Esposito M, Worthington HV, Thomsen P, Coulthard P

Transcription

1 Interventions for replacing missing teeth: dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous Esposito M, Worthington HV, Thomsen P, Coulthard P This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published in The Cochrane Library 00, Issue 3 1

2 T A B L E O F C O N T E N T S ABSTRACT SYNOPSIS BACKGROUND OBJECTIVES CRITERIA FOR CONSIDERING STUDIES FOR THIS REVIEW SEARCH STRATEGY FOR IDENTIFICATION OF STUDIES METHODS OF THE REVIEW DESCRIPTION OF STUDIES METHODOLOGICAL QUALITY RESULTS DISCUSSION AUTHORS CONCLUSIONS POTENTIAL CONFLICT OF INTEREST ACKNOWLEDGEMENTS SOURCES OF SUPPORT REFERENCES GRAPHS AND OTHER TABLES INDEX TERMS COVER SHEET i

3 Interventions for replacing missing teeth: dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous Esposito M, Worthington HV, Thomsen P, Coulthard P This record should be cited as: Esposito M, Worthington HV, Thomsen P, Coulthard P. Interventions for replacing missing teeth: dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous maxilla. The Cochrane Database of Systematic Reviews 003, Issue. Art. No.: CD DOI: /14188.CD This version first published online: April 003 in Issue, 003. Date of most recent substantive amendment: 3 February 003 A B S T R A C T Background Dental implants are used for replacing missing teeth. However, the possibility of placing dental implants is limited by the presence of adequate bone volume permitting their anchorage. Several bone grafting procedures have been developed to solve this problem. The missing bone can be taken from a donor site, transplanted where needed and then implants are placed. Major bone grafting operations have to be undertaken under general anaesthesia and patients have to be hospitalized for a few days. Some degree of morbidity related to the donor site must be expected and two to three surgical interventions are needed before the implants can be functionally used. Often patients have to wait more than 1 year before a denture can be fixed to the implants and the total cost of the treatment is high. However, the major problem is that about % of the implants placed in grafted bone fail. Zygomatic implants are long screw-shaped implants developed as an alternative to bone grafting. Zygomatic implants are inserted into the body of the zygomatic bone. Their main advantages are that bone grafting may not be needed and patients may be fitted with a fixed denture much sooner. Objectives To test the hypothesis of no difference in outcomes between zygomatic implants without bone augmenting procedures in comparison with conventional dental implants in augmented bone for severely resorbed maxillae. Search strategy We searched the Cochrane Oral Health Group s Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. We handsearched several dental journals. No language restrictions were applied. Personal contacts and manufacturers of dental implants were contacted to identify unpublished trials. Most recent search: February 003. Selection criteria Randomised controlled clinical trials (RCTs) on patients with severely resorbed maxillae who could not be rehabilitated with conventional dental implants, treated with zygomatic implants without bone grafts versus conventional dental implants with bone grafts or other procedures for bone augmentation with a follow up of at least 1 year. Outcome measures considered were: prosthesis and implant failures, side effects, patient satisfaction and cost effectiveness. Data collection and analysis Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were to be conducted in duplicate and independently by two reviewers. Results were to be expressed as random effects models using weighted mean differences for continuous outcomes and relative risk for dichotomous outcomes with 9% confidence interval. Heterogeneity was to be investigated including both clinical and methodological factors. Main results No RCTs or controlled clinical trials (CCTs) were identified. 1

4 Authors conclusions There is an urgent need for RCTs in this area, since zygomatic implants, if found to be at least as effective as other augmentation procedures, may involve major advantages for both patients and society. S Y N O P S I S There is no strong evidence to compare the effectiveness of dental implants into the cheekbone as an alternative to bone grafting or similar procedures. Sometimes there is not enough bone in the upper jaw in which to secure dental implants. Bone is sometimes grafted from somewhere else in the person s body, involving a series of operations. People have to wait about a year before the implants can then be in use, and one out of four implants may fail. It is expensive and painful. An alternative is a long screw-shaped implant that is inserted into the cheekbone (zygomatic implant). This may mean that bone grafting is unnecessary and implants can be fitted sooner. However, the review found no trials comparing the outcomes of zygomatic implants with conventional bone grafting. B A C K G R O U N D Dental implants are now commonly used for replacing missing teeth in various clinical situations. Dental implants are surgically inserted in the jawbones. However, the possibility of placing dental implants is limited by the presence of adequate bone volume permitting their anchorage. In many clinical situations, in particular for edentulous patients with heavily resorbed jawbones and patients who underwent traumatic bone loss or resective surgery for oral cancer, there is insufficient bone to allow implant placement. Unfortunately, these people have more problems to adapt to conventional dentures, since dentures cannot be easily stabilized in the mouth due to lack of retention and therefore these people have serious difficulties in eating and speaking. In order to solve this problem several bone grafting procedures have been developed. In principle the missing bone is taken from a donor site (for example the iliac crest), transplanted where needed and then implants are placed. Sometimes, major bone grafting operations have to be undertaken under general anaesthesia requiring patients to be hospitalized for a few days. Some degree of morbidity related to the donor site must be expected and two to three surgical interventions may be needed before the implants can be functionally used. Often patients have to wait more than 1 year before a denture can be fixed to the implants and the total cost of the treatment is high. However, the major problem is that about % of the implants placed in grafted bone fail (Esposito 1998), so this procedure can end in total failure for some patients. More information about the effectiveness of bone grafting procedures can be found elsewhere (Coulthard 003). At the beginning of the 1990s a long screw-shaped implant was developed by Professor P-I Branemark as an alternative to bone grafting: the zygomatic implant (Stevenson 000). Zygomatic implants are inserted into the body of the zygomatic bone (cheekbone). Their main advantages are that bone grafting may not be needed and patients may be fitted with a fixed denture much sooner. It is believed that two zygomatic implants are not sufficient to hold a fixed denture so they need some extra conventional implants (at least two) in the anterior portion of the maxilla (Bedrossian 001). This could only be accomplished if there is sufficient bone in the anterior portion of the maxilla, otherwise bone grafting is still needed. An alternative is to place two zygomatic implants in each zygoma. In addition, the placement of zygomatic implants requires particularly experienced surgeons and is generally done under general anaesthesia. At the moment, Nobel Biocare AB (Sweden) is the only manufacturer to have developed a commercially available titanium zygomatic implant called ZY- GOMA IMPLANT. It would be beneficial to both patients and society to identify whether zygomatic implants offer a more effective and safe alternative to bone grafting. O B J E C T I V E S The null hypothesis of no difference for each harmful and beneficial effect between zygomatic implants without bone augmenting procedures in comparison with conventional dental implants in augmented bone for severely resorbed maxillae, will be tested against the alternative hypothesis of a difference. C R I T E R I A F O R C O N S I D E R I N G S T U D I E S F O R T H I S R E V I E W Types of studies Randomised controlled clinical trials with a parallel group design. Types of participants Patients who have a maxilla that cannot be rehabilitated with conventional dental implants due to lack of bone, including patients

5 subjected to cancer ablation surgery and irradiation therapy with a follow up of at least 1 year. Patients can be partially or totally edentulous. Types of intervention Zygomatic implants without bone grafts versus conventional dental implants with bone grafts or other procedures for bone augmentation such as guided bone regeneration (GBR). Types of outcome measures Prosthesis could not be placed or loss of prosthesis secondary to implant failure. Implant failures defined as mobile implants, removal of stable implants dictated by progressive marginal bone loss or infection and implant fractures. Side effects. Patient satisfaction. Cost effectiveness. S E A R C H S T R A T E G Y F O R I D E N T I F I C A T I O N O F S T U D I E S See: search strategy For the identification of studies included or considered for this review we developed detailed search strategies for each database to be searched. These were based on the search strategy developed for MEDLINE (OVID) but revised appropriately for each database. The search strategy combined a sensitive search strategy for randomised controlled clinical trials (RCTs) (as published in Appendix c in the Cochrane Reviewers Handbook). The search strategy used a combination of controlled vocabulary and free text terms based on the following: #1 randomised controlled trial.pt. # controlled clinical trial.pt. #3 randomized controlled trials.sh. #4 random allocation.sh. # double blind method.sh. # single blind method.sh. #7 latin square.ti,ab. #8 crossover.ti,ab. #9 (split adj (mouth or plot)).ti,ab. #10 or/1-9 #11 (ANIMAL not HUMAN).sh. #1 10 not 11 #13 clinical trial.pt. #14 exp clinical trials/ #1 (clin$ adj trial$).ti,ab. #1 ((singl$ or doubl$ or trebl$ or tripl$) adj (blind$ or mask$)).ti,ab. #17 placebos.sh. #18 placebo$.ti,ab. #19 random$.ti,ab. #0 research design.sh. #1 or/13-0 # 1 not 11 #3 not 1 #4 1 or # exp Dental Implants/ # exp Dental Implantation/ or dental implantation.mp. #7 exp Dental Prosthesis, Implant-Supported/ #8 ((osseointegrated adj implant$) and (dental or oral)).mp. [mp=title, abstract, registry number word, mesh subject heading] #9 dental implant$.mp. [mp=title, abstract, registry number word, mesh subject heading] #30 (implant$ adj dent$).mp. [mp=title, abstract, registry number word, mesh subject heading] #31 dental-implant$.mp. [mp=title, abstract, registry number word, mesh subject heading] #3 (((overdenture$ or crown$ or bridge$ or prosthesis or prostheses or restoration$) adj10 (Dental or oral)) and implant$).mp. [mp=title, abstract, registry number word, mesh subject heading] #33 implant supported dental prosthesis.mp. [mp=title, abstract, registry number word, mesh subject heading] #34 ( blade implant$ and (dental or oral)).mp. [mp=title, abstract, registry number word, mesh subject heading] #3 ((endosseous adj implant$) and (dental or oral)).mp. [mp=title, abstract, registry number word, mesh subject heading] #3 ((dental or oral) adj implant$).mp. [mp=title, abstract, registry number word, mesh subject heading] #37 ((zygoma$ OR malar$) adj implant$) #38 OR/-37 #39 4 AND 38 SEARCHED DATABASES The Cochrane Oral Health Group s Trials Register (to January 003) The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 00) MEDLINE (19 to February 003) EMBASE (1980 to February 003) The last electronic search was done on 7 February 003. The bibliographies of identified RCTs and review articles were to be checked for studies outside the handsearched journals. We independently searched PubMed using the related articles feature. LANGUAGE Non-English papers were to be included. UNPUBLISHED STUDIES Personal contacts were used to identify ongoing or unpublished RCTs. We wrote to more than oral implant manufacturers in an attempt to identify unpublished or ongoing studies and we specifically contacted the only known manufacturer. We asked for 3

6 unpublished and ongoing RCTs on an internet discussion group Authors of the identified RCTs were to be contacted. HANDSEARCHING Details of the journals being handsearched by the Oral Health Group s ongoing programme are given on the web site: The following journals were identified as being important to be handsearched for this review: British Journal of Oral and Maxillofacial Surgery, Clinical Implant Dentistry and Related Research, Clinical Oral Implants Research, Implant Dentistry, International Journal of Oral and Maxillofacial Implants, International Journal of Oral and Maxillofacial Surgery, International Journal of Periodontics and Restorative Dentistry, International Journal of Prosthodontics, Journal of the American Dental Association, Journal of Biomedical Materials Research, Journal of Clinical Periodontology, Journal of Dental Research, Journal of Oral Implantology, Journal of Oral and Maxillofacial Surgery, Journal of Periodontology, Journal of Prosthetic Dentistry. Where these had not already been searched as part of the Cochrane Journal Handsearching Programme, the journals were handsearched by one of the reviewers. M E T H O D S O F T H E R E V I E W The titles and abstracts (when available) of all reports identified by the search strategy were scanned independently by two reviewers. For studies appearing to meet the inclusion criteria, or for which there were insufficient data in the title and abstract to make a clear decision, the full report was obtained and assessed independently by two reviewers to establish whether the studies met the inclusion criteria or not. Disagreements were to be resolved by discussion. Where resolution was not possible, a third reviewer was to be consulted. All studies meeting the inclusion criteria were to undergo quality assessment and data were to be extracted. Studies rejected at this or subsequent stages were to be recorded in the table of excluded studies, and reasons for exclusion recorded. QUALITY ASSESSMENT The quality assessment of the included trials was to be undertaken independently and in duplicate by two reviewers based on what was written in the articles. Three main quality criteria were to be examined: 1) Randomisation and allocation concealment, recorded as: (A) Adequate (B) Unclear (C) Inadequate (D) Not used ) Independent assessor as: (A) Yes (B) No (C) Unclear 3) Completeness of follow up (is there a clear explanation for withdrawals and drop outs in each treatment group?) assessed as: (A) Yes (B) No. After taking into account the additional information provided by the authors of the trials, studies were to be grouped into the following categories: A. Low risk of bias (plausible bias unlikely to seriously alter the results) if all criteria were met. B. Moderate risk of bias (plausible bias that raises some doubt about the results) if one or more criteria were partly met. C. High risk of bias (plausible bias that seriously weakens confidence in the results) if one or more criteria were not met as described in the Cochrane Reviewers Handbook.7. DATA EXTRACTION Data were to be extracted by two reviewers independently using specially designed data extraction forms. Any disagreement was to be discussed and a third reviewer consulted where necessary. Authors were to be contacted for clarification or missing information. Data were to be excluded until further clarification was available if agreement could not be reached. For each trial the following data were to be recorded: Year of publication, country of origin, setting and source of study funding. Details of the participants including demographic characteristics and criteria for inclusion. Details on the type of intervention. Details of the outcomes reported, including method of assessment and time intervals. DATA SYNTHESIS For dichotomous outcomes, the estimate of effect of an intervention was to be expressed as relative risks together with 9% confidence intervals. For continuous outcomes, mean differences and 9% confidence intervals were to be used to summarise the data for each trial. Clinical heterogeneity was to be assessed by examining the types of participants, interventions and outcomes in each study with a planned subgroup analysis for various bone grafting techniques and for different groups of patients (patients with severely resorbed maxillae versus cancer patients subjected to irradiation therapy). Meta-analyses were to be conducted only with studies of similar comparisons reporting the same outcome measures. Relative risks were to be combined for dichotomous data, and weighted mean differences for continuous data, using a random effects model. The significance of any discrepancies in the estimates of the treatment effects from the different trials was to be assessed by means of Cochran s test for heterogeneity and any heterogeneity was to be investigated. Sensitivity analyses were to be undertaken to examine the effect of concealed randomisation and outcome assessor being independent 4

7 on the assessment of the overall estimates of effect. In addition, the effect of including unpublished literature on the review s findings was to be examined. D E S C R I P T I O N O F S T U D I E S No randomised controlled clinical trial was identified. A U T H O R S Implications for practice C O N C L U S I O N S Unfortunately no randomised controlled clinical trial (RCT) on this topic was identified so it is not possible to give any type of evidence-based advice to potential users with respect to the efficacy of zygomatic implants as an alternative to augmentation procedures for severely deficient maxillae. However, it seems that zygomatic implants yield high survival rates in poorly reported short term case-series investigations. M E T H O D O L O G I C A L - R E S U L T S - Q U A L I T Y Implications for research Even recognizing the fact that zygomatic implants are a relatively new treatment modality, it is disappointing that not even one abstract of a study, comparing zygomatic implants with alternative augmentation techniques, could be identified. It is therefore suggested that multicentre, well designed RCTs are urgently needed in this area. The potential advantages for the patients and society derived by the use of zygomatic implants as replacement of traditional bone grafting procedures would surely justify all the costs and the efforts to implement such trials. D I S C U S S I O N It is somewhat disappointing to find no randomised controlled clinical trials (RCTs) comparing zygomatic implants with bone augmentation techniques for the rehabilitation of the deficient maxilla. The largest trial published at the end of 00 on zygomatic implants consisted of a case series of five patients (Stevenson 000). We are also aware of a prospective, multicentre, long term, uncontrolled clinical trial sponsored by the manufacturer and of several case series reports published in abstract form (Nakai 001; Vrielinck 001; Malevez 00; Boyes-Varley 00), but these are not appropriate to answer our question. From such reports however, it seems that survival rates for zygomatic implants are high, ranging from 9% (Vrielinck 001) to 98% (Malevez 00). While the lack of long term clinical results can be explained by the fact that zygomatic implants are relatively new, it is really discouraging to observe that we were not able to identify even one ongoing comparative clinical trial testing the efficacy of zygomatic implants in comparison with traditional bone grafting procedures. This may be not totally surprising if one considers that in another Cochrane review on the efficacy of various bone augmentation procedures (Coulthard 003) only four RCTs were included and none reported clinical data of functionally loaded dental implants despite the large body of literature published in the last 0 years on this topic. Therefore, we foresee great opportunity for conducting high quality randomised controlled trials to investigate this important question. P O T E N T I A L I N T E R E S T C O N F L I C T O F Peter Thomsen has previously undertaken some research projects sponsored by Nobel Biocare, the manufacturer of Zygoma Implants but neither of these projects involved zygoma implants. A C K N O W L E D G E M E N T S We wish to thank Sylvia Bickley (Cochrane Oral Health Group) for her assistance with literature searching and Luisa Fernandez (Cochrane Oral Health Group) for her help with the preparation of this review and Nobel Biocare AB for providing valuable assistance for the identification of ongoing trials. We would also like to thank the following referees: Bertil Friberg, Jayne E Harrison, Lee Hooper, Ian Needleman and Goran Widmark. S O U R C E S O F S U P P O R T External sources of support Swedish Medical Research Council (949) SWEDEN Internal sources of support Sahlgrenska Academy at Goteborg University SWEDEN University Dental Hospital of Manchester UK

8 Additional references Bedrossian 001 Bedrossian E, Stumpel LJ III. Immediate stabilization at stage II of zygomatic implants: rationale and technique. Journal of Prosthetic Dentistry 001;8(1):10 4. Boyes-Varley 00 Boyes-Varley JG, Lownie JF, Howes DG, Blackbeard GA. Surgical modifications to the Branemark zygomaticus protocol. Clinical Oral Implants Research. 00;13(4):xxxii. Coulthard 003 Coulthard P, Esposito M, Worthington, Jokstad A. Interventions for replacing missing teeth: bone augmentation techniques for dental implant treatment (Cochrane Review). In: The Cochrane Library,, 003.Oxford: Update Software /14188.CD00307 Esposito 1998 Esposito M, Hirsch JM, Lekholm U, Thomsen P. Biological factors contributing to failures of osseointegrated oral implants. (I) Success criteria and epidemiology. European Journal of Oral Sciences 1998; 10:7 1. Malevez 00 Malevez C. Zygomatic implants. Clinical Oral Implants Research. 00;13(4):vi. Nakai 001 Nakai H, Okazaki Y, Ueda M. Clinical application of Zygomaticus implants for severely resorbed maxilla. Clinical Oral Implants Research. 001;1(4):410. Stevenson 000 Stevenson AR, Austin BW. Zygomatic fixtures - the Sydney experience. Annales of the Royal Australasian College of Dental Surgeons 000;1: Vrielinck 001 Vrielinck L. The use of a surgical drill guide for zygoma and pterygoid implants. Clinical Oral Implants Research. 001;1(4):40. R E F E R E N C E S This review has no graphs. G R A P H S A N D O T H E R T A B L E S I N D E X T E R M S Medical Subject Headings (MeSH) Alveolar Ridge Augmentation; Bone Transplantation; Dental Implantation, Endosseous; Dental Implants; Dental Prosthesis, Implant- Supported; Jaw, Edentulous [ rehabilitation] MeSH check words Humans Title C O V E R S H E E T Interventions for replacing missing teeth: dental implants in zygomatic bone for the rehabilitation of the severely deficient edentulous maxilla

9 Authors Contribution of author(s) Issue protocol first published 003/ Review first published 003/3 Date of most recent amendment November 003 Date of most recent SUBSTANTIVE amendment What s New Date new studies sought but none found Esposito M, Worthington HV, Thomsen P, Coulthard P Conceiving, designing and co-ordinating the review (Marco Esposito (ME)). Developing search strategies and undertaking searches (ME, Paul Coulthard (PC)). Screening search results and retrieved papers against inclusion criteria (ME, PC). Writing the review (ME). Providing general advice on the review (PC, Helen Worthington (HW), Peter Thomsen (PT)). 3 February 003 Date new studies found but not yet included/excluded Date new studies found and included/excluded Date authors conclusions section amended DOI Cochrane Library number Editorial group Editorial group code /14188.CD00411 CD00411 Cochrane Oral Health Group HM-ORAL 7