- Email: [email protected]
Platform switching reduces peri-implant bone loss
RESEARCH
CRITICAL
SUMMARIES
Platform switching reduces peri-implant bone loss A critical summary of Atieh MA, Ibrahim HM, Atieh AH. Platform switching for marginal bone preservation around dental implants: a systematic review and meta-analysis. J Periodontol 2010;81(10):1350-1366. Gerard Byrne, BDSc, MSD
Systematic review conclusion. Some evidence exists to indicate that platform switching preserves peri-implant bone height. Critical summary assessment. Platform switching does not affect implant survival, but it does preserve proximal bone height and, thus, can be recommended cautiously. The authors of the review did not study soft-tissue (esthetic) outcomes. Evidence quality rating. Limited.
Clinical question. Does the use of smaller-diameter abutments (platform switching) compared with matched-diameter implant abutments (platform matching) improve the survival rate and maintain the marginal bone level around implants? Review methods. The authors searched eight Englishlanguage databases through February 2010 for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared platform-switched with platform-matched implant treatment groups. The selected studies (seven RCTs and three CCTs) met the minimum requirements of involving 10 implants and 12 months of follow-up. Some studies included immediate placement and early loading of implants. The primary outcome was radiographic marginal bone loss, and the secondary outcome was implant loss. The statistical unit was the implant, not the patient. The authors conducted the review and meta-
analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. They calculated mean differences (MDs) to analyze continuous data and used risk ratios (RRs) for dichotomous data with 95 percent confidence intervals (CIs). Main results. The authors included 10 studies with a total of 1,239 implants in their systematic review and meta-analysis. Followup ranged from 12 to 60 months. Marginal bone loss around platform-switched implants was significantly less than that around platform-matched implants (MD, −0.37 millimeters; 95 percent CI, −0.55 to −0.20; P < .0001). The difference was greater in studies lasting longer than 12 months. The results of a subgroup analysis for the five studies with sample sizes of 60 or more implants showed a borderline significant difference favoring platform switching (MD, −0.23; 95 percent CI, −0.47 to 0.00; P = .05) over platform matching.
For the studies with sample sizes of less than 60 implants, the authors found a significant difference that favored platform switching (MD, −0.50; 95 percent CI, −0.78 to −0.22; P = .0005) over platform matching. They found no significant differences between groups regarding implant survival (RR, 0.93; 95 percent CI, 0.34 to 2.95; P = .89); that is, a 7 percent risk of implant failure. The results of additional subgroup meta-analysis of study variants revealed further differences. The authors found significantly less bone loss in cases in which there was an implantabutment diameter difference of ≥ 0.4 mm (MD, −0.50 mm; 95 percent CI, −0.72 to −0.29; P < .0001). In addition, the placement of implants in healed sites compared with placement in extraction sites revealed a significant difference in favor of platform switching (MD, −0.50 mm; 95 percent CI, −0.54 to −0.17; P = .0001). Conclusions. Some evidence exists to indicate that platform switching preserves peri-implant bone height. Marginal bone loss is related inversely to the extent of the implant-abutment diameter mismatch. No sources of funding for this systematic review were listed.
Dr. Byrne is an associate professor, Department of Adult Restorative Dentistry, College of Dentistry, University of Nebraska Medical Center, Lincoln. He also is an evidence reviewer for the American Dental Association. Address reprint requests to Dr. Byrne at Department of Adult Restorative Dentistry, College of Dentistry, University of Nebraska Medical Center, 40th and Holdrege St., Room 2163, Lincoln, Neb. 68339, e-mail [email protected].
JADA 143(7)
http://jada.ada.org
Copyright © 2012 American Dental Association. All rights reserved.
July 2012 787
RESEARCH
CRITICAL
SUMMARIES
COMMENTARY
Importance and context. Peri-implant crestal bone level is a criterion for implant success. The bone supports the marginal and interdental gingiva, which has implications for esthetics. Traditionally, radiographic marginal bone loss of approximately 1.5 mm occurred during the first year after abutment connection at second-stage surgery. Lazzara and Porter1 reviewed the concept of platform switching and found that there was little bone loss around large-diameter implants when standard (smaller) -diameter abutments were connected. Broggini and colleagues2 and Enkling and colleagues3 suggested that the microbiota at the implant-abutment junction might be the cause of early bone loss. This problem can be avoided by moving the implant-abutment junction away from the bone crest. As a result, implant manufacturers have incorporated platform switching into their designs to reduce initial bone loss and enhance gingival contours and esthetics. Conversely, the mechanical advantage of using large-diameter implants may be somewhat negated by using smaller diameter abutments. Strengths and weaknesses of the systematic review. This is a sound systematic review that used accepted strategies to select and analyze studies. The authors stated that they applied their selection criteria rigorously, which led to there being only 10 studies for review. Study bias was not addressed adequately in that study samples were small and three CCTs were included. It also was not clear if implant manufacturers supported the studies. Publication bias was addressed adequately. The authors pointed out the main limitations of the studies, including the fact that the studies’ investigators measured only proximal bone levels and that initial bone crest position relative to implants was not standardized. The authors also commented on the importance of esthetic assessment. Radiographic bone level is a surrogate measurement for the esthetic outcome; the enhanced preservation of bone around a platform-switched implant may not necessarily improve esthetics. The authors did not discuss biomechanical aspects of platform switching. Suggestions were made for appropriate further studies in the area of platform switching.
788
JADA 143(7)
http://jada.ada.org
Strengths and weaknesses of the evidence. A significant number of studies (10) and implants (1,239) were included in the review. Seven RCTs and three CCTs were included. Study variations—including immediate and delayed placement, early and conventional loading and socket grafting—introduced greater heterogeneity to the data. There was risk of bias in all of the studies owing to inadequate allocation concealment; only one study was described as double masked. The duration of most studies was 24 months (range, 12 to 60 months). None of the investigators assessed esthetic outcome, which may be considered an advantage of platform switching, although the investigators in some studies did record gingival index scores. Implications for dental practice. Implant survival was not affected by platform switching. Limited short-term evidence indicated that platform switching preserves peri-implant bone height by a relatively small amount (0.37 mm) compared with platform matching. The longterm clinical significance of this difference is not clear. Opinions regarding the effect of platform switching on soft-tissue esthetics cannot be formulated without proper assessment. ■ Disclosure. Dr. Byrne did not report any disclosures. Critical Summaries is supported by grant G08 LM008956 from the National Library of Medicine and the National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Md. These summaries, published under the auspices of the American Dental Association Center for Evidence-Based Dentistry, are prepared by practitioners trained in critical appraisal of published systematic reviews who work under the mentorship of experts. The summaries are not intended to, and do not, express, imply or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. For more information on the evidence quality rating provided above and additional critical summaries, please visit http://ebd.ada.org. 1. Lazzara RJ, Porter SS. Platform switching: a new concept in implant dentistry for controlling postrestorative crestal bone levels. Int J Periodontics Restorative Dent 2006;26(1):9-17. 2. Broggini N, McManus LM, Hermann JS, et al. Peri-implant inflammation defined by the implant-abutment interface. J Dent Res 2006;85(5):473-478. 3. Enkling N, Boslau V, Klimberg T, et al. Platform switching: a randomized clinical trial—one-year results (abstract). J Dent Res 2009;88(special issue A):3394. http://iadr.confex.com/iadr/2009miami/ webprogram/Paper119183.html. Accessed May 29, 2012.
July 2012
Copyright © 2012 American Dental Association. All rights reserved.
CRITICAL
SUMMARIES
Platform switching reduces peri-implant bone loss A critical summary of Atieh MA, Ibrahim HM, Atieh AH. Platform switching for marginal bone preservation around dental implants: a systematic review and meta-analysis. J Periodontol 2010;81(10):1350-1366. Gerard Byrne, BDSc, MSD
Systematic review conclusion. Some evidence exists to indicate that platform switching preserves peri-implant bone height. Critical summary assessment. Platform switching does not affect implant survival, but it does preserve proximal bone height and, thus, can be recommended cautiously. The authors of the review did not study soft-tissue (esthetic) outcomes. Evidence quality rating. Limited.
Clinical question. Does the use of smaller-diameter abutments (platform switching) compared with matched-diameter implant abutments (platform matching) improve the survival rate and maintain the marginal bone level around implants? Review methods. The authors searched eight Englishlanguage databases through February 2010 for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared platform-switched with platform-matched implant treatment groups. The selected studies (seven RCTs and three CCTs) met the minimum requirements of involving 10 implants and 12 months of follow-up. Some studies included immediate placement and early loading of implants. The primary outcome was radiographic marginal bone loss, and the secondary outcome was implant loss. The statistical unit was the implant, not the patient. The authors conducted the review and meta-
analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. They calculated mean differences (MDs) to analyze continuous data and used risk ratios (RRs) for dichotomous data with 95 percent confidence intervals (CIs). Main results. The authors included 10 studies with a total of 1,239 implants in their systematic review and meta-analysis. Followup ranged from 12 to 60 months. Marginal bone loss around platform-switched implants was significantly less than that around platform-matched implants (MD, −0.37 millimeters; 95 percent CI, −0.55 to −0.20; P < .0001). The difference was greater in studies lasting longer than 12 months. The results of a subgroup analysis for the five studies with sample sizes of 60 or more implants showed a borderline significant difference favoring platform switching (MD, −0.23; 95 percent CI, −0.47 to 0.00; P = .05) over platform matching.
For the studies with sample sizes of less than 60 implants, the authors found a significant difference that favored platform switching (MD, −0.50; 95 percent CI, −0.78 to −0.22; P = .0005) over platform matching. They found no significant differences between groups regarding implant survival (RR, 0.93; 95 percent CI, 0.34 to 2.95; P = .89); that is, a 7 percent risk of implant failure. The results of additional subgroup meta-analysis of study variants revealed further differences. The authors found significantly less bone loss in cases in which there was an implantabutment diameter difference of ≥ 0.4 mm (MD, −0.50 mm; 95 percent CI, −0.72 to −0.29; P < .0001). In addition, the placement of implants in healed sites compared with placement in extraction sites revealed a significant difference in favor of platform switching (MD, −0.50 mm; 95 percent CI, −0.54 to −0.17; P = .0001). Conclusions. Some evidence exists to indicate that platform switching preserves peri-implant bone height. Marginal bone loss is related inversely to the extent of the implant-abutment diameter mismatch. No sources of funding for this systematic review were listed.
Dr. Byrne is an associate professor, Department of Adult Restorative Dentistry, College of Dentistry, University of Nebraska Medical Center, Lincoln. He also is an evidence reviewer for the American Dental Association. Address reprint requests to Dr. Byrne at Department of Adult Restorative Dentistry, College of Dentistry, University of Nebraska Medical Center, 40th and Holdrege St., Room 2163, Lincoln, Neb. 68339, e-mail [email protected].
JADA 143(7)
http://jada.ada.org
Copyright © 2012 American Dental Association. All rights reserved.
July 2012 787
RESEARCH
CRITICAL
SUMMARIES
COMMENTARY
Importance and context. Peri-implant crestal bone level is a criterion for implant success. The bone supports the marginal and interdental gingiva, which has implications for esthetics. Traditionally, radiographic marginal bone loss of approximately 1.5 mm occurred during the first year after abutment connection at second-stage surgery. Lazzara and Porter1 reviewed the concept of platform switching and found that there was little bone loss around large-diameter implants when standard (smaller) -diameter abutments were connected. Broggini and colleagues2 and Enkling and colleagues3 suggested that the microbiota at the implant-abutment junction might be the cause of early bone loss. This problem can be avoided by moving the implant-abutment junction away from the bone crest. As a result, implant manufacturers have incorporated platform switching into their designs to reduce initial bone loss and enhance gingival contours and esthetics. Conversely, the mechanical advantage of using large-diameter implants may be somewhat negated by using smaller diameter abutments. Strengths and weaknesses of the systematic review. This is a sound systematic review that used accepted strategies to select and analyze studies. The authors stated that they applied their selection criteria rigorously, which led to there being only 10 studies for review. Study bias was not addressed adequately in that study samples were small and three CCTs were included. It also was not clear if implant manufacturers supported the studies. Publication bias was addressed adequately. The authors pointed out the main limitations of the studies, including the fact that the studies’ investigators measured only proximal bone levels and that initial bone crest position relative to implants was not standardized. The authors also commented on the importance of esthetic assessment. Radiographic bone level is a surrogate measurement for the esthetic outcome; the enhanced preservation of bone around a platform-switched implant may not necessarily improve esthetics. The authors did not discuss biomechanical aspects of platform switching. Suggestions were made for appropriate further studies in the area of platform switching.
788
JADA 143(7)
http://jada.ada.org
Strengths and weaknesses of the evidence. A significant number of studies (10) and implants (1,239) were included in the review. Seven RCTs and three CCTs were included. Study variations—including immediate and delayed placement, early and conventional loading and socket grafting—introduced greater heterogeneity to the data. There was risk of bias in all of the studies owing to inadequate allocation concealment; only one study was described as double masked. The duration of most studies was 24 months (range, 12 to 60 months). None of the investigators assessed esthetic outcome, which may be considered an advantage of platform switching, although the investigators in some studies did record gingival index scores. Implications for dental practice. Implant survival was not affected by platform switching. Limited short-term evidence indicated that platform switching preserves peri-implant bone height by a relatively small amount (0.37 mm) compared with platform matching. The longterm clinical significance of this difference is not clear. Opinions regarding the effect of platform switching on soft-tissue esthetics cannot be formulated without proper assessment. ■ Disclosure. Dr. Byrne did not report any disclosures. Critical Summaries is supported by grant G08 LM008956 from the National Library of Medicine and the National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Md. These summaries, published under the auspices of the American Dental Association Center for Evidence-Based Dentistry, are prepared by practitioners trained in critical appraisal of published systematic reviews who work under the mentorship of experts. The summaries are not intended to, and do not, express, imply or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. For more information on the evidence quality rating provided above and additional critical summaries, please visit http://ebd.ada.org. 1. Lazzara RJ, Porter SS. Platform switching: a new concept in implant dentistry for controlling postrestorative crestal bone levels. Int J Periodontics Restorative Dent 2006;26(1):9-17. 2. Broggini N, McManus LM, Hermann JS, et al. Peri-implant inflammation defined by the implant-abutment interface. J Dent Res 2006;85(5):473-478. 3. Enkling N, Boslau V, Klimberg T, et al. Platform switching: a randomized clinical trial—one-year results (abstract). J Dent Res 2009;88(special issue A):3394. http://iadr.confex.com/iadr/2009miami/ webprogram/Paper119183.html. Accessed May 29, 2012.
July 2012
Copyright © 2012 American Dental Association. All rights reserved.