam restorations and was not considered during the assessment or account of failure for the SSC restorations. As such, occlusal perforation and loss of crown were considered as true failures. In 1996, Einwag and Dunninger modified their definition of restoration failure in a retrospective evaluation of paired SSCs and 2-surface amalgams of the primary dentition in 66 patients over 8 years. Each patient received one SSC and a 2-surface amalgam restoration, with each patient serving as their own internal control. Survival was defined as the restoration remaining in situ

30 16 without modification during the entire period of observation. Therefore, failure was recorded as a restoration requiring any repair or replacement (Einwag and Dunninger, 1996). The eight-year survival rate for the SSC restorations was 83% whereas after 4.5 years, the amalgam restorations had a survival rate well below 40%. The difference in replacement rate between the two forms of treatment was also significant. Only 4 of the 66 SSCs (6%) required replacement as compared to the 38 of 66 (58%) amalgam restorations. The most frequent reasons for the replacement of restorations were secondary to defects and new carious lesions (Einwag and Dunninger, 1996). Sharaf and Farsi (2004) was one of the first studies to not classify a repaired SSC (i.e. occlusal perforation with amalgam restoration) as a failure, and placed greater importance on the preservation and maintenance of the tooth. In their retrospective chart review, patient demographic data and the life span of SSCs in the primary posterior dentition were collected. The longevity of the SSC restoration was measured by the duration of time that the SSC was present on the primary tooth as viewed from the patient records. This measurement of duration would be appropriate for the evaluation of SSCs in the permanent dentition, as the goal is to maintain the existing tooth with as little intervention as possible. In 2005, Roberts et al. conducted a prospective study where posterior restorations in primary molars were assessed. True failures were defined as: recurrent caries, restoration fracture, marginal degradation, pulpal infection, and partial or total loss of the restoration. False failures were defined as those not directly related to the restoration itself, but that still necessitated the replacement of the observed restoration. For SSC restorations, true failures were defined as either crown loss or occlusal perforation, and false failures related to the failure of pulp treatments. From the Roberts et al. study (2005), the outcomes of 544 Class I, and 962 Class II resin-modified glass ionomer cement (RMGIC) restorations were compared to 1010 SSCs over a

31 17 seven year follow up. At the last review of each restoration, 98.3% of Class I, 97.3% of Class II RMGICs and 97.0% of SSCs were either satisfactory or withdrawn intact. Thirty (3%) SSC restorations were classified as true failures with occlusal perforation accounting for 21 cases and cement failure accounting for the remaining nine. Within the RMGIC true failure group, 1.7% for Class I and 2.7% for Class II restorations was reported, new and recurrent carious lesions accounted for the majority (73.0%) of replacements. The high success of the RMGIC restorations was due to their use being restricted to the treatment of minimal sized carious lesions. Whereas, SSCs were used to treat larger carious lesions, or where the decay process involved both proximal surfaces (Roberts et al., 2005). (b) Clinical Outcomes for Multisurface Intra Coronal Direct Restorations Soncini et al. (2007) conducted a randomized clinical trial to compare the replacement rates of amalgam and composite resin materials in children s posterior teeth over a 5-year period. Three overall categories of failure were used; restorative, extraction, and other. Restorative failure was described as dental caries and/or fracture of the tooth or restoration requiring replacement. Extraction was categorized as either the result of dental caries and/or fracture or as a result of periodontal problems requiring extraction. Lastly, any other failure was described as a failure not covered above requiring re-treatment of the involved tooth with a more extensive restoration. Within a group of 399 children, 509 amalgam and 753 composite restorations (CR) were placed in posterior permanent teeth. Over the 5-year period of observation, the frequency for restoration replacement or repair was higher for CR (14.9% and 2.8% respectively), as compared to the replacement or repair frequency for amalgam restorations (10.8% and 0.4% respectively). There was no statistically significant difference in the incidence of specific reasons for replacement on

32 18 the basis of the restorative material used (Soncini et al., 2007). Simecek et al. (2009) evaluated amalgam and composite resin restorations of the posterior permanent dentition based on more specific definitions. All restorations were recorded as either clinically acceptable or requiring replacement. Replacement was defined as re-treatment documented during the initial or periodic examination due to new or recurrent caries, defective restorations, or endodontic therapy. Replacement was further sub-classified if limited to the previously restored surfaces, as replacement of existing restorations (RERs). The date of replacement was documented as the date of the dental examination at which the need for retreatment had been documented. The time to replacement was recorded as the number of days from the initial examination to the examination documenting the need for replacement. Including initial and follow-up examinations, a total of 356 (31.2%) of 1,140 CR restorations required replacement, while 1,730 (27.3%) of 6,341 amalgam restorations required replacement. Of the restorations that had surfaces requiring treatment, further analyses revealed 5.8% of 5,307 amalgam restorations and 8.5% of 925 CR restorations were replaced due to recurrent caries or other factors limited to only the previously restored surfaces. Data available from the dental records neither allowed for determination of reason for replacement nor provided information relating to the time of initial restoration placement. This was regarded as a study limitation as reasons for replacement and restoration longevity could not be assessed (Simecek et al., 2009). Opdam et al. in 2007 and 2010 conducted retrospective studies comparing the longevity of amalgam and composite resin restorations of posterior permanent teeth. The two studies shared common definitions for outcomes regarding success and failure. Restoration failure was defined as when a restoration was either scheduled for replacement, replaced, repaired or when the tooth was extracted. Date and reason for failure was recorded from all patient charts. Success was

33 19 defined as when a restoration was still in function at the last check-up and found to be clinically acceptable. From the 2007 study, which evaluated Class I and II amalgam and composite resin restorations between 1990 and 1997; 182 (20%) of the 912 amalgam restorations and 259 (13.2%) of the 1955 CR restorations failed and required replacement. Reasons for failure were recorded for each restoration and caries accounted for the majority of the total failures (29% of amalgam and 38% of CR restorations). Life tables calculated from the data demonstrated a survival for CR restorations of 91.7% at 5 years and 82.2% at 10 years. While the survival for amalgam restorations was reported as 89.6% at 5 years and 79.2% at 10 years, demonstrating similar longevity. Limitations of this study included the operator s reliance on tongue shields with cotton rolls for moisture isolation and the lack of independent evaluation of restoration quality (Opdam et al., 2007). In the latter study by Opdam et al. (2010), 24% of the 1202 amalgam and 15% of the 747 CR Class II restorations were regarded as failures between 1983 and Recurrent caries was the main reason for failure (5.7% of amalgam, 6.6% of CR restorations) (Opdam et al., 2010). The final outcomes reported in both of the aforementioned studies were quite similar suggesting, among other things, that in all likelihood, the definitions used for restoration failure were consistent, and can be used reliably to study the longevity of any particular restoration. (c) Lab Fabricated Crown Clinical Outcomes As stated previously, there is a lack of literature that compares the longevity of multisurface intra coronal direct conventional restorations to SSCs in the permanent dentition. In place of the SSC restoration, literature was examined which included the use of cast full metal lab fabricated crowns (FMC) for the restoration of the posterior permanent dentition compared to conventional

34 20 restorative materials (e.g. amalgam, composite resin, ceramic and lab fabricated crowns, etc.). Van Nieuwenhuysen et al. (2003) conducted a long-term evaluation of large restorations in the permanent dentition in which 60% of the teeth had been treated endodontically. In all, 722 amalgam restorations, 115 composite resin restorations and 89 full gold metal crowns were placed in 428 adults. Restorations were classified as being in function, censored, or failed if they were repaired, replaced or indicated for extraction. Failures were classified further as being relative or absolute. Relative failure applied if the restoration was repaired once, while absolute failure applied if; a restoration had been repaired twice, the restoration or crown had been replaced or if the tooth had been extracted. Failures occurred in 28% of the amalgam restorations, 30% of the CR restorations and 24% of the FMC. From the total restorations, the most frequent reasons for failure included fracture of restoration (8%), recurrent caries (6%) and fracture of the tooth cusp (5%). In regards to failures for FMCs, the main reasons were secondary caries (7/21) and endodontic problems (6/21). Kaplan-Meier median survival times (where any re-treatment was considered as a failure) were calculated; amalgam restorations survived for 12.8 years, CR restorations survived for 7.8, and crown restorations survived for more than 14.6 years (Van Nieuwenhuysen et al., 2003). De Backer et al. in 2006 investigated the survival of full metal and porcelain fused to metal (PFM) crowns in relation to biologic and technical variables. Failures were divided and documented as being either biologic or technical/patient related. The failures were subdivided further as being either reversible or irreversible in nature. Biologic failures included; caries, periodontal problems, fracture of coronal structure, endodontic problems. Technical or patientrelated failure included; fracture of porcelain, loss of retention, trauma. Irreversible failure was defined having occurred when the full crown or tooth was lost, whereas reversible failure was

35 21 defined as having occurred when the crown required recementation. In a sample of 456 patients, 1036 full crowns (cast gold or PFM) were evaluated over a sample period of 18-years. Irreversible failure resulting in full crown or tooth loss occurred in 116 of the restored teeth. Biologic failures accounted for 66.4% of the irreversible failures, including caries (24.3%), periodontal problems (17.2%), fracture of the abutment tooth (12.9%), and endodontic problems (12.0%). Technical or patient-related failures, such as fracture of the porcelain or loss of retention accounted for the remainder of the overall failures. In a group of surviving restorations, 4.7% (43/920) experienced a reversible complication, indicating that there was a loss of retention and/or caries or pulpal problems, but the full crown could be recemented without failure of the tooth or full crown. Lastly, the reported Kaplan-Meier survival rate after 18 years was 80.3% and 78.6% for restored molars and premolars, respectively (De Backer et al., 2007). In 2007, Pjetursson et al. conducted a meta-analysis assessing the 5-year survival rates of allceramic single crowns as compared to PFM crowns with analysis of observed complications. Survival was defined as the crown remaining in situ with or without modification during the entire observation period. The analysis of the biological complications encompassed caries, loss of pulp vitality, tooth fracture and periodontal disease progression. Technical complications included; fracture or chipping of the ceramic, marginal gap/discoloration, and loss of retention. A total of 34 studies published since 1991 were included in the meta-analysis. For all-ceramic crowns, 27 studies provided data on the survival of a total of 6006 crowns after a mean follow-up time of 4.9 years. Four hundred and thirty crowns were reported as lost, translating to a 5-year survival of 93.3%. For PFM, 6 studies provided data on the survival of a total of 1765 crowns, to which 160 crowns were reported as lost, translating into a 5-year survival of 95.6%. The most frequent biological complication of all-ceramic crowns was; loss of pulp vitality, annual

36 22 complication rate of 0.43%, and caries, annual complication rate of 0.37% and 0.64% for PFM (Pjetursson et al., 2007). 5) Radiographic Evaluation and Outcomes There are few studies that include longitudinal radiographic examination of restorations placed as part of their evaluation of longevity and outcomes (Knoernschild and Campbell, 2000). As an adjunct to clinical evaluation, radiographic examination can provide important diagnostic information pertaining to; new or recurrent carious lesions, pulpal status, apical or periradicular disease, and periodontal status (White and Pharoah, 2009). (a) Pulpal Status Clinical signs of pulpal or periapical inflammation are variable in nature (Orstavik et al., 1986). With no known blood or salivary parameters, radiographic interpretation is the dominant criterion for the diagnosis, and assessment of progression or resolution of periapical inflammation and/or apical periodontitis often referred to as rarefying osteitis (Federation Dentaire Internationale, 1982; Orstavik et al., 1986). Apical periodontitis is primarily an inflammatory reaction to dental caries caused by infection of the dental pulp and root canal system (Ridao-Sacie et al., 2007). Necrotic and infected pulps may cause the development of gradually increasing, inflammatory lesions of the periapical tissues (Simon, 1984), accompanied by structural derangement of the surrounding bone (Valderhaug, 1972). These changes may include a widened periodontal ligament space, loss of lamina dura, and apical/periradicular radiolucency (referred to above as rarefying osteitis, which reflects a degree of non-specificity relating to the actual underlying biological processes being imaged).

37 23 Orstavik (1986) described periapical inflammation as a process that follows a biological continuum and may change direction into either healing or destructive phases (Orstavik et al., 1986). Through understanding of this continuum, Orstavik (1986) applied an ordinal scale scoring system to the radiographic evaluations of apical periodontitis and developed the widely utilized, Periapical Index (PAI) scoring system (Orstavik et al., 1986). The PAI utilizes an ordinal scale consisting of five scores designed to determine the absence, presence, or transformation of a disease state (Orstavik et al., 1986; Trope et al., 1999). The PAI is based on reference radiographs with corresponding line drawings and their associated score on a photographic print, which is useful for calibration and training of investigators. These scores are based on correlation with verified histological diagnoses published originally by Brynolf (Brynolf, 1967). Using the PAI score, the periapical status of each of the tooth roots is categorized and given a designated score between 1 and 5. The five categories include; (1) Normal periapical structure; (2) Small changes in bone structure; (3) Changes in bone structure with some mineral loss; (4) Periodontitis with well-defined radiolucent area; and (5) Severe periodontitis with exacerbating features (Ridao-Sacie et al., 2007). Each category used in the PAI represents a step on an ordinal scale of registration of periapical infection. The worst score of all roots is to be taken to represent the PAI score for multirooted teeth. As reported throughout the endodontic literature, a PAI score of 1-2 is commonly regarded as healthy, healed or minimally inflamed, whereas a score of 3-5 is diseased (Kerosuo and Orstavik, 1997; Orstavik et al., 1986; Ridao-Sacie et al., 2007; Trope et al., 1999).

38 24 (b) Periodontal Status Radiographs play an integral role in the assessment of periodontal disease and associated alveolar bone loss. They provide unique information about the status of the periodontium and a permanent record of the condition of the bone throughout the course of the disease. Radiographs aid the clinician in identifying the extent of destruction of alveolar bone, local contributing factors, and features of the periodontium that influence the prognosis. Important features related to periodontal status that may be identified radiographically include: amount of bone present, condition of the alveolar crests, bone loss in furcation areas, width of the periodontal ligament space, local irritating factors that increase the risk of periodontal disease (i.e. calculus or overextended restorations), root length and morphology, open interproximal contacts, anatomic considerations, and/or pathologic considerations (i.e. caries, periapical lesions, root resorption) (White and Pharoah, 2009). Radiographic assessment alone cannot be relied upon to make a definitive diagnosis relating to the absence, presence or activity of periodontal disease. But in the context of most investigations that are not focused entirely on periodontitis as an outcome, this method of assessment is acceptable. In the primary dentition, alveolar bone loss (and proximal caries) has not been correlated directly to the degree of success or failure associated with preformed SSCs (Bimstein et al., 1996). Sharaf et al. (2004) conducted one of the only studies to evaluate clinically and radiographically, the effect of SSCs placed on primary molars on the surrounding gingival and bone structures. Bitewing radiographs were utilized using standardized angulation of the X-ray cone to generate clear images of the cemento-enamel junction (CEJ) and alveolar bone crest between the primary molars. As described in the literature previously, interproximal bone level was considered normal or non-resorbed when the distance between the crest of interdental bone and the CEJ was

39 25 2mm or less. When the distance was more than 2mm, the bone was considered resorbed (Bimstein et al., 1988; Bimstein and Garcia-Godoy, 1994; Bimstein et al., 1993; Bimstein et al., 1996). Quality of the crown was also evaluated and recorded as either adequate when all the margins were smooth and well adapted covering all dentin, or inadequate, when crown margins appeared too short, extended below the CEJ or away from the tooth surface by more than 1mm (Sharaf and Farsi, 2004). The findings from this study coincided with previously published work (Bimstein, 1992; Bimstein et al., 1988; Bimstein et al., 1993) confirming that interproximal bone resorption was not significantly affected by crown marginal extension or adaptation, preservation of tight proximal contacts between teeth, or duration of presence of the crown. However, from the crowns that demonstrated interproximal bone resorption; crowns that were judged radiographically as inadequate (19/26, 73.1%) were more likely to demonstrate resorption compared to those that were adequate (76/228, 33.3%) (Sharaf and Farsi, 2004). Most recently, Belduz and Yilmaz (2014) conducted a randomized, controlled clinical trial to evaluate the gingival and periodontal health of restored posterior primary molars with traditional and esthetic SSC restorations. Two hundred fifteen crowns were placed, with each child receiving one traditional SSC (77) and one randomly selected esthetic crown (45 open-faced SSC, 44 veneered-ssc, 29 NuSmile pre-veneered SSC, 20 PedoPearls aluminum veneered crowns). The oral hygiene and periodontal health of the restored teeth were evaluated clinically and radiographically at three and six month intervals for 18 months. Similar to previously published studies (Bimstein, 1992; Bimstein et al., 1988; Bimstein et al., 1993; Bimstein et al., 1996; Sharaf and Farsi, 2004) the interproximal bone level was considered normal and not resorbed when the distance between the crest of interdental bone and CEJ was less than 2mm.

40 26 Bone was considered resorbed when this distance was more than 2mm. The radiographic results were not published, however, the clinical probing pocket depths revealed all SSC except for PedoPearls at 18 months (1.76 +/- 0.64) to be less than 2mm. To date, there has been no study that has investigated the effects of SSC restorations placed on the permanent dentition and alveolar bone levels by way of radiographic assessment. However, the measurement and evaluation of bone loss for the permanent dentition as defined by White et al., (2009) coincides with the criteria used by Sharaf et al. (2004) in the primary dentition. By definition, alveolar bone loss is when the crest of the buccal and lingual cortical plates and the intervening interdental bone has been resorbed with the subsequent apical positioning of the crest of alveolar bone from the CEJ. Mild bone loss may be defined as approximately a 1-2mm loss of the supporting bone, and moderate loss is anything greater than 2mm up to the loss of half the supporting bone height. Severe loss is anything beyond this point (White and Pharoah, 2009). Knoernschild and Campbell (2000) conducted a review of the literature regarding periodontal health surrounding fixed lab fabricated full coronal restorations in the permanent dentition. From the available literature, attachment loss was determined by changes noted in either periodontal probing depths or radiographic alveolar bone height evaluated independently or in conjunction. To date, the most precise measurement of alveolar bone loss is through the use of intra-oral radiographs that can permit measurement of changes as small as 0.2mm (Benn, 1990). Despite accuracy of measurement, the studies examined by Knoernschild and Campbell, did not report their methodology in great detail. As such, the radiographic measurements documented were presumed to be recorded interproximally from the radiographic crown margin to alveolar bone crest (Knoernschild and Campbell, 2000).

41 27 6. Purpose of the Study The prefabricated full coverage SSC has proven to be extremely durable, relatively inexpensive and available for the restoration of both primary and permanent dentitions (Randall, 2002; Seale, 2002). Each of these attributes has contributed to the success and recognition of the SSC as the most effective primary molar restoration (Kindelan et al., 2008). Indications for the use of SSCs include but are not limited to the restoration of multisurface caries, teeth with developmental enamel or dentinal defects, teeth with traumatic fracture or extensive wear, and persons with special needs, or those who are uncooperative and require the use of GA (Brook and King, 1982; Croll, 1993; M. S. Duggal and Curzon, 1989; Goldberg, 1969; Titley and Farkouh, 2001). The available literature concerning the outcomes and longevity of SSC restorations has largely been limited to the primary dentition. Roberts and Sherriff (1990) was one of the few studies that evaluated permanent molar SSCs with amalgam restorations, and revealed only 2.3% of the SSCs required replacement over a 10-year period. The promising results from this study in combination with the emerging potential application for SSC restorations for the permanent dentition represent an important treatment option for several patient populations. These include: persons with special needs, persons requiring use of general anesthetic, geriatric populations and those with limited finances or dental coverage. The longevity of restorations is dependent on many factors including operator skills, materials used, the criteria for repair or replacement, and patient compliance (Miyamoto et al., 2007). Based on the current literature, it remains difficult to draw specific conclusions relating to restoration longevity due to a lack of standardization. Definitions of restoration outcomes and various methodological designs remain as the most substantial differences found between studies (De Backer et al., 2007). In addition, there was a paucity of literature comparing the outcomes of SSC restorations to direct conventional

42 28 multisurface restorations in permanent posterior teeth. For these reasons, the purpose of this retrospective cohort study was to evaluate the long-term clinical and radiographic outcomes of SSC restorations in the posterior permanent dentition.

43 29 B. EXPECTED OUTCOMES 1. A stainless steel crown restoration is an effective long-term restoration for the permanent posterior dentition. 2. A stainless steel crown restoration on a permanent posterior tooth has a better or equal outcome (success/failure) compared to other commonly used multisurface restorative materials. 3. Posterior permanent teeth restored with a stainless steel crown restoration will have minimal (<2mm) alveolar bone loss and demonstrate pulpal health as measured by PAI scores.

44 30 C. AIMS AND OBJECTIVES 1) To assess the long-term clinical and radiographic outcomes of SSC restorations on the permanent posterior dentition. 2) To evaluate if SSCs in the posterior permanent dentition have superior longevity as compared to the other restorative treatments. 3) To assess the degree of alveolar bone loss surrounding the SSC restoration radiographically thereby indirectly determining the effects on the periodontium. 4) To assess the pulpal status of posterior permanent teeth radiographically before and after receiving a SSC restoration.

45 31 D. MATERIALS AND METHODS This retrospective cohort study was approved by Mount Sinai Hospital s Research Ethics Board (REB: CV) and supported by the Associate Dean of Graduate Studies, Faculty of Dentistry, as having scientific merit. As per Mount Sinai Hospital s REB recommendations, specific patient consent was not required to conduct this low risk chart review study. 1. Sample The subjects for this study included registered patients at the Mount Sinai Hospital s (MSH) Dentistry Clinic for Persons with Special Needs. The MSH Dentistry Clinic is located within a tertiary/quaternary care hospital and is designed to provide all forms of dental care for a diverse population of persons with clearly identified disabilities. The patients registered in the MSH Clinic must be referred by a primary care physician, dental practitioner, primary caregiver or support worker, and are commonly 16 years of age or older. The Clinic is located within a hospital setting in order to facilitate medical management and as needed, provide care for patients under sedation or general anesthesia (S Hulland, 1997; S. Hulland and Sigal, 2000; Sigal and Sigal, 2006). The inclusion criteria included active patients with at least one SSC restoration of their permanent posterior dentitions. From these patients, all conventional restorations of their permanent posterior dentitions whether previously placed from a different center or at the MSH Clinic were assessed. Conventional multisurface restorations included amalgam, composite resin or glass ionomer. Restorative treatments at the MSH Clinic may have been conducted either in the clinic under local anesthesia or in the operating room under GA. Any patient without a

46 32 history of a SSC restoration as documented within their MSH chart was excluded from the study. 2. Data Collection The primary investigator (AS) conducted a comprehensive chart review of all current charts registered within the MSH Dentistry Clinic for Persons with Special Needs. Administrative AbelDent Software from the MSH Dentistry Clinic was used to conduct a search of all patients since 1994 that received a billing code for a SSC restoration. These recorded billing dates were used to expedite the collection of dental treatment data from the respective dental charts. (a) Part 1: Demographic and Dental Information Collection Microsoft Visual Studio Express 2013 was used to create a unique and secure, passwordprotected electronic database for data collection. Each patient was assigned a research code to protect his or her identity. The demographic, clinical evaluation and outcome assessments of each respective posterior permanent dentition restoration were provided based upon chart entries. All possible input outcomes were assigned respective variables to simplify data collection and future analyses. The information that was collected included the following: i) Appendix 1: Demographics (Pages ) a) Patient demographics; medical records number, date of birth, gender, date of initial visit to MSH, and of most recent visit, referral source to MSH, type of residence b) Family History; history of medical issues c) Medical Information; medical diagnoses, review of systems, allergies, surgeries

47 33 d) Medications Prescribed e) Previous Surgical Experience; number of dental general anesthetics, number of teeth recorded at each treatment date f) Dental Information; dental coverage, findings from initial exam (occlusion, overbite, overjet, parafunction), caries risk, oral hygiene (OH) status, number of teeth present, what, where and how dental treatment was conducted, who performed the treatment, recall frequency and cooperation/behavioural problems. The American Academy of Pediatric Dentistry caries risk assessment tool (CAT) was the foundation of recorded entries for patient s caries risk (American Academy Pediatric Dentistry, 2013). ii) Appendix 2: Dental Treatment (Pages ) For each restored permanent posterior tooth the following information was collected in a temporal fashion from time of placement or new patient exam (for pre-existing restorations) to date of most recent patient visit: tooth number, date of initial new patient exam, final assessment or date of treatment, dental diagnoses, tooth surfaces restored, type of restorative treatment, anesthetic method, status of pre-existing restoration and final assessment of restoration. For each restoration entry, the possible dental diagnoses as documented from the chart records included one the following ten options: i) Caries: Carious lesion and associated surfaces that required dental treatment.

48 34 ii) Pre-existing Restoration: For conventional restorations (amalgam, composite resin, and glass ionomer) present at new patient exam where previous dental history was unknown, or at final assessment. iii) Pre-existing SSC: For stainless steel crown restorations present at new patient exam where previous dental history was unknown, or at final assessment. iv) Loose/Lost Restoration: Conventional restoration (amalgam, composite resin, glass ionomer) documented as loose or missing. v) Loose/Lost SSC: Stainless steel crown documented as loose, having inadequate adaptation or missing. vi) SSC Perforation: Stainless steel crown with localized occlusal crown perforation. vii) Tooth Fracture: Loss of tooth structure (partial/complete) and associated surfaces. viii) Restoration Fracture: Loss of conventional restoration structure (partial/complete) and associated surfaces. ix) Pulpal Disease/Necrosis: Recorded as having possible history of pain, stimulated or spontaneous, diagnosed as irreversible pulpitis or pulpal necrosis, and possible evidence of fistula, parulis, abscess and/or facial swelling. x) Periodontal disease: When treatment was conducted without diagnoses of caries, tooth or restoration fracture, pulpal pathology or necrosis. This included periodontal disease associated with significant tooth mobility.

49 35 The collection of patient demographic and dental diagnoses was conducted as outlined in Appendices 1 and 2, which was adapted from Hulland, S., (1997) (S. Hulland and Sigal, 2000; Sigal and Sigal, 2006). Based on the reviewed literature regarding the assessment of restoration outcomes, the following criteria were applied when assessing and recording each posterior permanent restoration and the status of the pre-existing restoration: i) Unknown: For pre-existing restorations where previous dental history was not known. ii) Intact or within normal limits: The restoration was present and did not require any adjustment or treatment. iii) Non-restored (virgin) tooth: The restoration recorded was the first treatment for the respective tooth. iv) New/Original Site: An additional restoration was placed on the noted tooth, involving a different surface(s) from that previously restored. v) Defect (monitored with no treatment required): The restoration was present with a localized minor defect that did not pose any added cariogenic or traumatic risk. The restoration was monitored and did not require adjustment or treatment. vi) Requiring repair: The restoration was present with a localized defect that presented as a cariogenic or traumatic risk factor. The defect within the existing restoration was repaired. vii) Requiring recementation: Applicable only to the SSC restoration. The SSC restoration was intact but with inadequate retention. Utilizing the same SSC, it was removed, the respective tooth

50 36 was within normal limits, and the SSC was re-adapted and cemented. This was further classified as a restoration failure. viii) Requiring replacement: The restoration was present with a severe defect, fracture, and/or loss of retention. The restoration was replaced utilizing the same type and extent of restorative treatment (SSC, Amalgam, Composite Resin, and GI). This was further classified as a restoration failure. ix) Failure: The restoration may or may not have been present due to a severe defect, recurrent or new carious lesion, fracture, and/or loss of retention. Treatment required may have included endodontic therapy, placement of a larger and/or different restoration, new SSC, SSC recementation, or extraction. For conventional restorative treatments (Amalgam, Composite Resin, and Glass Ionomer) replacement of a restoration utilizing the same material of same or greater extent, was defined as a failure of the initial restoration. vi) Restoration Chronology The history of health and/or treatment for each restored posterior permanent tooth was recorded over time. Pre-existing restorations present at time of new patient exam were recorded as the date of the initial exam (censored). The date of the restoration requiring repair, replacement, recementation, or failure was documented as the date the treatment was conducted.

51 37 The duration of function or survival was recorded as the number of years between the following start and end time points: a) Start: Either the date of initial exam for preexisting restorations (censored), or the date of placement for new restorations b) End: Either the most recent examination documenting the intact restoration (censored), or the date of restoration failure If at the final assessment (most recent examination) the restoration was deemed as requiring further treatment, this was recorded as a failure for the respective date. In the event that a tooth was lost between recall exams, the first date at which the tooth was observed as still present was recorded as the terminal survival date. These evaluations allowed for comparisons to be made regarding the outcomes and longevity between SSC and conventional restorations of the posterior permanent dentition. (b) Part 2: Radiographic Assessment of SSC Restorations Radiographic assessments of the SSC restorations were made through the examination of bitewing and periapical radiographs where available. It should be noted that due to poor cooperation, all active patients at the MSH Dentistry Clinic did not have diagnostic radiographs available for analysis. Further, some patients whom required diagnoses and treatment under GA had a limited number of radiographs, as these were dependent on their frequency of GA procedures.

52 38 For the radiographs available, the method of digitizing the radiographic images was standardized; films were mounted in a cardboard slot to block off ambient light emanating from the illuminated view box, a ten-inch copy stand secured and directed the Canon G12 digital camera 5.7cm over the mounted radiograph. The camera had the following settings: ISO 200, Macro, Aperture value of 5.6, No flash, Zoom (5-50cm), and with Daylight capture. The images were saved as JPEG files with a respective research code to protect the patient s identity. These images were then uploaded into the secure, password-protected electronic database for collection and analyses (Page 167). From these records, posterior radiographs in which the proximal areas were acceptable for inclusion had minimal distortion, minimal overlapping between proximal surfaces, and demonstrated a clear image of the alveolar bone crest (AB) and cementoenamel junction. All radiographs meeting inclusion criteria were read digitally on a 10 Hewlett-Packard computer screen and a measurement of the distance from the AB to the CEJ was recorded within the database utilizing an electronic measuring tool. To control for magnification, the JPEG files that were uploaded into the unique database were automatically set into a standardized viewing box for size 2 films. Adapted by Bimstein et al., 1988 & 1996 and Sharaf et al., 2003, interproximal bone level was considered normal or non-resorbed if the distance between the crest of interdental bone and the CEJ was 2mm or less. If this distance was more than 2mm, the bone was considered resorbed. The observations were recorded over time allowing for the assessment of periodontal status surrounding the SSC restorations in the posterior permanent dentition. A subsample study population with before and after periapical radiographic images of the tooth

53 39 receiving the SSC restoration had both images analyzed. All digitized images were analyzed on a 10 Hewlett-Packard computer screen. The periapical status of the respective tooth was classified using the Periapical Index (PAI) Scoring Scale as described by Orstvik (1986) as follows: (1) = Normal periapical structure (healthy); (2) = Small changes in bone structure (mild inflammation/pdl widening); (3) = Changes in bone structure with some mineral loss; (4) = Periodontitis with well-defined radiolucent area; (5) = Severe periodontitis with exacerbating features. Reference radiographs and corresponding line drawings with their associated PAI scores as provided by Orstvik (1986) were utilized when assessing the digitized periapical radiographs (Orstavik et al., 1986). For multirooted posterior teeth, the worst score of all roots was taken to represent the PAI score. A PAI score of 1-2 was regarded as healthy or successful, whereas a score of 3-5 was regarded as a failure and diseased. The observations were recorded over time allowing for assessment of the pulpal status of SSC restored posterior permanent teeth. Prior to the review of active patient charts from the MSH Dentistry Clinic, two pilot trials were conducted. For the first pilot trial, the primary investigator (PI) was standardized with a senior dentist from the MSH Dentistry Clinic by independently reading charts from 10 randomly selected patients from the inactive archives. In the second pilot trial, the PI was standardized with a Periodontist and an Endodontist from the MSH Dentistry Clinic by independently assessing 10 randomly selected radiographs of SSC restorations from the inactive archives. Each

54 40 patient/radiograph was assigned a research code to protect his or her identity. Agreement analysis comparing transcription accuracy was conducted between the PI and senior experts to achieve standardization. All data was entered into the unique and secure, password-protected electronic database (Microsoft Visual Studio Express 2013) exported into Microsoft Excel software and SAS format for statistical analysis. Statistical analyses were carried out using SAS/STAT software version 9.2 for Windows (SAS Institute Inc.). 3. Data Analysis For continuous variables descriptive summaries were performed as medians with ranges (minmax). In case of comparable medians and means, the mean, standard error and ranges were reported. For analyses where each subject contributed only one observation, summary statistics were calculated in the usual manner. For cases where subjects contributed two or more observations, standard deviations were calculated by taking into account the clustered nature of the data. For binary and categorical variables, such as demographic, clinical and radiographic observations, the number and percent of observations in each category were computed. Agreement analyses were conducted between the PI and respective expert(s) from the pilot trials as a total percentage of matched correct findings from a list of 566 and 60 items, from pilot 1 and 2 respectively. Product-limit estimate of restoration longevities (some of which were censored) were summarized using the method of Kaplan and Meier (Kaplan, 1958), separately for SSC, AM and CR restorations. Standard errors and 95% confidence intervals were obtained using the method

55 41 of Williams (Williams, 1995), which adjusted for correlations between the multiple restoration longevities per subject. New and pre-existing restorations were analyzed separately. Longevity was calculated as the time from placement of the restoration until the earlier of the time it failed or the end of study. Restorations still in place at the conclusion of the study period were treated as right-censored. In the case of pre-existing restorations, the date of placement was not known, and date of first presentation at the MSH Dentistry Clinic was used as a surrogate. A further survival analysis of new and pre-existing restorations combined was conducted. In this analysis, all pre-existing restorations were treated as left-censored because their actual placement dates were unknown. Each of the three survival analyses (new, pre-existing, and combined) were conducted separately for SSC and AM restorations. For CR restorations, only the analysis for pre-existing restorations was conducted due to the paucity of newly placed CR restorations. For new restorations only, and for each type of restoration, subgroup longevity (survival) summaries were produced: gender (male, female); age at placement (0-22, 22-30, 30-40, 40+); restoration location (upper, lower); restoration location (right, left); restoration location (upper right, upper left, lower right, lower left). Crude success rates for new SSC and AM restorations were calculated with standard errors obtained using the method of Williams (Williams, 1995), which adjusted for correlations between the multiple restoration longevities per subject. The crude success rate was defined as the proportion of restorations that had not failed by the end of the study period.

56 42 E. RESULTS 1. Pilot Study Agreement Analysis and Standardization Chart review assessed independently by PI and senior dentist from the MSH Clinic revealed 557/566 matched items with a 98.4% agreement. Radiographic measurement and interpretation assessed independently by PI, endodontist and periodontist revealed 60/60 matched items with a 100.0% agreement (Page 171, Appendix 5). 2. Part 1: Patient Demographics and Dental Treatment Two hundred and seventy-one subjects (males = 160, females = 111) were included in this study with a median age of 44 years ( ) as of March 31 st, Median age for MSH new patient exam was 24.5 years ( ) and the median age for first new restoration conducted at MSH was 29.0 years ( ) [Page 81, Table 1 & Figure 1; Pages 82-83, Table 2 & Figures 2, 3, 4]. Mean time as an active patient documented from initial to most recent dental appointment was 11.9 (0.52) years with a range of years. (a) Medical History Individuals with cognitive impairment, developmental delay and mental retardation represented the largest groups within the current patient population, comprising 83%, 79% and 78% respectively. The other most frequently observed conditions in descending order were seizure disorder, physical impairment, attention deficit disorder/attention deficit hyperactivity

57 43 disorder/autism (unspecified), and autism (specified) [Page 84, Table 3; Page 88, Table 4]. Ninety seven percent of the patients had at least three disorders and 88% had four or more comorbid conditions/disorders [Page 88, Table 5]. At least one medication was being taken by 86.7% (235/271) of the patients with sixty percent taking psychotropic medications. The other most frequently observed prescribed medications included anticonvulsants (36%) and inhalers (12%) [Pages 89-90, Table 6 & Table 7]. The Ontario Disability Support Program (ODSP) supported nearly all of the patients in the study (96%) [Page 90, Table 8]. (b) Dental History From initial new patient exam, the record of patient s occlusion, overbite, and overjet were not readily documented and could not be analyzed. Parafunction/bruxism was recorded as a positive finding in 215 patients, representing 79%. The majority of patients were assessed as having high caries risk (65%) and had either fair or poor oral hygiene, 47% and 42% respectively. Two hundred and twenty two patients (82%) were seen on a 3-month recall frequency, with the remainder seen every 6 months [Page 91, Table 9]. (c) Behaviour Sixty-four percent of patients were reported as negative (29.9%) or definitely negative (34.7%) on the Frankl Scale of behaviour and cooperation [Page 92, Table 10]. A total number of 187 patients (69.0%) received at least one dental general anaesthetic.

58 44 (d) Dental Restorations The 271 patients in the study comprised 2623 posterior permanent dentition restorations, including 766 SSC, 1651 Amalgams, 204 Composite Resins, and 2 Glass Ionomers. The median number for all posterior restorations per subject was 9.0 with a range of It was more common for patients to have multiple amalgam restorations (median 6 as compared to 2 for SSC), and most teeth had a single restoration [Pages 93-95, Table 11 & Figures 5, 6, 7]. From total number of restorations for all subjects, amalgam restorations were the most commonly documented (62.9%), followed by SSC (29.2%) and composite resin (7.8%). There was a negligible amount of glass ionomer restorations (two) and did not allow for any analyses or interpretation [See Table 12 Below and Page 96 for Figure 8]. Restoration type All Restorations for All Subjects N (%) SSC Restorations only N (%) AM Restorations only N (%) CR Restorations only N (%) Composite resin 204 (7.8%) 204 (100.0%) Amalgam 1651 (62.9%) 1651 (100.0%) Stainless steel 766 (29.2%) 766 (100.0%) crown Glass ionomer 2 (0.1%) Notes: 1. The denominator for the 'All Restorations for All Subjects' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type Table 12 showing the number of restorations by type (composite resin, amalgam, stainless steel crown or glass ionomer) Tables 13 and 14 on pages demonstrated the distribution of restorations per subject by gender. No apparent differences were observed and consistent trends remained with more teeth having amalgam restorations as compared to SSC or composite resin. There was an equal distribution of restorations placed between arches and quadrants. Table 15 and Figures 9, 10, 11 on pages , showed the distribution of teeth treated by the various

59 45 restorative materials according to arch location. For the majority of all restoration types, the permanent first molar was the most commonly restored tooth in each quadrant of the mouth [Page , Table 16 & Figures 12, 13, 14, 15]. Tables 17 and 18 on pages demonstrated the distribution of restorations by tooth location and gender. The findings were consistent with that of the combined data mentioned above. From the 2621 restorations recorded, 1664 (63.5%) were placed at the MSH Clinic, including 650 SSC (84.9%), 1011 AM (61.2%) and 3 CR (1.5%). A total of 957 (36.5%) restorations were pre-existing at time of new patient exam, including 116 (15.1%) SSC, 640 (38.8%) AM and 201 (98.5%) CR [Page 107, Table 19]. From the new restoration records, caries was the most commonly recorded diagnoses for the placement of SSCs (86.0%) and AMs (98.0%). Tooth fracture was recorded as the other most frequently observed diagnosis for the placement of both SSC and AM restorations, 6.2% and 0.8% respectively [Page 108, Table 20]. (e) Failed Dental Restorations There were 883 failed restorations from the 2621 combined pre-existing and new restorations reported, including 120 (58.8%) CRs, 672 (40.7%) AMs and 91 (11.9%) SSCs [Page 107, Table 19; Page 109, Figure 16]. (i) Failed Dental Restorations: Stainless Steel Crowns The breakdown for SSC failures, included extraction (61.5%), replacement of SSC (36.3%), and SSC recementation (2.2%). Most common diagnoses for extraction of SSC restored teeth was

60 46 secondary to periodontal disease (44.6%), followed by pulpal pathology/necrosis (37.5%) and caries (14.3%) [See Table 21 Below]. Number and Percentage of SSC Failures Result of Reported Failure Number of Failures Percentage (/91) Recementation Replacement Extractions Diagnosis Provided for Given Failure Diagnoses for Reported SSC Failures Recementation Replacement Extraction Percentage Number of Percentage Number of (/91) Diagnoses (/91) Diagnoses Number of Diagnoses Table 21 showing the breakdown of diagnoses of SSC restoration recorded failures Table 22 below demonstrating the extraction of the 25 SSC restored teeth secondary to periodontal disease was from 15 patients. Similarly, the 37 amalgam restored teeth that were extracted due to periodontal disease was from 15 patients. Five of the fifteen patients had both SSC and amalgam restored teeth extracted secondary to periodontal disease. Percentage (/91) Caries Loose/Lost SSC SSC Perforation Pulpal pathology/ Necrosis Periodontal disease Total Number of SSC and AM Extractions from Periodontal Disease Recorded Per Patient 1 SSC 2 SSC 3 SSC 4 SSC 5 SSC 6 SSC 7 SSC Total (25 SSC) Number of Patients AM 2 AM 3 AM 4 AM 5 AM 6 AM 7 AM Total (37 AM) Number of Patients Table 22 showing the distribution of SSC and amalgam (AM) extractions secondary to periodontal disease per patient

61 47 There were 29 (3.8%) SSC occlusal perforations recorded, 12 were replaced with new SSCs and classified as failures. The remaining 17 received occlusal amalgam repairs and were not classified as failures of the SSCs, or as conventional amalgam restorations [Page 110, Table 23]. (ii) Failed Dental Restorations: Amalgam Restorations From the combined pre-existing and new AM restoration records, replacement of restoration 434/672 (64.6%) accounted for the most AM failures; with 259 (59.6%) replaced with SSCs, 49 (11.3%) and 126 (29.0%) replaced with AM restorations of same, and greater extent respectively. Table 24 on page 111 depicts the diagnoses for specific amalgam restoration failures that were replaced with new restorations. The remaining 35.4% of AM failures resulted in extractions. Caries was the primary diagnosis recorded in 78.4% of all documented AM restoration failures (57.1% for replacements and 21.3% for extractions). From the 238 teeth restored with AM that were extracted; 143 had caries, 38 had pulpal pathology/necrosis, 37 had periodontal disease, 1 had loose/lost restoration and 1 had restoration fracture [See Table 25 Below].

62 48 Result of Reported Failure Number and Percentage of AM Failures Percentage (Replacement & Extractions/672) (Replacement Material /434) Number of Failures Replacement With SSC With AM (Same Extent) With AM (Greater Extent) With CR With GI Extractions Total % Diagnosis Provided for Given Failure Diagnoses for Reported AM Failures Replacement Extraction Percentage Number of (/672) Diagnoses Number of Diagnoses Percentage (/672) Caries Loose/Lost Restoration Tooth Fracture Restoration Fracture Pre-existing restoration (Inadequate) Pre-existing SSC (Inadequate) Pulpal pathology/ Necrosis Periodontal disease Total Table 25 showing the breakdown and diagnoses of amalgam restoration failures (iii) Failed Dental Restorations: Composite Resin Restorations From the combined pre-existing and new CR restoration records, replacement of restoration 94/120 (78.3%) accounted for the most CR failures; with 57 (60.6%) replaced with SSCs, 35 (37.2%) and 2 (2.1%) replaced with AM and CR (same extent) restorations respectively. The remaining 21.7% of CR failures resulted in extractions. Caries was the most reported diagnosis

63 49 for all the documented CR restoration failures, accounting for 91.7% (74.2% for replacements and 17.5% for extractions). From the 26 teeth restored with CR that were extracted; 21 had caries, 3 had pulpal pathology/necrosis and 2 had tooth fracture [See Table 26 Below]. Table 27 on page 112 depicts the diagnoses for specific composite resin restoration failures that were replaced with new restorations. Result of Reported Failure Number and Percentage of CR Failures Percentage (Replacement & Extractions/120) (Replacement Material /94) Number of Failures Replacement With SSC With AM With CR (Same Extent) With CR (Greater Extent) 0 0 With GI 0 0 Extractions Total Diagnosis Provided for Given Failure Diagnoses for Reported CR Failures Replacement Extraction Percentage Number of (/120) Diagnoses Number of Diagnoses Percentage (/120) Caries Loose/Lost Restoration Tooth Fracture Restoration Fracture Pre-existing restoration (Inadequate) Pre-existing SSC (Inadequate) Pulpal pathology/ Necrosis Periodontal disease Total Table 26 showing the breakdown and diagnoses of all composite resin restoration failures

64 50 (iv) Failed Dental Restorations: New versus Pre-Existing From the 650 SSC restorations placed, 70 (10.8%) failures were reported, and from the 1011 AM restorations placed, 372 (36.8%) failures were reported [Page , Table 28 & Figure 17]. From the pre-existing restorations records, 21/116 (18.1%) SSC, 300/640 (46.9%) AM and 119/201 (59.2%) CR restorations failed during patient follow up [Pages , Table 29 & Figure 18]. (v) Summary Table Number and Percentage of Failures Result of Reported Failure SSC Number of Failures (%) Amalgam Number of Failures (%) Composite Resin Number of Failures (%) Recementation 2 (2.2) 0 (0.0) 0 (0.0) Replacement (Total) 33 (36.3) 434 (64.6) 94 (78.3) With SSC 33 (36.3) 259 (38.5) 57 (47.5) With Amalgam (Same 0 (0.0) 49 (7.4) 35 (29.1) Extent) With Amalgam (Greater 0 (0.0) 126 (18.7) 2 (1.7) Extent) With Composite Resin 0 (0.0) 0 (0.0) 0 (0.0) Extractions 56 (61.5) 238 (35.4) 26 (21.7) Table 30: Summary of Failed Dental Restorations (f) Ten Year Survival Rate Estimate The 10-year survival rate estimate (95% CI) for 766 pre-existing and new SSC restorations was 82.6% (78.8%, 85.9%) [Pages , Table 31 & Figure 19].

65 51 When pre-existing SSCs were excluded, the 10-year survival rate estimate (95% CI) for the 650 new SSC restorations was 79.2% (73.0%, 84.2%) [Pages , Table 32 & Figure 20]. The 10-year survival rate estimate (95% CI) for 116 pre-existing SSC restorations was 87.0% (85.4%, 88.4%) [Pages , Table 33 & Figure 21]. The median follow-up for SSC restorations was 5.1 years, with an interquartile range (IQR) of , and min-max values of years [Pages , Table 34, Figures 22 & 23]. The 10-year survival rate estimate (95% CI) for 1651 pre-existing and new AM restorations was 76.9% (72.0%, 81.1%) [Pages , Table 35 & Figure 24]. When pre-existing AMs were excluded, the 10-year survival rate estimate (95% CI) for the 1011 new AM restorations was 63.5% (55.7%, 70.4%) [Pages , Table 36 & Figure 25]. The 10-year survival rate estimate (95% CI) for 640 pre-existing AM restorations was 63.6% (50.1%, 74.3%) [Pages , Table 37 & Figure 26]. The median follow-up for AM restorations was 6.9 years with IQR of , and min-max values of years [Pages , Table 34, Figures 22 & 23]. As only 3 CR restorations were placed at MSH Dentistry Clinic, only the 201 pre-existing CR restorations could be analyzed. The 10-year survival rate estimate (95% CI) for the 201 preexisting CRs was 37.0% (14.3%, 60.2%) [Pages , Table 38 & Figure 27]. The median follow-up for CR restorations was 2.3 years with IQR of , and min-max values of years [Pages , Table 34, Figures 22 & 23].

66 52 Figure 28 on page 134 compared the survival rate estimates between all SSC and AM restorations. Figure 29 below demonstrated the survival curve for new SSC and AM restorations. In both, the survival curve dropped off more quickly for the AM restorations, which indicated a greater hazard for AM as compared to the SSC restorations. Figure 29 showing the survival curve comparison between new amalgam and SSC restorations Figure 30 below compared the survival rate estimates between pre-existing SSC, AM and CR restorations. The survival curve for the CR restorations considerably fell within the first 5 years, as compared to the relative success of both AM and SSC restorations.

67 53 Figure 30 showing the survival curve comparison between pre-existing amalgam, composite resin and SSC restorations Survival rate estimates were conducted for new SSC and AM restorations by age at placement (Pages , Tables 39 & 40 and Figures 31 & 32), gender (Pages , Tables 41 & 42 and Figures 33 & 34) and location (Pages , Tables 43 & 44 and Figures 35 & 36). None of these variables revealed a clinically meaningful difference to the survival of the respective restoration types. Across all analyses, combined, new and pre-existing, SSC restorations had a greater survival rate estimate as compared to AM and CR.

68 54 (g) Crude Success Rates for New SSC and Amalgam Restorations The crude success rate during patient follow-up was 89.2% for the 650 new SSC restorations and 61.5% for the 1011 new AM restorations [Page 147, Table 45 & Figure 37].

69 55 2. Part 2: Radiographic Assessment of SSC Restorations Sixty-one patients had at least one post-ssc radiograph, representing 245 radiographs captured (127 bitewing films; 118 periapical films). See Images 1-4 for examples of digitized bitewing and periapical films used for analyses. Images 1 and 2: Radiographic examples of bitewing films from two different patients used to measure alveolar bone loss from mesial and distal sites of the respective SSC restored teeth. Sites were recorded for tooth 46 from Image 1, and tooth 37 from Image 2. Red arrows in Image 1 are identifying the CEJ. Images 3 and 4: Radiographic example of periapical films from the same patient taken prior to and following SSC restorations used to record PAI scores. PAI scores were recorded for teeth 46 and 47 from this example.

70 56 (a) Alveolar Bone Loss Measurements From the 127 bitewing (BW) radiographs, the mean alveolar bone loss recorded from mesial and distal sites of SSC restored teeth was 1.36mm ( ) and 1.40mm ( ) respectively. One hundred twenty-six (99.2%) of distal sites and 100.0% of mesial sites measured 3mm or less, with the majority for both recorded within the mm range. From the alveolar bone loss measurements recorded from the distal site, 117 were regarded as normal (non-resorbed) and 10 as resorbed (>2mm). From the alveolar bone loss measurements recorded from the mesial site, 119 were regarded as normal (non-resorbed) and 8 as resorbed (>2mm) (See Table 46 Below). Site of Measurement Alveolar Bone Loss Measurement (mm) Mesial Site of SSC Distal Site of SSC Number Total (/254) Percentage Total Table 46 showing the frequency of alveolar bone loss measurements surrounding SSC restored teeth from mesial and distal sites

71 57 (b) Periapical Index (PAI) Scores and Pulpal Status of SSC restored teeth From the 59 Pre-SSC periapical (PA) radiographs, fifty had a PAI score of 1 with normal periapical structure, and nine had a PAI score of 2, indicative of small changes in periodontal bone structure. From the 59 Post- SSC PA radiographs, forty-nine had a PAI score of 1 with normal periapical structure, and ten had a PAI score of 2, indicative of small changes in the periodontal bone structure. PAI score changes were recorded for 13 SSC restorations; seven worsened slightly from 1 to 2 and six improved from 2 to 1. The PAI scores for the remaining 46 SSC restorations remained unchanged. The mean (SE) of 59 PA radiograph pre-post intervals was 8.4 years (0.39), with a range of years [Page 148, Table 47].

72 58 F. DISCUSSION 1. Stainless Steel Crown Restorations Minimal published data exists demonstrating the clinical and radiographic outcomes of stainless steel crown (SSC) restorations on the permanent posterior dentition. This retrospective cohort study was the first investigation to assess the long-term clinical and radiographic outcomes of the SSC as a posterior permanent tooth restoration. This study has fulfilled the proposed aims and objectives as follows: 1) The SSC restoration of the permanent posterior dentition demonstrated a high clinical 10-year survival rate estimate of 82.6% (combined), 79.2% (new) and 87.0% (pre-existing), with a median follow-up period of 5.1 years ( years). 2) There were 883 failed restorations from the 2621 combined pre-existing and new restorations reported, including 120 (58.8%) CRs, 672 (40.7%) AMs, and 91 (11.9%) SSCs. 3) The most common reported failure of the SSC led to extraction (61.5%), followed by replacement of SSC (36.3%), and SSC recementation (2.2%). The most common diagnoses for extraction was secondary to periodontal disease (44.6%), followed by pulpal pathology/necrosis (37.5%), and caries (14.3%). 4) The SSC restoration of the permanent posterior dentition demonstrated a superior survival rate estimate as compared to amalgam restorations (10-year survival rate estimate of 76.9% (combined AM), 63.5% (new AM), and 63.6% (pre-existing AM).

73 59 5) The pre-existing SSC restoration of the permanent posterior dentition demonstrated a superior 10-year survival rate estimate (87.0%) as compared to the pre-existing amalgam (63.6%) and composite resin restorations (37.0%). 6) Replacement of restoration was the most commonly reported result of AM and CR restoration failures; 434/672 (64.6%) and 94/120 (78.3%) respectively. The remaining 35.4% of AM and 21.7% of CR failures resulted in extractions. 7) There were 259 (59.6%) and 57 (60.6%) failed AM and CR restorations respectively that were replaced with SSCs. 8) From the 127 BW radiographs, the mean alveolar bone loss recorded from mesial and distal sites of SSC restored teeth was 1.36mm ( ) and 1.40mm ( ) respectively. Mesial and distal alveolar bone loss was recorded as 3mm or less in 99.6% of cases. 9) From the 118 PA radiographs evaluated prior and following the placement of SSC restorations over a mean interval of 8.4 years ( ); the recorded PAI scores documented were 1 or 2, indicative of periodontal structures that were within normal limits. The results of this study revealed that SSCs are effective, durable and should be recommended as a treatment option for full coronal restoration of the posterior permanent dentition. Despite not being a lab-fabricated restoration, the SSC had a negligible effect on the surrounding periodontium, while maintaining the vitality of the respective tooth. Compared to conventional multisurface intra coronal restorations, whether pre-existing or placed at the MSH Clinic, the SSC restoration demonstrated the greatest success, survival and performance.

74 60 (a) Stainless Steel Crown Reported Failures The 271 subjects in the study comprised 766 SSCs that included 116 pre-existing and 650 newly placed restorations at the MSH Dentistry Clinic. There were 91 (11.9%) reported failures of the SSC restoration, which resulted in extraction (61.5%) and replacement of the SSC (36.3%). The most common diagnoses for extractions were secondary to periodontal disease (25/56), followed by pulpal pathology/necrosis (21/56). Periodontal disease was documented when treatment was conducted without the notation of caries, tooth or restoration fracture, pulpal pathology or necrosis. This may be considered as a censored failure of the SSC restoration as the tooth was extracted due to the mobility of the tooth, unrelated to the SSC restoration but deemed as a failure secondary to extraction. There were 25 SSC restored teeth extracted due to chronic periodontal disease. Fourteen of these extractions were from four patients. Similarly, seven patients accounted for 29 of the 37 AM restored tooth extractions due to periodontal disease. For both SSC and AM, fifteen patients accounted for each of the respective total extractions, to which five patients (33.3%) had both SSC and AM restored teeth extracted. This demonstrated a cluster failure effect that further supported the diagnosis of chronic periodontal disease unrelated to the type of restoration placed. It is difficult to know whether the SSC restored teeth that were assessed as failures and extracted due to pulpal pathology and necrosis (21/56) had pre-existing pulpal pathology without radiographic periapical involvement. Eighty six percent (559/650) of SSCs placed were due to the presence of caries and of these, 271 were placed secondary to failed conventional restorations. Furthermore, the patient demographic did not allow for reliable vitality testing to be conducted, or accurate patient feedback regarding symptoms commonly associated with pulpitis.

75 61 However, with clinical and radiographic results combined, only 2.7% (21/766) of all SSCs demonstrated pulpal pathology/necrosis, thus supporting SSCs maintenance of tooth vitality. Recementation was considered a failure as it was assumed that the initial placement was inadequate in its adaptation/cementation and required subsequent removal, re-adaptation and cementation. This was a reported failure for two SSC restorations (2.2%) in the present study. Interestingly, occlusal perforation of the SSC was recorded in only 29 instances (3.8%), in a population of whom 79.0% had documented grinding habits. From the recorded occlusal perforations, 12 were regarded as failures as they were replaced with new SSC restorations. The remaining 17 occlusal perforations were repaired with AM and were not regarded as failures, as the SSC remained intact with sealed margins, and in the absence of recurrent decay or pathology. These amalgam restorations were not considered in the overall amalgam analyses, as they were not deemed as conventional restorations. These designations were in agreement with previous publications that defined survival as the crown remaining in situ with or without modification during the entire observation period (De Backer et al., 2007; Pjetursson et al., 2007; Van Nieuwenhuysen et al., 2003). In contrast, Roberts & Sherriff (1990), considered the occlusal perforation of a permanent SSC to be a failure of the restoration. As such, in their evaluation of 43 permanent molar SSCs over a 10-year period, a single failure was reported due to the occlusal perforation of a SSC (Roberts and Sherriff, 1990). Despite differences in definitions of failure, Roberts & Sherriff (1990) had a comparable prevalence of SSC occlusal perforation to that reported in the present study, 2.3% and 3.8% respectively. Unfortunately due to their small sample size of 43 permanent SSC restorations, they were unable to conduct a survival analysis.

76 62 (b) Stainless Steel Crown Survival Analysis The present study was the first to demonstrate a survival analysis for the SSC restoration as a viable restoration for permanent posterior teeth. The survival rate estimate could be predicted accurately up to 14 years using both combined and new SSC restorations, and up to 18 years based on data obtained from pre-existing SSC restorations. The 10-year survival rate estimate (95% CI) for 766 pre-existing and new SSC restorations was 82.6% (78.8%, 85.9%) with a median follow-up of 5.1 years and range of years. When pre-existing SSCs were excluded, the 10-year survival rate estimate (95% CI) for the 650 new SSC restorations was 79.2% (73.0%, 84.2%). Ten-year survival rate estimates for SSC restorations of the primary dentition did not exist. In order to compare the permanent SSC survival to that commonly reported for the primary dentition, the survival estimates for two, five and eight years were assessed. As such, the newly placed permanent SSC had predicted survival rate estimates of 97.2%, 92.7%, and 87.5% at 2, 5 and 8 years respectively. The combined and pre-existing permanent SSC had similar results. The survival rate estimates provided for the permanent SSC restoration was either comparable or outperformed that reported for SSCs placed in the primary dentition. Einwag & Dunninger (1996) stated the survival rate of SSCs placed in the primary dentition was 90.0% after 4.5 years, and 83.0% after 8 years (Einwag and Dunninger, 1996). Roberts and Sherriff (1990), documented a similar 5-year survival rate of 92.2%(Roberts and Sherriff, 1990). In addition, Al- Eheideb & Herman documented a survival rate of 95.5% for SSC over a period of 27 months (Al-Eheideb and Herman, 2003).

77 63 In order to compare the SSC restoration to treatments that would be performed more commonly on the posterior permanent dentition, literature was compared which included the use of cast full metal lab fabricated crowns. Van Nieuwenhuysen et al. (2003) conducted a long-term evaluation of permanent dentition restorations, which included 722 amalgams, 115 composite resins and 89 FMCs. The reported 75% survival time for the FMC restoration was 11 years, notably superior to that for the conventional restorations, reported as 2 and 6.5 years for CR and AM, respectively (Van Nieuwenhuysen et al., 2003). The SSC restoration as documented in the present study appeared to perform superior to that of the FMC. As for the new SSC restorations, the 75% survival time equated to 12 years, and between years for pre-existing SSC restorations. The 75% survival time for the combined pre-existing and new SSC data could not be accurately predicted from the respective survival curves, as it would coincide with a time point greater than 14 years. Pjetursson et al., (2007) conducted a meta-analysis assessing the 5-year survival rates of allceramic single crowns as compared to the survival rates of PFM crowns. Similar to the definitions used in this present study, survival was defined as the crown remaining in situ with or without modification during the entire observation period. For all-ceramic crowns and for PFM, 430/6006 and 160/1765 crowns were reported as lost, translating to a 5-year survival of 93.3% and 95.6% respectively. These results were comparable to the study of SSC restorations, with the 5-year survival of 93.8% (combined SSC), 92.7% (new SSC), and 94.9% (pre-existing SSC). Lastly, De Backer et al. in 2006 investigated 456 patients, comprised of 1036 full crowns (cast gold or PFM) that were evaluated over a sample period of 18-years. Similar to the present study

78 64 (86.0%), the most common reason for full crown preparation was the extensive loss of crown structure due to caries (65.9%). The reported survival rates after 12 years for the FMC/PFM restorations was 86.4% (molars) and 86.6% (premolars). This was one of the few studies reported which demonstrated greater survival estimates than the SSC restoration. The 12-year survival rate estimate for the SSC restoration was between %, dependent on whether assessed from the combined, new, or pre-existing SSC survival curves. Potential reasons for the discrepancy could be from the different population demographics, as the aforementioned study was comprised of healthy adults with good oral hygiene, attending a graduate prosthodontics specialty clinic, and many of which received multiple full coverage restorations. In addition, De Backer et al., classified failures as irreversible (true) if the full crown or tooth was lost, however considered recementation a reversible complication and was not regarded as a failure. It is unclear through the documentation of the report as to what percentage was classified as having reversible complications, although stated within the results was that 69.0% had loss of retention (De Backer et al., 2006). This could potentially change the survival analysis that was conducted, had recementation been considered as a true failure. 2. Conventional Restorative Treatments (a) Conventional Restoration Reported Failures For the survival assessment of conventional restorative treatments of the posterior permanent dentition in this study, a failure was considered to have occurred if endodontic therapy, replacement, placement of a different restoration, or extraction was conducted. Replacement of the restoration, utilizing the same material and extent (i.e. replacing a mesio-occlusal amalgam with a mesio-occlusal amalgam), was considered a failure of the restoration. The main reason

79 65 reported for replacement was the presence of caries. It can be postulated that the initial restoration may not have been placed in an ideal manner predisposing it to subsequent failure. Replacement of the restoration, utilizing the same material but requiring more restorative material for a larger restoration (i.e. removing a mesio-occlusal amalgam to place a mesioocclusal-distal amalgam) was also considered a failure for the purposes of statistical analyses and calculation of accurate survival estimates. However, these 126 amalgam failures may potentially be considered as censored data, as the previous restoration may have only been removed to permit the inclusion of new areas of decay adjacent to the existing restoration. As such, one cannot say that these were in fact true failures of the restoration. Conversely, had the study not classified this treatment as a true failure, the survival analyses for the 126 amalgams could have been embellished, as the replacement of the restoration would not have been counted as a failure. The definitions used in this study were consistent with those reported in other longevity studies of conventional restorations and allowed for comparison of results (Opdam et al., 2010; Opdam et al., 2007; Simecek et al., 2009; Van Nieuwenhuysen et al., 2003). (b) Survival Analysis of Conventional Restorations From the present study, the 10-year survival rate estimate (95% CI) for 1651 combined preexisting and new AM restorations was 76.9% (72.0%, 81.1%) with a median follow-up of 6.9 years ( years). When pre-existing AMs were excluded, the 10-year survival rate estimate (95% CI) for the 1011 new AM restorations was 63.5% (55.7%, 70.4%). The survival rate estimate could be predicted up to 30 years from the combined, new and pre-existing AM restorations.

80 66 The 30-year survival rate estimates (95% CI) for the AM restorations was 27.1% (8.0%, 51.0%) for new, 37.1% (11.4%, 63.5%) for pre-existing, and 53.5% (35.9%, 68.3%) for the combined. As only 3 CR restorations were placed at MSH Dentistry Clinic, only the 201 pre-existing CR restorations could be analyzed. From the 201 pre-existing CR restorations, the 10-year survival rate estimate (95% CI) was 37.0% (14.3%, 60.2%) with a median follow-up of 2.3 years ( years). The survival rate estimate could be accurately predicted up to 30 years (95% CI); 15.5% (5.3%, 30.7%). These results were similar to those reported by Opdam et al. (2010), in which the 12 year survival estimate was stratified by the patient s caries risk. For the patients documented as having high caries risk, the twelve-year survival estimate for AM restorations was 62.8%, whereas for CR restorations was 66.8% (Opdam et al., 2010). Especially in the high caries risk group, caries was more frequently reported as the reason for failure for CR as compared to AM restorations. This trend was consistent in the present study and with other studies demonstrating increased rates of secondary caries adjacent to CR restorations in high caries risk populations (Simecek et al., 2009; Soncini et al., 2007; Van Nieuwenhuysen et al., 2003). Opdam et al. postulated the reason for greater success of the CR restoration within their study, was that fewer surfaces were involved, as compared to the larger AM restorations. Aside from the studies by Opdam et al., the majority of reported literature coincides closer with the findings from Simecek et al. (2009), Soncini et al. (2007) and the present study. All demonstrated greater success and longevity of the AM restoration over the CR restoration for the posterior permanent dentition. In addition, a consensus existed amongst survival studies of the primary posterior dentition, which demonstrated the superior success and longevity of the SSC as compared to that of

81 67 conventional restorations (Braff, 1975; Dawson et al., 1981; Eriksson et al., 1988; Messer and Levering, 1988; Roberts and Sherriff, 1990; Seale and Randall, 2015). Roberts & Sherriff (1990) assessed the 5-year survival rate of SSC and Class II AM restorations placed in the primary posterior dentition. The reported 5-year survival rates of the primary SSC restoration was 92.2%, Class II AM was 80.7%. In light of the paucity of literature concerning the comparison of SSC and conventional restorations of the posterior permanent dentition, the results from the aforementioned studies were evaluated together. Combined, they supported the results found in the present study, which demonstrated the greater performance and survival of the SSC as compared to conventional restorations at each respective time point of analyses. In the survival curve comparing new SSC and AM restorations, there is an apparent greater hazard for AM as the curve descended more rapidly. This relationship was again repeated in the survival curves of the pre-existing restorations where the CR had the greatest hazard, followed by AM and then SSC restorations. (c) Replacement of Conventional Restorations with SSCs In the present study, extraction represented the majority of SSC failures (61.5%), whereas this was reported in only 35.4% and 21.7% of AM and CR failures respectively. For the conventional restorations, it was more common for replacements to be performed rather than extractions. Interestingly, the SSC restoration was primarily used to replace both AM (59.6%) and CR (60.6%) failed restorations. As such, the SSC could be viewed as the restoration of last resort; when the caries were extensive, or conventional restorations had failed, it was the SSC that could still reliably be placed. It should also be noted that had the SSC not been available, there could

82 68 have been a greater number of extractions following the failure of conventional restorations. 3. Radiographic Evaluation The present study was the first to investigate the pulpal status of SSC restored permanent teeth and the potential effect on the surrounding periodontium. (a) Pulpal Status of SSC Restored Teeth The pulpal status was evaluated from 118 periapical radiographs with a median duration of 8.4 years ( years), taken prior and following the placement of a SSC restoration. The widely utilized Periapical Index (PAI) scoring system developed by Orstavik (1986) was used to determine the absence, presence, or transformation of disease state. From the 59 Pre-SSC periapical (PA) radiographs, fifty had a PAI score of 1 with normal periapical structure, and nine had a PAI score of 2, indicative of small changes in periodontal bone structure. As reported throughout the endodontic literature, a PAI score of 1-2 was commonly regarded as healthy, healed or minimally inflamed, whereas a score of 3-5 was diseased (Kerosuo and Orstavik, 1997; Orstavik et al., 1986; Ridao-Sacie et al., 2007; Trope et al., 1999). The results from this study revealed 100.0% of the teeth evaluated, both prior and following the placement of SSC, to be healthy, healed, or minimally inflamed. Interestingly, for 13 SSC restorations, there was a near split between the respective PAI scores changing in both positive and negative directions. Seven worsened slightly from 1 to 2, and six improved from 2 to 1. Although all maintained a healthy overall score. It may be speculated that for the six that improved, the full coverage crown may have provided an optimal protected

83 69 environment that could foster pulpal repair, minimize inflammation and preserve the vitality of the tooth. As for the seven that worsened, it may be postulated that these teeth may have had signs of pulpal inflammation not visible on a radiograph prior to the placement of the SSC restoration. (b) Alveolar Bone Measurements of SSC Restored Teeth The measurement of alveolar bone loss on BW radiographs recorded from the alveolar crest to cementoenamel junction was a consistently utilized outcome measure across the literature in both primary and permanent dentitions. It was further agreed upon that a distance of 2mm or less was to be considered healthy/non-resorbed, whereas a distance greater than 2mm was to be considered as resorbed/diseased (Bimstein et al., 1988; Bimstein and Garcia-Godoy, 1994; Bimstein et al., 1993; Bimstein et al., 1996; Knoernschild and Campbell, 2000; Sharaf and Farsi, 2004). In the present study, ninety-three percent of the 254 mesial and distal sites recorded from the 127 SSC restored teeth were classified as healthy/non-resorbed. Sixteen sites measured between mm, and a single site was greater than 3.01mm. The findings from this study coincided with previously published work that evaluated alveolar bone loss surrounding SSC restored primary molars (Bimstein, 1992; Bimstein et al., 1988; Bimstein and Garcia-Godoy, 1994; Bimstein et al., 1996; Sharaf and Farsi, 2004). These studies examined various parameters and confirmed that crown marginal extension or adaptation, preservation of tight proximal contacts, or duration of crown existence did not significantly affect interproximal bone resorption.

84 70 (c) Limitations of Radiographic Evaluation For the present study, it should be noted that due to poor cooperation, all active patients at the MSH Clinic did not have diagnostic radiographs available for analysis. Further, some patients whom required diagnoses and treatment under general anesthetic had a limited number of radiographs, as the frequency of radiographs was dependent on the frequency of GA procedures. Besides alveolar bone loss and PAI scores, there was no evaluation of the quality of the SSC restoration in terms of adequacy or inadequacy. Conversely, Sharaf and Farsi (2004), recorded the quality of the SSC as either adequate when all margins were smooth and well adapted covering all dentin, or inadequate, when crown margins appeared too short, extended below the CEJ, or away from the tooth surface by more than 1 mm (Sharaf and Farsi, 2004). However, the present study was the first to examine alveolar bone loss surrounding SSC restorations, and despite not being lab-fabricated demonstrated negligible effects on the surrounding periodontium. 4. Data Analysis (a) Agreement Analysis Agreement analysis for transcription accuracy was conducted during the pilot trials to ensure standardization of the primary investigator. Inter and intra- rater reliability utilizing Cohen s Kappa test was not appropriate for this data set, as there were minimal categorical variables that had subjective basis(landis and Koch, 1977).

85 71 (b) Inferential Statistics Inferential statistics could be applicable to the comparison of the longevities between restoration types, and/or the comparison of longevities for various subgroups. However, no inferential analyses were conducted, as the data was hierarchical in nature: restorations within teeth, and teeth within a patient. Further, subjects could contribute observations of more than one type of restoration, tooth location, and more than one age at placement. (c) Cox Proportional Hazards Model and Logrank Tests Due to the aforementioned hierarchical nature of data, there were no pre-programmed procedures in SAS that could fit a Cox Proportional Hazards (PH) model. Prior to fitting such a model, it was important to ascertain whether the assumptions underlying the model were met. This could be done in SAS. The following checks were programmed in SAS: 1. Proportional hazards assumption: a. Log Cumulative Hazard Plots: For each covariate, the log of the cumulative hazard was plotted against longevity. If the proportional hazards assumption holds, these curves should be parallel to one another and the distance between them should remain constant over time. b. Cumulative Hazard Plots: For each covariate, one level serves as a reference. The cumulative hazard plot for each of the other levels of this covariate is plotted against the cumulative hazard function for the reference level. If the proportional hazards assumption holds, these plots should resemble straight lines.

86 72 c. Plot of Differences in Log Cumulative Hazards: For each covariate, one level serves as a reference. The difference between the log cumulative hazard for this level and each other level is calculated. These differences are plotted against longevity. If the proportional hazards assumption holds, then the plots should remain constant over time. 2. Presence of outliers: a. Deviance Residual Plots: The deviance residuals are plotted against the risk score (β! x). Outliers are detected in the usual manner. 3. Presence of influential observations: a. For each covariate, the DFBetas are plotted against observation number. Influential observations are those lying away from the main body of observations 4. Overall Model Fit: a. The cumulative hazard function of the Cox-Snell residuals is plotted against the Cox- Snell residuals. If the model fits well, this plot should appear as a straight line through the origin. It would have been desirable to conduct a statistical test for the equality of longevities for the different restoration types. A logrank test however was not possible because the groups (restoration types) were not independent of one another. Each subject/tooth combination could contribute observations to any, or all of the different restoration types. A test for differences could be carried out within the context of a regression model, if a suitable model could be found. There was an R package that fits Cox PH models to data with up to 2 levels of hierarchy with random effects (frailties). However, as mentioned above, prior to fitting the model, the necessary assumptions must be checked.

87 73 Three cases were considered within the present studies analysis: (i) new restorations only, (ii) pre-existing restorations only, and (iii) new and pre-existing restorations combined. The plots used to make a visual assessment of the proportional hazards assumption revealed serious departures from proportionality in all three cases. The hazards for amalgam and composite resin restorations could potentially be assumed to be proportional in cases (ii) and (iii). However, the hazards for amalgam and SSC restorations (and composite resin vs. SSC restorations) could not be considered to be proportional. In each of the three cases, there were a large number of influential observations. Had there been just a few, it would be reasonable to remove them to see what effect, if any, they might have on the PH assumption. However, it did not seem reasonable to remove a larger quantity of observations unless there was a good clinical reason. For these reasons, the Cox PH modelling to test for differences in restoration type longevities did not proceed any further. (d) Multivariate Cox Proportional Hazards (PH) Regression for Each Restoration Type For new restorations, the possibility of fitting a Cox PH model separately to the amalgam and SSC longevities was investigated in order to examine the joint effect of age, gender, location (upper vs. lower and right vs. left) on longevity. Based on the product-limit estimate plots, one could appreciate the survival curves for female and male genders were nearly identical, for both amalgam and SSC restorations. One would therefore expect that the proportional hazards assumption would hold for gender. The same could be said for the remaining covariates (age, location (upper vs. lower and right vs. left).

88 74 For amalgam restorations, one could make a case for proceeding to a Cox PH regression as all of the assumption checks were either met, or nearly met. For SSC restorations, the assumption checks were not as straightforward to interpret. Some of the plots indicated there could be departures from the assumptions, and the overall fit may not be as good as it could be. However, it s possible that the plots were affected by the relatively small number of SSC failures. There were also a fairly large number of the observations that were outliers and/or were overly influential. Had there been just a few, it would be reasonable to remove them to see what effect, if any, they might have had on the assumptions. However, it did not seem reasonable to remove a larger quantity of observations unless there was a good clinical reason. Therefore, it did not seem reasonable to proceed with Cox PH regression for the SSC restorations. As multivariate regression was not one of the main objectives, the present data analysis did not pursue fitting a model with these covariates, for either amalgam or SSC restorations. While there are some statistical methodologies available for modeling multi-level hierarchy for censored data, there was little software available for fitting such models. Further research would be required to identify statistical methods and software appropriate for the structure of the data in the current study. 5. Demographics and Implication for Practice The study population included active, registered patients from Mount Sinai Hospital s Dentistry Clinic, which encompassed those with clearly identified disabilities or special needs. Eightyeight percent were reported as having four or more co-morbid conditions, and the potential functional limitations for these patients included cognitive, receptive, expressive language,

89 75 learning, and/or motor ability deficits (Accardo et al., 2002; Merry and Edwards, 2002; World Health Organization., 2001). Mental retardation was a captured co-morbid condition within the comprehensive chart review, however is a term that has been eliminated from medical diagnoses. According to the American Psychiatric Association s fifth revision of its Diagnostic and Statistical Manual for Mental Disorders (DSM-5), the term mental retardation has been replaced with intellectual disability (American Psychiatric Association, 2013). Sixty five percent of the patients were reported as being high caries risk with nearly 90.0% having fair-poor oral hygiene. This agreed with other studies stating the known high prevalence of caries and oral disease in adults with special needs (Chohayeb, 1985; S. Hulland and Sigal, 2000; Sigal and Sigal, 2006; Tesini, 1981). Sixty percent of the patients were taking a prescribed medication, specifically a psychotropic agent, which are known to cause xerostomia and further contributed to their high caries risk status (Sreebny and Schwartz, 1997). Assessing the success of restorative treatments in a population that was at the greatest risk for restoration failure provided additional credibility to the results. Although generalizability of results cannot be claimed due to the unique nature of the study population, it can be postulated that the success of the restorations would only improve in those with a lower caries risk status. For healthy individuals requiring the use of general anesthetic for dental care, geriatric populations, or persons with limited finances and/or dental coverage, one would expect the SSC restoration of a posterior permanent tooth to be an effective long-term treatment option. As such, there should be increased advocacy for the use and application of the SSC restoration. Beginning within educational settings with core didactic and clinical curriculum to practicing clinicians, governmental legislature and public health settings. The results from the present study support the SSC to be recommended as the restoration of choice for failed conventional restorations and

90 76 multisurface decay of the permanent posterior dentition. 6. Limitations and Strengths One of the limitations of the present study included the retrospective design relying on the accuracy of clinical records and radiographs available in patient charts. The Evidence-Based Medicine Levels of Evidence (Oxford Centre for Evidence Based Medicine, 2009) indicated that the highest level of evidence (level 1a) is represented by a systematic review of randomized controlled trials (RCTs). These rank the highest due to the fact that they are not susceptible to bias. The second highest level of evidence (level 1b) described was a RCT with narrow confidence intervals requiring a large sample size. Unfortunately, RCTs have disadvantages of non-compliance and high dropout rates (Needleman et al., 2005). Randomized controlled trials with dropout rates documented as greater than 20.0% are considered low quality RCTs. Systematic reviews restricted to high quality RCTs included small number of RCTs and the main conclusion commonly provided was that more high-quality RCTs are to be conducted. The present design allowed for a larger sample size, with greater lengths of follow up to be studied. In addition, multiple operators of varying years of practice performed all treatments conducted at the MSH Clinic. This included recent graduates enrolled as one-year hospital dental residents, rotating pediatric graduate students from the University of Toronto, and staff dentists. The treatments were also conducted across a variety of settings, including within the clinic using local anaesthesia and in the operating room with general anaesthetic. The potential advantage of multiple operators, and multiple environments would be that the outcome is more likely due to a superior technique rather than a superior single operator.

91 77 Another strength of this study was that the chart and radiographic analysis relied solely upon the principal investigator. In order to standardize the PI s chart entry and radiographic analysis, a standardization and agreement analysis was completed. Agreement analysis revealed a high level of agreement between raters with a score of 98.4% for the chart review and 100.0% for radiographic assessment. A single investigator was responsible for all data collection thereby minimizing the risk of variance versus using multiple research assistants. Other potential limitations of this study included that it was single-centered encompassing philosophies of practice that could introduce bias, specific to the treatments provided. The fact that patients did not always have routine follow up was an additional limitation. Ideally patients would have had routine clinical and radiographic follow up of their treated teeth. This is in part due to the unique patient demographic of the sample population and in part that some patients returned to their local community dentists for continued recall care. Another limitation of the present study was not having access to dental information prior to the patient s enrollment at the MSH Dentistry Clinic. As such, there were pre-existing restorations that were designated as censored data. A limitation of interpreting this data was the length-sampling bias, as pre-existing restorations had to survive long enough to be present at the initial visit at the MSH Clinic. As such, longevity for these restorations was at least as long as what was recorded during follow-up at the MSH Clinic. 7. Future Directions In the current retrospective cohort investigation, the SSC restoration was assessed from active registered patients at the MSH Dentistry Clinic. Further studies in the form of prospective, multicenter clinical trials with healthy patients of all ages should be evaluated. All restorations of the

92 78 permanent posterior dentitions should be recorded over at least 10 years, with complete documentation of diagnoses and treatment conducted. Periodontal parameters and biomarkers of inflammation, including neutrophils and matrix metalloproteinases, should be used to assess the gingival crevicular fluid surrounding dental restorations (SSC vs. conventional restorations) to further explore the periodontal health. Radiographs should be evaluated prior and following the placement of SSC restorations on the permanent posterior dentition. Specifically, radiographic analyses of the SSC restoration in the posterior permanent dentition should be conducted that evaluates the quality of the crown restoration. This should include the documentation of marginal adaptation, coronal structure coverage, crown length and whether located too short or long below the CEJ. These analyses can then be further compared to the survival and outcomes of the SSC restoration. Together, this could provide greater clinical and radiographic evidence to extend the generalizability in terms of recommendations for the use of SSCs as a long-term permanent posterior tooth full coronal coverage restoration.

93 79 G. CONCLUSIONS 1. The SSC restoration of the posterior permanent dentition demonstrated a high clinical 10-year survival rate estimate of 82.6% (combined), 79.2% (new) and 87.0% (pre-existing), with a median follow-up period of 5.1 years ( years). 2. Caries was the most common diagnosis for the placement of SSCs (86.0%) and amalgam restorations (98.0%). 3. The most common reported failure of the SSC led to extraction (61.5%), followed by replacement of SSC (36.3%), and SSC recementation (2.2%). 4. The most common diagnoses for extraction of SSC restored teeth was due to periodontal disease (44.6%), followed by pulpal pathology/necrosis (37.5%), and caries (14.3%). 5. Newly placed SSC restorations of the permanent posterior dentition demonstrated a superior 10-year survival rate estimate (79.2%) as compared to the newly placed amalgam restorations (63.5%). 6. The combined newly placed and pre-existing SSC restoration of the permanent posterior dentition demonstrated a 10-year survival rate estimate of 82.6%. This is superior when compared to combined newly placed and pre-existing amalgam restorations (76.9%). 7. The pre-existing SSC restoration of the permanent posterior dentition demonstrated a superior 10-year survival rate estimate (87.0%) as compared to the pre-existing amalgam (63.6%) and composite resin restorations (37.0%).

94 80 8. Replacement of restorations accounted for most amalgam and composite resin failures. The SSC restoration was primarily used to replace both AM (59.6%) and CR (60.6%) failed restorations. 9. With 99.6% of mesial and distal alveolar bone height measurements recorded as 3mm or less, the SSC restoration demonstrated negligible effects on the surrounding periodontium. 10. With one hundred percent of the teeth evaluated prior and following the placement of SSC restoration recorded with PAI scores of 1 or 2, the SSC restoration demonstrated negligible effects on tooth vitality. 11. The SSC restoration represents an effective long-term treatment option for the restoration of the permanent posterior dentition based on a large sample size and long follow-up period.

95 81 TABLES AND FIGURES Table 1. Study Population and Gender Distribution Gender N (%) Male 160 (59.0%) Female 111 (41.0%) All 271 Figure 1. Gender distribution of study population

96 82 Table 2. Study Population Age Distribution Summary Statistic Age at First MSH Clinic Visit Age at First New Restoration Age on March 31, 2015 N Mean (SE) 30.2 (0.85) 33.2 (0.91) 42.7 (0.92) Median Min - Max Figure 2. Age of study population as of March 31 st, 2015

97 83 Figure 3. Age of study population at first clinic visit (MSH Clinic) Figure 4. Age of study population at time of first restoration (MSH Clinic)

98 84 Table 3. Distribution of Medical Conditions Amongst Study Population Number of Patients Medical Condition with Condition Percentage (/271) ADD/ADHD/Autism (unspecified) ADD ADHD Autism Alzheimer s Disease/Dementia Cerebral Palsy Cerebral Vascular Accident (CVA/Stroke) Craniofacial Anomaly Cognitive impairment (ex. Memory/concentration) Developmental Delay Down s Syndrome Facial pain disorders Fainting spells Hearing disorder Malignant hyperthermia Mental Retardation (Unspecified=1) Mild Mental Retardation (2) Moderate Mental Retardation (3) Severe/profound Mental Retardation (4) Migraine or Recurring headaches Multiple Sclerosis Muscular Dystrophy Parkinson s disease Psychiatric disorder Seizures/Epilepsy Sight disorder (not correctable with glasses) Sleep problems Spina Bifida Traumatic/Acquired Head or Brain injury Has Shunt CNS Other Anemia Angina/chest pains Artificial/prosthetic heart value or artery/vein Bleeding or clotting disorder (Unspecified) Haemophilia (2) Sickle cell anemia (3) Thalassemia (4) 0 0.0

99 Other (5) Prolonged bleeding (ex. after cut or extraction) Blood clots in leg or other blood vessels (Deep vein thrombosis) Easy bruising Congenital heart disease (Unspecified) VSD ASD Tetrology of Fallot Mitral valve prolapse Eisenmenger s Complex Other Congenital heart disease Congestive heart failure Cyanosis Pacemaker History of a blood or blood product transfusion Heart attack Heart surgery High or low blood pressure (Unspecified) High blood pressure (specified) Low blood pressure (specified) Irregular pulse or heartbeat Limits to walking/work/exercise/sports Rheumatic fever Other CVS Condition Asthma Collapsed lung Smoker Cigarette smoker Cigar smoker Marijuana smoker Pipe smoker Other smoking product Emphysema Nasal or sinus problems Pneumonia Pulmonary embolus/blood clot Shortness of breath Sleep apnea Tuberculosis (TB) Other Respiratory Condition Cannot take aspirin

100 Dysphagia/Swallowing problem G or J Tube GERD Hepatitis/jaundice Hiatus hernia Intestinal or bowel disorders Irritable bowel syndrome Liver disease Recurring mouth ulcers Stomach/intestinal ulcers Upset stomach or diarrhea when taking medications Other GI Condition Allergies (unspecified) Allergy to Medications Environmental Allergies Dietary Allergies Antibiotic Allergies Local anesthetic allergies Other allergies Cancer Chromosome/Genetics Disorder Crohn s disease HIV/AIDs Metabolic disorders Rheumatoid /Osteoarthritis/ Arthritis Other Immune Condition Bladder problems Dialysis (Unspecified) Hemodialysis (specified) Peritoneal dialysis (specified) Prostate problems Renal problems Urinary tract problems Other GU Condition Diabetes (Unspecified) Type 1 Diabetes (insulin dependent) (2) 0 Type 2 Diabetes - Hypoglycemic medications (3) Type 2 Diabetes - Diet controlled (4) Hormone problems Pituitary problems Thyroid Problems (Unspecified) Hypothyroid (2)

101 Hyperthyroid (3) Other Endocrine Condition Taking medications to increase bone density 8 3 Artificial/prosthetic joint Jaw joint problems 8 3 Osteoporosis Physical impairment/disability/ WC bound Quadriplegia/Paraplegia or Paresis (unspecified) Quadriplegia/paresis (specified) Paraplegia/paresis (specified) Scoliosis Other MSK Condition Skin lesions/disorders Allergy/Hives/Rashes (unspecified) Hives (specified) Rashes (specified) Other Dermatology Condition

102 88 Table 4. Most Common Medical Conditions Amongst Study Population Medical Condition Number of Patients Identified Percentage (/271) Cognitive impairment Developmental delay Mental Retardation (MR) (Unspecified) Mild MR Moderate MR Severe MR Seizures/Epilepsy Physical impairment/disability/wheelchair bound Attention Deficit Disorder/ Attention Deficit Hyperactivity Disorder/ Autism (Unspecified) Autism (Specified) Quadriplegia/paresis Chromosome/Genetics Disorder Cerebral Palsy Asthma Dysphagia Scoliosis Hypertension GERD Hypothyroidism Paraplegia/paresis Congenital heart disease (Unspecified) Table 5. Number of Patients with Multiple Co-Morbidities Medical Conditions One Two Three Four Five Six Seven Eight Nine Ten >Ten Number of Patients Percent age (/271)

103 89 Table 6. Distribution of Medications Prescribed Amongst Study Population Medication Number of patients Percentage (/271) Any Medications Analgesics ASA Acetaminophen NSAIDS Narcotics/opioids Other Analgesics Antacids /H2 blockers Antibiotics (Daily, acute infection or prophylactically) Anticoagulants Antihypertensives Bisphosphonates Intravenous bisphosphonates (2) Oral bisphosphonates (3) Blood Transfusions Cortisone/Steroids Diuretics Generic cardiac medications Hormone Replacement Therapy Inhalers (Ventolin, etc.) Laxatives Muscle Relaxants Psychotropic Medications Seizure Medications Thyroid Medications Other medications Type 1 Diabetes (insulin dependent) (2) Type 2 Diabetes - Hypoglycemic medications (3) Taking medications to increase bone density 8 3.0

104 90 Table 7. Most Commonly Prescribed Medications Amongst Study Population Medication Number of Patients Percentage (/271) Psychotropic medications Anticonvulsant medications Inhalers Table 8. Insurance Coverage Distribution Type of Insurance Number of Patients Percentage (/271) No Insurance Ontario Disability Support Program (ODSP) Private Insurance 5 1.0

105 91 Table 9. Caries Risk, Oral Hygiene and Recall Frequency Recorded at Initial New Patient Exam (MSH Dentistry Clinic) Caries Risk, Oral Hygiene & Recall Frequency Distribution Severity Caries Risk Low Moderate High Number of Patients Percentage (/271) Oral Hygiene Number of Patients Percentage (/271) Recall Frequency Number of Patients Percentage (/271) Poor Fair Good Excellent Every three months (q3m) Every six months (q6m)

106 92 Table 10. Frankl Scale of Patient Behaviour/Cooperation Recorded at Initial New Patient Exam (MSH Dentistry Clinic) Frankl Scale Number of Patients Percentage (/271) Definitely Negative (- -) Negative (-) Positive (+) Definitely Positive (+ +)

107 93 Table 11. Number of Subjects, Teeth, and Restorations Category All subjects SSCs only AMs only CRs only Subjects (N) Teeth Total (N) Per subject Mean (SE) 7.5 (0.23) 2.7 (0.15) 6.0 (0.24) 3.4 (0.29) Median Min - Max Restorations Total (N) Per subject Mean (SE) 9.7 (0.37) 2.8 (0.16) 7.0 (0.33) 3.4 (0.30) Median Min - Max Per tooth Mean (SE) 1.3 (0.01) 1.0 (0.01) 1.2 (0.01) 1.0 (0.01) Median Min - Max

108 94 Figure 5. Number of teeth restored per subject by type of restoration Figure 6. Number of restorations per subject by restoration type

109 Figure 7. Number of restorations per tooth with majority of teeth receiving a single restoration 95

110 Figure 8. Number of restorations recorded by type with amalgam representing the greatest number, followed by SSCs and composite resin 96

111 97 Table 13. Number of Male Subjects, Teeth, and Restorations Category All subjects SSCs only AMs only CRs only Subjects (N) Teeth Total (N) Per subject Mean (SE) 7.7 (0.31) 2.7 (0.21) 6.3 (0.31) 3.3 (0.35) Median Min - Max Restorations Total (N) Per subject Mean (SE) 10.1 (0.48) 2.8 (0.22) 7.3 (0.41) 3.3 (0.35) Median Min - Max Per tooth Mean (SE) 1.3 (0.02) 1.0 (0.01) 1.1 (0.01) 1.0 (0.00) Median Min - Max Table 13 showing the number of male subjects, teeth, and restorations recorded within the study population

112 98 Table 14. Number of Female Subjects, Teeth, and Restorations Category All subjects SSCs only AMs only CRs only Subjects (N) Teeth Total (N) Per subject Mean (SE) 7.1 (0.35) 2.7 (0.23) 5.5 (0.38) 3.5 (0.49) Median Min - Max Restorations Total (N) Per subject Mean (SE) 9.1 (0.58) 2.8 (0.24) 6.5 (0.54) 3.6 (0.55) Median Min - Max Per tooth Mean (SE) 1.3 (0.02) 1.1 (0.01) 1.2 (0.02) 1.0 (0.02) Median Min - Max Table 14 showing the number of female subjects, teeth, and restorations recorded within the study population

113 99 Table 15. Number of Restorations by Tooth Location SSC AM All Restorations Restorations Restorations CR Restorations Tooth location for All subjects only only only Upper 1297 (49.4%) 339 (44.3%) 850 (51.5%) 107 (52.5%) Lower 1326 (50.6%) 427 (55.7%) 801 (48.5%) 97 (47.5%) Right 1323 (50.4%) 366 (47.8%) 842 (51.0%) 114 (55.9%) Left 1300 (49.6%) 400 (52.2%) 809 (49.0%) 90 (44.1%) Upper right 675 (25.7%) 170 (22.2%) 442 (26.8%) 62 (30.4%) Upper left 622 (23.7%) 169 (22.1%) 408 (24.7%) 45 (22.1%) Lower right 648 (24.7%) 196 (25.6%) 400 (24.2%) 52 (25.5%) Lower left 678 (25.8%) 231 (30.2%) 401 (24.3%) 45 (22.1%) Notes: 1. The denominator for the 'All Restorations for All Subjects' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type Table 15 showing the number of restorations by tooth location and restoration type with an equal distribution

114 100 Figure 9. Number of restorations by tooth location upper/lower demonstrating an equal distribution Figure 10. Number of restorations by tooth location left/right demonstrating an equal distribution

115 Figure 11. Number of restorations by tooth location upper/lower and left/right demonstrating an equal distribution 101

116 102 Table 16. Number of Restorations by Specific Tooth Tooth location Upper right Upper left Specific tooth All Restorations for All subjects SSC Restorations only AM Restorations only CR Restorations only (4.2%) 32 (4.2%) 67 (4.1%) 10 (4.9%) (5.6%) 48 (6.3%) 88 (5.3%) 10 (4.9%) (9.0%) 60 (7.8%) 148 (9.0%) 27 (13.2%) (6.5%) 30 (3.9%) 126 (7.6%) 15 (7.4%) (0.5%) 13 (0.8%) (4.1%) 28 (3.7%) 73 (4.4%) 6 (2.9%) (5.4%) 47 (6.1%) 86 (5.2%) 9 (4.4%) (8.2%) 65 (8.5%) 128 (7.8%) 22 (10.8%) (5.5%) 28 (3.7%) 110 (6.7%) 7 (3.4%) (0.5%) 1 (0.1%) 11 (0.7%) 1 (0.5%) Tooth location Lower right Specific tooth All Restorations for All subjects SSC Restorations only AM Restorations only CR Restorations only (2.5%) 14 (1.8%) 48 (2.9%) 3 (1.5%) (5.0%) 27 (3.5%) 97 (5.9%) 6 (2.9%) (8.7%) 92 (12.0%) 110 (6.7%) 25 (12.3%) (8.1%) 63 (8.2%) 132 (8.0%) 18 (8.8%) (0.5%) 13 (0.8%) Lower left (3.0%) 24 (3.1%) 52 (3.1%) 2 (1.0%) (5.1%) 44 (5.7%) 84 (5.1%) 5 (2.5%) (9.2%) 102 (13.3%) 118 (7.1%) 22 (10.8%) (7.7%) 61 (8.0%) 125 (7.6%) 16 (7.8%) (0.8%) 22 (1.3%) Notes: 1. The denominator for the 'All Restorations for All Subjects' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type

117 103 Figure 12. Number of restorations by specific tooth for all restoration types. The first permanent molar is the most restored tooth. Figure 13. Number of restorations by specific tooth for stainless steel crown restorations. The first permanent molar is the most restored tooth.

118 104 Figure 14. Number of restorations by specific tooth for amalgam restorations. The first and second permanent molars are the most restored teeth. Figure 15. Number of restorations by specific tooth for composite resin restorations. The first permanent molar is the most restored tooth.

119 105 Table 17. Distribution of All Restorations by Tooth Location and Male Gender SSC All Restorations Restorations AM Restorations CR Restorations Tooth location for All subjects only only only Upper 785 (48.7%) 194 (42.6%) 527 (50.8%) 64 (54.7%) Lower 826 (51.3%) 261 (57.4%) 511 (49.2%) 53 (45.3%) Right 800 (49.7%) 212 (46.6%) 525 (50.6%) 63 (53.8%) Left 811 (50.3%) 243 (53.4%) 513 (49.4%) 54 (46.2%) Upper right 403 (25.0%) 97 (21.3%) 270 (26.0%) 36 (30.8%) Upper left 382 (23.7%) 97 (21.3%) 257 (24.8%) 28 (23.9%) Lower right 397 (24.6%) 115 (25.3%) 255 (24.6%) 27 (23.1%) Lower left 429 (26.6%) 146 (32.1%) 256 (24.7%) 26 (22.2%) Notes: 1. The denominator for the 'All Restorations for All Subjects' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type Table 17 showing the number of restorations by tooth location and restoration type amongst male subjects with an equal distribution

120 106 Table 18. Distribution of All Restorations by Tooth Location and Female Gender SSC All Restorations Restorations AM Restorations CR Restorations Tooth location for All subjects only only only Upper 512 (50.6%) 145 (46.6%) 323 (52.7%) 43 (49.4%) Lower 500 (49.4%) 166 (53.4%) 290 (47.3%) 44 (50.6%) Right 523 (51.7%) 154 (49.5%) 317 (51.7%) 51 (58.6%) Left 489 (48.3%) 157 (50.5%) 296 (48.3%) 36 (41.4%) Upper right 272 (26.9%) 73 (23.5%) 172 (28.1%) 26 (29.9%) Upper left 240 (23.7%) 72 (23.2%) 151 (24.6%) 17 (19.5%) Lower right 251 (24.8%) 81 (26.0%) 145 (23.7%) 25 (28.7%) Lower left 249 (24.6%) 85 (27.3%) 145 (23.7%) 19 (21.8%) Notes: 1. The denominator for the 'All Restorations for All Subjects' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type Table 18 showing the number of restorations by tooth location and restoration type amongst female subjects with an equal distribution

121 107 Table 19. Number of Censored Observations Including All Restoration Types Censoring Pre-existing All restorations No 1664 (63.5%) SSC restorations AM restorations CR restorations 650 (84.9%) 1011 (61.2%) 3 (1.5%) Yes 957 (36.5%) 116 (15.1%) 640 (38.8%) 201 (98.5%) Failed* by end of study No 1738 (66.3%) 675 (88.1%) 979 (59.3%) 84 (41.2%) Yes 883 (33.7%) 91 (11.9%) 672 (40.7%) 120 (58.8%) Censoring Pre-existing restorations intact at end of study (censored) Pre-existing restorations that failed* before end of study period (censored) New restorations intact at end of study (censored) Completed longevities (uncensored) 517 (19.7%) 95 (12.4%) 340 (20.6%) 82 (40.2%) 440 (16.8%) 21 (2.7%) 300 (18.2%) 119 (58.3%) 1221 (46.6%) 580 (75.7%) 639 (38.7%) 2 (1.0%) 443 (16.9%) 70 (9.1%) 372 (22.5%) 1 (0.5%) Notes: 1. The denominator for the 'All Restorations' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type * 'Failed' indicates that the restoration was removed/replaced/ceased to exist

122 108 Table 20: Distribution of Diagnoses for the Placement of SSC and Amalgam Restorations Restoration Placed SSC Amalgam Diagnosis Number Percentage (/650) Number Percentage (/1011) Caries Pre-existing restoration (Inadequate) Pre-existing SSC (Inadequate) Loose/Lost SSC SSC Perforation Tooth Fracture Restoration Fracture Loose/Lost Restoration Pulpal Pathology/Necrosis Periodontal disease

123 Figure 16. Number of failures recorded by the end of study from all restoration types (combined pre-existing and new restorations) 109

124 110 Table 23. Distribution of SSC Occlusal Perforations Replaced with New Repaired Occlusal Total Diagnosis SSC Perforation of SSC with AM (/766) Number Percent SSC Perforation 12 17* Note: *The 17 SSCs that were repaired with occlusal amalgam restorations were not considered conventional amalgam restorations nor a failure of the SSCs, as the crown remained intact with sealed margins, in the absence of recurrent decay or pathology.

125 111 Table 24. Diagnoses for Specific Amalgam Restoration Failures Replaced with a New Restoration New Replacement Restoration AM AM Total Diagnosis (Same Extent) (Greater Extent) SSC Number Percentage (/434) Caries Tooth Fracture Restoration Fracture Pre-existing Restoration (Inadequate) Pre-existing SSC (Inadequate) Total

126 112 Table 27. Diagnoses for Composite Resin Restoration Failures Replaced with New Restorations Replacement Restoration CR Total Diagnosis (Same Extent) AM SSC Number Percentage (/94) Caries Loose/Lost Restoration Tooth Fracture Restoration Fracture Pre-existing restoration (Inadequate) Pre-existing SSC (Inadequate) Pulpal pathology/ Necrosis Periodontal disease Total

127 113 Table 28. Number and Distribution of All New Restorations Censoring Pre-existing All restorations SSC restorations AM restorations CR restorations No 1664 (100.0%) 650 (100.0%) 1011 (100.0%) 3 (100.0%) Failed* by end of study No 1221 (73.4%) 580 (89.2%) 639 (63.2%) 2 (66.7%) Yes 443 (26.6%) 70 (10.8%) 372 (36.8%) 1 (33.3%) Censoring New restorations intact at end of study (censored) Completed longevities (uncensored) 1221 (73.4%) 580 (89.2%) 639 (63.2%) 2 (66.7%) 443 (26.6%) 70 (10.8%) 372 (36.8%) 1 (33.3%) Notes: 1. The denominator for the 'All Restorations' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type * 'Failed' indicates that the restoration was removed/replaced/ceased to exist

128 Figure 17. Non-censored number and distribution of new restoration failures. 114

129 115 Table 29. Distribution and Number of All Pre-existing Restorations Censoring Pre-existing All restorations SSC restorations AM restorations CR restorations Yes 957 (100.0%) 116 (100.0%) 640 (100.0%) 201 (100.0%) Failed* by end of study No 517 (54.0%) 95 (81.9%) 340 (53.1%) 82 (40.8%) Yes 440 (46.0%) 21 (18.1%) 300 (46.9%) 119 (59.2%) Censoring Pre-existing restorations intact at end of study (censored) Pre-existing restorations that failed* before end of study period (uncensored) 517 (54.0%) 95 (81.9%) 340 (53.1%) 82 (40.8%) 440 (46.0%) 21 (18.1%) 300 (46.9%) 119 (59.2%) Notes: 1. The denominator for the 'All Restorations' column is the total number of restorations of any type 2. The denominator for other columns is the total number of restorations of that type * 'Failed' indicates that the restoration was removed/replaced/ceased to exist

130 Figure 18. Number of failures by end of study for all pre-existing restorations 116

131 117 Table 31. Product-Limit Estimate of Longevity for All Stainless Steel Crown Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** Yearly estimates (percent incomplete) # With complete info on longevity # With incomplete info on longevity 0 year(s) 100.0% year(s) 98.7% (0.6%) (98.7%, 98.7%) year(s) 97.6% (1.1%) (97.6%, 97.7%) year(s) 97.1% (1.2%) (97.0%, 97.1%) year(s) 95.2% (2.0%) (95.0%, 95.4%) year(s) 93.8% (2.7%) (93.4%, 94.1%) year(s) 91.2% (7.1%) (89.9%, 92.3%) year(s) 89.4% (7.7%) (87.8%, 90.8%) year(s) 82.6% (11.5%) (78.8%, 85.9%) year(s) 79.6% (14.1%) (74.0%, 84.1%) year(s) 78.7% (15.1%) (72.5%, 83.7%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

132 Figure 19. Survival curve and 95% CI for all stainless steel crown restorations (combined pre-existing and new) 118

133 119 Table 32. Product-Limit Estimate of Longevity for New Stainless Steel Crown Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** # Failed # Intact Yearly estimates (percent intact) 0 year(s) 100.0% year(s) 98.5% (0.7%) (98.5%, 98.5%) year(s) 97.2% (1.3%) (97.1%, 97.3%) year(s) 96.5% (1.5%) (96.4%, 96.6%) year(s) 94.4% (2.5%) (94.1%, 94.6%) year(s) 92.7% (3.4%) (92.2%, 93.2%) year(s) 89.7% (8.5%) (87.9%, 91.2%) year(s) 87.5% (9.4%) (85.2%, 89.5%) year(s) 79.2% (15.4%) (73.0%, 84.2%) year(s) 75.4% (19.8%) (66.0%, 82.5%) year(s) 74.2% (21.7%) (63.3%, 82.2%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

134 Figure 20. Survival curve and 95% CI for new stainless steel crown restorations (that were placed at MSH) 120

135 121 Table 33. Product-Limit Estimate of Longevity for Pre-existing Stainless Steel Crown Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** # Failed # Intact Yearly estimates (percent intact) 0 year(s) 100.0% year(s) 96.4% (4.3%) (96.1%, 96.7%) year(s) 96.4% (4.3%) (96.1%, 96.7%) year(s) 96.4% (4.3%) (96.1%, 96.7%) year(s) 96.4% (4.3%) (96.1%, 96.7%) year(s) 94.9% (4.5%) (94.4%, 95.3%) year(s) 93.2% (4.6%) (92.6%, 93.8%) year(s) 91.4% (5.0%) (90.6%, 92.2%) year(s) 87.0% (6.3%) (85.4%, 88.4%) year(s) 79.1% (13.1%) (73.9%, 83.5%) year(s) 73.4% (19.2%) (63.7%, 80.9%) year(s) 65.8% (13.7%) (57.9%, 72.7%) year(s) 61.1% (12.8%) (53.2%, 68.2%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

136 Figure 21. Survival curve and 95% CI for pre-existing stainless steel crown restorations (present at time of new patient exam at MSH) 122

137 123 Table 34. Follow-up by Subject and by Restoration Type for All Restorations Follow-up (years) Category All subjects SSCs only AMs only CRs only Subject N 271 Mean (SE) (0.518) Median (IQR) ( ) Min - Max Restoration N Mean (SE) 7.97 (0.088) 6.11 (0.110) 9.27 (0.121) 4.43 (0.142) Median (IQR) 5.61 ( ) 5.09 ( ) 6.90 ( ) 2.31 ( ) Min - Max Follow-up=0 years N (%) Follow-up>0 years N (%) 46 (1.8%) 27 (3.5%) 19 (1.2%) 0 (0.0%) 2575 (98.2%) 739 (96.5%) 1632 (98.8%) 204 (100.0%) Restorations with Follow-up Time>0 N Mean (SE) 8.11 (0.089) 6.34 (0.106) 9.38 (0.122) 4.43 (0.142) Median (IQR) 5.71 ( ) 5.23 ( ) 7.05 ( ) 2.31 ( ) Min - Max

138 Figure 22. Follow-up time in 5-year increments by subject. Zero follow up is for patients where the date of their treatment coincided with their most recent appointment at MSH. 124

139 Figure 23. Follow-up time in 5-year increments by restoration type for all restorations. Zero follow up is for patients where the date of their treatment coincided with their most recent appointment at MSH. 125

140 126 Table 35. Product-Limit Estimate of Longevity for All Amalgam Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** Yearly estimates (percent incomplete) # With complete info on longevity # With incomplete info on longevity 0 year(s) 100.0% year(s) 98.6% (0.7%) (98.6%, 98.6%) year(s) 95.9% (3.7%) (95.6%, 96.2%) year(s) 92.6% (4.2%) (92.0%, 93.2%) year(s) 90.0% (4.7%) (89.0%, 90.8%) year(s) 87.2% (5.3%) (85.9%, 88.4%) year(s) 84.8% (10.3%) (81.7%, 87.4%) year(s) 81.1% (10.7%) (77.2%, 84.4%) year(s) 76.9% (11.4%) (72.0%, 81.1%) year(s) 72.5% (12.9%) (66.1%, 78.0%) year(s) 70.7% (13.7%) (63.5%, 76.7%) year(s) 66.8% (16.0%) (57.6%, 74.5%) year(s) 64.7% (17.3%) (54.3%, 73.3%) year(s) 62.0% (19.4%) (49.7%, 72.1%) year(s) 54.9% (23.7%) (38.5%, 68.7%) year(s) 53.5% (25.2%) (35.9%, 68.3%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

141 Figure 24. Survival curve and 95% CI for all amalgam restorations (combined preexisting and new) 127

142 128 Table 36. Product-Limit Estimate of Longevity for New Amalgam Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** # Failed # Intact Yearly estimates (percent intact) 0 year(s) 100.0% year(s) 97.7% (1.1%) (97.7%, 97.8%) year(s) 93.4% (5.7%) (92.7%, 94.1%) year(s) 88.2% (6.3%) (86.8%, 89.5%) year(s) 84.0% (6.9%) (81.9%, 85.8%) year(s) 79.6% (7.6%) (76.7%, 82.2%) year(s) 75.8% (13.6%) (69.6%, 80.8%) year(s) 70.0% (13.4%) (62.9%, 76.0%) year(s) 63.5% (13.1%) (55.7%, 70.4%) year(s) 56.5% (13.4%) (47.6%, 64.5%) year(s) 53.4% (13.9%) (43.9%, 62.0%) year(s) 47.0% (15.7%) (35.8%, 57.4%) year(s) 43.6% (16.9%) (31.5%, 55.1%) year(s) 39.1% (20.4%) (24.6%, 53.3%) year(s) 28.9% (30.7%) (10.4%, 50.7%) year(s) 27.1% (33.7%) (8.0%, 51.0%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

143 Figure 25. Survival curve and 95% CI for new amalgam restorations (that were placed at MSH) 129

144 130 Table 37. Product-Limit Estimate of Longevity for Pre-existing Amalgam Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** # Failed # Intact Yearly estimates (percent intact) 0 year(s) 100.0% year(s) 88.6% (10.0%) (86.3%, 90.5%) year(s) 85.6% (11.3%) (82.4%, 88.3%) year(s) 81.0% (13.2%) (76.1%, 85.0%) year(s) 78.5% (14.0%) (72.8%, 83.2%) year(s) 74.2% (15.9%) (66.5%, 80.4%) year(s) 71.1% (17.4%) (61.9%, 78.5%) year(s) 67.2% (19.6%) (55.7%, 76.3%) year(s) 63.6% (21.6%) (50.1%, 74.3%) year(s) 59.4% (24.7%) (43.0%, 72.6%) year(s) 57.4% (26.3%) (39.5%, 71.8%) year(s) 54.4% (29.3%) (33.9%, 71.0%) year(s) 50.6% (29.6%) (29.6%, 68.2%) year(s) 48.7% (31.3%) (26.5%, 67.7%) year(s) 41.1% (35.5%) (16.8%, 64.2%) year(s) 37.1% (39.9%) (11.4%, 63.5%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

145 Figure 26. Survival curve and 95% CI for pre-existing amalgam (present at time of new patient exam at MSH) 131

146 132 Table 38. Product-Limit Estimate of Longevity for Pre-existing Composite Resin Restorations Product-limit estimate of longevity Estimate (SE*) 95% CI** # Failed # Intact Yearly estimates (percent incomplete) 0 year(s) 100.0% year(s) 67.9% (32.1%) (48.3%, 81.3%) year(s) 58.4% (30.9%) (37.4%, 74.6%) year(s) 52.5% (30.8%) (30.8%, 70.3%) year(s) 46.9% (30.8%) (25.0%, 66.1%) year(s) 44.6% (30.9%) (22.8%, 64.4%) year(s) 42.2% (31.7%) (20.0%, 62.9%) year(s) 38.1% (33.4%) (15.6%, 60.5%) year(s) 37.0% (34.3%) (14.3%, 60.2%) year(s) 33.7% (35.8%) (11.1%, 58.3%) year(s) 33.7% (35.8%) (11.1%, 58.3%) year(s) 31.1% (39.9%) (7.8%, 58.6%) year(s) 31.1% (39.9%) (7.8%, 58.6%) year(s) 31.1% (39.9%) (7.8%, 58.6%) year(s) 23.3% (33.8%) (5.9%, 47.2%) year(s) 15.5% (23.2%) (5.3%, 30.7%) Note: * Williams estimate of standard error ** Based on Williams estimate of standard error

147 Figure 27. Survival curve and 95% CI for pre-existing composite resin restorations (present at time of new patient exam at MSH) 133

148 Figure 28. Survival curve comparison between all amalgam and SSC restorations demonstrating the superiority of the SSC restoration 134

149 Table 39. Product-Limit Estimate of Longevity of New Stainless Steel Crown Restorations by Age Group 135

150 Figure 31. Survival of new stainless steel crown restorations by different age groups at time of placement 136

151 Table 40: Product-Limit Estimate of Longevity of New Amalgam Restorations by Age Group 137

152 Figure 32. Survival of new amalgam restorations by different age groups at time of placement demonstrating a negligible difference 138

153 139 Table 41. Product-Limit Estimate of Longevity of New SSC Restorations by Gender Year Yearly estimates (percent intact) Male PL Estimate Failed Intact Female PL Estimate Failed Intact 0 year(s) 100.0% % year(s) 99.2% % year(s) 98.3% % year(s) 97.9% % year(s) 96.4% % year(s) 94.6% % year(s) 91.7% % year(s) 90.3% % year(s) 80.3% % 29 42

154 Figure 33. Survival of new SSC restorations by gender demonstrating a negligible difference 140

155 141 Table 42. Product-Limit Estimate of Longevity of New Amalgam Restorations by Gender Male Female Year PL Estimate Failed Intact PL Estimate Failed Intact Yearly estimates (percent intact) 0 year(s) 100.0% % year(s) 98.4% % year(s) 93.3% % year(s) 86.7% % year(s) 83.1% % year(s) 78.3% % year(s) 73.9% % year(s) 68.2% % year(s) 62.7% %

156 Figure 34. Survival of new amalgam restorations by gender demonstrating a negligible difference 142

157 Table 43. Product-Limit Estimate of Longevity of New SSC Restorations by Location (Upper vs. Lower) 143

158 Figure 35. Survival of new SSC restorations by location (upper vs. lower) of placement demonstrating a negligible difference 144

159 Table 44. Product-Limit Estimate of Longevity of New Amalgam Restorations by Location (Upper vs. Lower) 145

160 Figure 36. Survival of new amalgam restorations by location (upper vs. lower) of placement demonstrating a negligible difference 146

161 147 Table 45. Crude Success Rates for New SSC and Amalgam Restorations Category SSC AM Number of restorations Number of failed restorations Number of intact restorations Crude success rate (SE*) 89.2% (1.00%) 63.2% (1.35%) Note: *takes into account correlations Figure 37. Crude success rates for new SSC and amalgam restorations

162 148 Table 47. Duration Between Pre and Post SSC Periapical Radiographs Statistic Category N Mean SE Median Min Max Accounting for Correlations

163 APPENDIX 1: DEMOGRAPHICS A) Screenshots of Database for Appendix 1 Data Collection 149

164 150 B) Patient Demographics 1. MRN/MSID: 9 digits 2. DOB: (YYYY-MM-DD) 3. Gender: (Male or Female) 4. Date of Most Recent Visit: (YYYY-MM-DD) 5. Date of Initial Visit to MSH: (YYYY-MM-DD) 6. Referred by: Family DDS = 1 Family MD/ Institution MD = 2 Primary Caregiver = 3 Social services/ health unit = 4 Other = 5 7. Type of Residence: On own (alone) = 1 On own with attendant care (24/7) = 2 Family/Foster Home = 3 Group Home = 4 Institution/Chronic Care Facility = 5 Other = 6 Unknown = 7 C) Family History 1. Heart Problems: No = 0; Yes = 1 2. Bleeding Problems: No = 0; Yes = 1

165 Diabetes: No = 0; Yes = 1 4. Hypertension: No = 0; Yes = 1 5. Malignant Hyperthermia (MH): No = 0; Yes = 1 6. Cancer: No = 0; Yes = 1 7. Developmental Disability: No = 0; Yes = 1 8. Other: (State) D) Medical Information i) Central Nervous System 1. ADD/ADHD/Autism (unspecified) (No = 0, Yes = 1) 2. ADD (specified) (No = 0, Yes = 1) 3. ADHD (specified) (No = 0, Yes = 1) 4. Autism (specified) (No = 0, Yes = 1) 5. Alzheimer s Disease/Dementia (No = 0, Yes = 1) 6. Cerebral Palsy (No = 0, Yes = 1) 7. Cerebral Vascular Accident (CVA/Stroke) (No = 0, Yes = 1) 8. Craniofacial Anomaly (No = 0, Yes = 1) 9. Cognitive impairment (ex. Memory/concentration) (No = 0, Yes = 1) 10. Developmental Delay (No = 0, Yes = 1) 11. Down s Syndrome (No = 0, Yes = 1) 12. Facial pain disorders (No = 0, Yes = 1) 13. Fainting spells (No = 0, Yes = 1) 14. Hearing disorder (No = 0, Yes = 1) 15. Malignant hyperthermia (No = 0, Yes = 1) - Number of Malignant Hyperthermia Attacks (enter value)

166 Mental Retardation (No =0, Yes but Unspecified=1) (If Classified: Mild=2, Moderate=3, Severe/profound=4) 17. Migraine or Recurring headaches (No = 0, Yes = 1) 18. Multiple Sclerosis (No = 0, Yes = 1) 19. Muscular Dystrophy (No = 0, Yes = 1) 20. Parkinson s disease (No = 0, Yes = 1) 21. Psychiatric disorder (No = 0, Yes = 1) 22. Seizures/Epilepsy (No = 0, Yes = 1) 23. Sight disorder (not correctable with glasses) (No = 0, Yes = 1) 24. Sleep problems (No = 0, Yes = 1) 25. Spina Bifida (No = 0, Yes = 1) 26. Traumatic/Acquired Head or Brain injury (No =0, Yes =1) - Has Shunt (No = 0, Yes=1) 27. Other: (Enter words) ii) Cardiovascular System 1. Anemia (No = 0, Yes = 1) 2. Angina/chest pains (No = 0, Yes = 1) 3. Artificial/prosthetic heart value or artery/vein (No = 0, Yes = 1) 4. Bleeding or clotting disorder (No = 0, Yes but Unspecified= 1) - If Specified: (Hemophilia = 2, Sickle Cell Anemia = 3, Thalassemia = 4, Other = 5) 5. Prolonged bleeding (ex. After cut or extraction) (No = 0, Yes = 1) 6. Blood clots in legs or other blood vessels (Deep vein thrombosis) (No = 0, Yes = 1) 7. Easy bruising (No = 0, Yes = 1)

167 Congenital heart disease (Unspecified) (No = 0, Yes = 1) - If specified: (select all that apply) VSD = (No = 0, Yes = 1) ASD = (No = 0, Yes = 1) Tetrology of Fallot = (No = 0, Yes = 1) Mitral valve prolapse = (No = 0, Yes = 1) Eisenmenger s Complex = (No = 0, Yes = 1) Other = (No = 0, Yes = 1) 9. Congestive heart failure (No = 0, Yes = 1) 10. Cyanosis (No = 0, Yes = 1) 11. Pacemaker (No = 0, Yes = 1) 12. History of a blood or blood product transfusion (No = 0, Yes = 1) 13. Heart attack (No = 0, Yes = 1) 14. Heart surgery (No = 0, Yes = 1) 15. High or low blood pressure (Unspecified) (No = 0, Yes = 1) 16. High blood pressure (specified) (No = 0, Yes = 1) 17. Low blood pressure (specified) (No = 0, Yes = 1) 18. Irregular pulse or heartbeat (No = 0, Yes = 1) 19. Limits to walking/work/exercise/sports (No = 0, Yes = 1) 20. Rheumatic fever (known history of disease) (No = 0, Yes = 1) 21. Other: (Enter words) iii) Respiratory System 1. Asthma (No = 0, Yes = 1) 2. Collapsed lung (No = 0, Yes = 1)

168 Smoker (No = 0, Yes = 1) a) What do you smoke: (Select all that apply) i. Cigarettes = No = 0; Yes = 1 ii. Cigars = No = 0; Yes = 1 iii. Marijuana = No = 0; Yes = 1 iv. Pipes = No = 0; Yes = 1 v. Other = No = 0; Yes = 1 b) How much do you smoke (packs/day) (Enter value from 1-100) c) For how long have you smoked (pack years) (Enter value from 1-100) 4. Emphysema (No = 0, Yes = 1) 5. Nasal or sinus problems (No = 0, Yes = 1) 6. Pneumonia (No = 0, Yes = 1) 7. Pulmonary embolus/blood clot (No = 0, Yes = 1) 8. Shortness of breath (No = 0, Yes = 1) 9. Sleep apnea (No = 0, Yes = 1) 10. Tuberculosis (TB) (No = 0, Yes = 1) 11. Other: (Enter words) iv) Gastrointestinal System 1. Cannot take aspirin (No = 0, Yes = 1) 2. Dysphagia/Swallowing problem (No = 0, Yes = 1) 3. G or J Tube (No = 0, Yes = 1) 4. GERD (No = 0, Yes = 1) 5. Hepatitis/jaundice (No = 0, Yes = 1) 6. Hiatus hernia (No = 0, Yes = 1)

169 Intestinal or bowel disorders (No = 0, Yes = 1) 8. Irritable bowel syndrome (No = 0, Yes = 1) 9. Liver disease (No = 0, Yes = 1) 10. Recurring mouth ulcers (No = 0, Yes = 1) 11. Stomach/intestinal ulcers (No = 0, Yes = 1) 12. Upset stomach or diarrhea when taking medications (No = 0, Yes = 1) 13. Other: (Enter words) v) Immune System 1. Allergies (No = 0, Yes = 1) Medications (No = 0, Yes = 1) Environmental Allergies (No = 0, Yes = 1) Dietary Allergies (No = 0, Yes = 1) Antibiotic Allergies (No = 0, Yes = 1) Local anesthetic allergies (No = 0, Yes = 1) Other allergies (Enter words) 2. Cancer (No = 0, Yes = 1) 3. Chromosome/Genetics Disorder (No = 0, Yes = 1) 4. Crohn s disease (No = 0, Yes = 1) 5. HIV/AIDs (No = 0, Yes = 1) 6. Metabolic disorders (No = 0, Yes = 1) 7. Rheumatoid /Osteoarthritis/ Arthritis (No = 0, Yes = 1) 8. Other (Enter words)

170 156 vi) Genito-Urinary System 1. Bladder problems (No = 0, Yes = 1) 2. Dialysis (No = 0, Yes but Unspecified = 1) Hemodialysis (specified) (No = 0, Yes = 1) Peritoneal (specified) (No = 0, Yes = 1) 3. Prostate problems (No = 0, Yes = 1) 4. Renal problems (No = 0, Yes = 1) 5. Urinary tract problems (No = 0, Yes = 1) 6. Other (Enter words) vii) Endocrine System 1. Diabetes (No =0, Yes but Unspecified=1, Type 1 (insulin dependent)=2, Hypoglycemic medications = 3, Diet controlled =4) - Number of diabetic hospitalizations: (Enter value) 2. Hormone problems (No = 0, Yes = 1) 3. Pituitary problems (No = 0, Yes = 1) 4. Thyroid problems (No = 0, Yes but Unspecified = 1, Hypothyroid = 2, Hyperthyroid = 3) 5. Other: (Enter words) viii) Musculoskeletal System 1. Taking medications to increase bone density (No = 0, Yes = 1) 2. Artificial/prosthetic joint (No = 0, Yes = 1) 3. Jaw joint problems (No = 0, Yes = 1) 4. Osteoporosis (No = 0, Yes = 1) 5. Physical impairment/disability/ Wheelchair bound (No = 0, Yes = 1)

171 Quadriplegia/Paraplegia or Paresis (unspecified) (No = 0, Yes = 1) Quadriplegia/paresis (specified) (No = 0, Yes = 1) Paraplegia/paresis (specified) (No = 0, Yes = 1) 7. Scoliosis (No = 0, Yes = 1) 8. Other: (Enter words) ix) Dermatology 1. Skin lesions/disorders (No = 0, Yes = 1) 2. Allergy/Hives/Rashes (unspecified) (No = 0, Yes = 1) Hives (specified) (No = 0, Yes = 1) Rashes (specified) (No = 0, Yes = 1) 3. Other (Enter words) E) Medications at the Present Time *Date of data entry 1. Any Medications: No = 0; Yes = 1 2. Analgesics: (No = 0; Yes = 1) (Select all that apply) ASA = No = 0; Yes = 1 Acetaminophen = No = 0; Yes = 1 NSAIDS = No = 0; Yes = 1 Narcotics/opioids = No = 0; Yes = 1 Other = No = 0; Yes = 1 3. Antacids /H2 blockers: No = 0; Yes = 1 4. Antibiotics (Daily, acute infection or prophylactically): No = 0; Yes = 1 5. Anticoagulants: No = 0; Yes = 1 6. Antihypertensives: No = 0; Yes = 1

172 Bisphosphonates: (No = 0, Yes = 1) - If route provided: (Intravenous = 2, Oral = 3) 8. Blood Transfusions: No = 0; Yes = 1 9. Cortisone/Steroids: No = 0; Yes = Diuretics: No = 0; Yes = Generic cardiac medications: No = 0; Yes = Hormone Replacement Therapy: No = 0; Yes = Inhalers (Ventolin, etc.): No = 0; Yes = Laxatives: No = 0; Yes = Muscle Relaxants: No = 0; Yes = Psychotropic Medications: No = 0; Yes = Seizure Medications: No = 0; Yes = Thyroid Medications: No = 0; Yes = Other: (Enter words) F) Previous Surgical Experience 1. Total number of dental general anesthetics: (enter numerical value) 2. Teeth present as recorded during Dental General Anaesthetic Treatments (from Odontogram) for respective treatment dates G) Dental Information 1. Dental coverage: (Select all that apply) No Insurance = No = 0; Yes = 1 ODSP = No = 0; Yes = 1 Community/Social Services/Ontario Works = No = 0; Yes = 1

173 159 Private Insurance = No = 0; Yes = 1 New Refugee Status = No = 0; Yes = 1 Welfare = No = 0; Yes = 1 Reserve/Native Status = No = 0; Yes = 1 Other = No = 0; Yes = 1 2. From Initial New Patient Exam (Intraoral findings) a) Occlusion: Not stated/unknown = 0 Class 1 Molar = 1 Class 2 Molar = 2 Class 3 Molar = 3 b) Overbite (%): (Fill in value or leave blank if not noted) c) Anterior open bite: (No = 0; Yes = 1) d) Overjet (mm): (Fill in numerical value or leave blank if not noted) e) Parafunction/Bruxism: (No = 0; Yes = 1) f) Other significant findings: (Fill in text box) 3. Caries Risk at Initial Exam: Low = 1 Moderate = 2 High = 3 4. Oral Hygiene Status at Initial Exam: Poor (severe generalized plaque accumulation) = 0

174 160 Fair (moderate generalized plaque accumulation) = 1 Good (minimal generalized plaque accumulation) = 2 Excellent = 3 5. Number of teeth present at initial new patient exam: (Fill in numerical value) 6. Outpatient Clinic Restorative treatment currently performed by: (Select all that apply) Staff: No = 0; Yes = 1 Post-graduate student: No = 0; Yes = 1 Residents/interns: No = 0; Yes = 1 Undergraduate Dental Students: No = 0; Yes = 1 7. Outpatient Hygiene/Cleanings currently performed by: (Select all that apply) Staff: No = 0; Yes = 1 Post-graduate student: No = 0; Yes = 1 Residents/interns: No = 0; Yes = 1 Undergraduate Dental Students/ D-Clinic: No = 0; Yes = 1 Hygienist: No = 0; Yes = 1 8. Inpatient GA treatments performed by: (2 options) i. Staff, Resident/intern, and Post-graduate student: No = 0; Yes = 1 ii. Staff and Resident/intern: No = 0; Yes = 1 9. Outpatient GA treatments performed by: (2 options) i. Staff, Resident/intern and Post-graduate student: No = 0; Yes = 1

175 161 ii. Staff and Resident/intern: No = 0; Yes = All treatment conducted at MSH for Patient: (select all that apply) i) Examination: No = 0; Yes = 1 ii) Radiographs: No = 0; Yes = 1 iii) Preventive: No = 0; Yes = 1 iv) Restorative: No = 0; Yes = 1 v) Endodontics: No = 0; Yes = 1 vi) Surgical: No = 0; Yes = 1 vii) Prosthetic: No = 0; Yes = 1 viii) Adjunctive periodontal therapy: No = 0; Yes = 1 ix) Other: No = 0; Yes = Frankl Scale of Behaviour/Cooperation (Recorded at Initial new patient exam) i) Definitely Negative (-- or greater) (Refusal of treatment/extreme negativism/violent) = 1 ii) Negative (-)(Reluctance to accept treatment, uncooperative) = 2 iii) Positive (+)(Acceptance of tx, cautious, needs help) = 3 iv) Definitely Positive (++ or greater) (Good cooperation, with ease) = Recall Program (Most recent that is recorded) Not stated = 0 3 months = 1 6 months = 2 12 months = 3

176 162 APPENDIX 2: DENTAL TREATMENT DATABASE A) Screenshots of Database for Appendix 2 Data Collection

177 163 B) Dental Treatment Data Collection 1) Tooth Number *Must fill in either field 2 or 3 for every data entry 2) Pre-existing Restoration or SSC: Date of Initial new patient exam (YYYY/MM/DD) OR For final assessment of SSC or Restoration: Date of most recent recall/dental examination (YYYY/MM/DD) 3) Date of Dental Treatment (new) conducted: (YYYY/MM/DD) 4) Dental Diagnosis: Caries: 1 Pre-existing Restoration: 2 Pre-existing SSC: 3 Loose/Lost Restoration: 4 Loose/Lost SSC: 5 SSC Perforation: 6 Tooth Fracture: 7 Restoration Fracture: 8 Pulpal Pathology/Necrosis: 9 Other: + 4) Surfaces Restored (Available for All Dental Treatments) Not Applicable/Unknown = A Buccal (B) = B

178 164 Lingual (L) = C Occlusal (O) = D Occlusal-Lingual (OL) = E Occlusal -Buccal (OB) = F Mesial-Occlusal (MO) = G Disto-Occlusal (DO)= H Mesial-Occlusal- Distal (MOD) = I Mesial-Occlusal- Buccal (MOB) = J Mesial- Occlusal Lingual (MOL) = K Mesial- Occlusal Lingual Buccal (MOLB) = L Disto- Occlusal- Buccal (DOB) = M Disto- Occlusal- Lingual (DOL) = N Disto-Occlusal Lingual Buccal (DOLB) = O Mesial-Occlusal-Distal-Lingual (MODL) = P Mesial- Occlusal- Distal- Buccal (MODB) = Q Mesial- Occlusal Distal- Buccal Lingual (MODBL) = R Recurrent = S 5) Type of Dental Treatment No treatment needed = 0 Composite resin restoration (CR) = 1 Amalgam restoration (AM) = 2 Stainless steel crown (SSC) = 3 Glass ionomer filling (GIC) = 4 Extraction = 5

179 165 6) How treatment was conducted: Not Applicable = 0 No Local anesthetic (LA), N 2 O or Sedation = 1 Local anesthetic only (LA) = 2 Local anesthetic and Nitrous oxide (N 2 O) = 3 Local anesthetic and oral sedation = 4 General anesthetic (GA) = 5 Unknown/Other = 6 7) Status of Pre-existing Restoration Unknown (Pre-existing) = 0 Intact/ Within Normal Limits = 1 Non-restored (virgin) tooth = 2 New/Original (different site of tooth) = 3 Defect (Monitored and No treatment required) = 4 Repair (defect requires repair within restoration) = 5 Recementation of SSC = 6 Replacement of restoration (EXACT same material and extent*also classified as Failure) = 7 Failure (GREATER extent, different material, new SSC, RCT or Extraction)= 8 8) Final assessment (most recent recall, etc.) of Restoration Not Applicable = 0 No treatment required = 1

180 166 Treatment required = 2 Left blank = d

181 167 APPENDIX 3: RADIOGRAPHIC ASSESSMENT DATABASE A) Screenshots of Database for Appendix 3 Data Collection

182 168 B) Radiographic Assessment Data Collection a) Date of Dental Treatment: (YYYY-MM- DD) b) Pre or Post SSC: Pre = 0 Post = 1 c) Tooth with SSC: (Select tooth number) d) Type of Radiograph: Bitewing = 1 Periapical = 2 e) From bitewing radiographs: Alveolar Bone Measurement i) Measurement recorded of alveolar bone status (Distal to SSC) a) Site distal to SSC: (fill in numerical value to 2nd decimal point) b) Normal or Non-Resorbed (<2mm)= 0 Resorbed (>2mm) = 1 Not Applicable = 2 ii) Measurement recorded of alveolar bone status (Mesial to SSC) a) Site mesial to SSC: (fill in numerical value to 2nd decimal point) b) Normal or Non-Resorbed (<2mm)= 0 Resorbed (>2mm) = 1 Not Applicable = 2 e) Subsample Study: Periapical index score (PAI) (1-5) - Periapical radiograph and PAI assessment of tooth prior to SSC restoration

183 169 - PAI assessment of tooth at a time point following SSC restoration 0 = Cannot be determined (No PA film or view available) 1 = Normal periapical structure (healthy) 2 = Small changes in bone structure (mild inflammation/pdl widening) 3 = Changes in bone structure with some mineral loss 4 = Periodontitis with well-defined radiolucent area 5 = Severe periodontitis with exacerbating features 6 = Not Applicable

184 170 APPENDIX 4: PERIAPICAL INDEX REFERENCE Reference Radiographs/Line Drawings with Periapical Index (PAI) Scores (Trope, 1999: Reproduced with permission from the Swedish Dental Journal, 1967) Fig./. Reference radiographs, corresponding line drawings and their associated scores. (Orstavik, 1986)