3-year survival estimates of short (less than or equal to 6 mm) length implants and the relationship to crown-to-implant ratios.

Abstract

INTRODUCTION: The literature regarding survival of short implants is conflicting. Furthermore, excessive crown-to-implant ratios have been cited in the literature as being detrimental to implant survival. Hence, the purpose of this study was to determine the 3- year survival estimates, and the relationship between crown-to-implant ratios and survival of short, roughened, plateau-design implants. Additionally, risk factors for failure were evaluated. MATERIAL AND METHOD: This retrospective cohort study involved 341 patients who possessed at least 1 single ≤6mm length plateau-design implant supported restoration that had been surgically placed between August 2000 and June 2007. An electronic chart review was conducted to acquire data on patient demographics, implant location, bone density, length of time in function and/or implant failure, as well as the most recent digital periapical radiographs in which the entire crown and implant were visible. Data analysis was conducted utilizing appropriate univariate and multivariate regression statistics, as well as non-parametric Kaplan-Meier survival analysis in order to determine the overall 3-year survival rate. RESULTS: Data from 573 single implant-supported fixed restorations were tabulated and included in the study. 13 implants failed overall. The 3-year Kaplan-Meier survival analysis adjusted for clustered observations was found to be 93.9%. The average (SD) crown-to-implant ratio of implants that were in function was 2.06 (0.4), and the average (SD) crown-to-implant ratio of those that failed was 2.02 (0.3). This difference was not statistically significant. Results from the multivariate model found quality of bone, and history of adjacent endodontically treated teeth to be statistically associated with implant failure, with hazard ratios of 13.2 and 2.7 respectively (P ≤ 0.05). CONCLUSIONS:The results of this study suggest that the survival of short, roughened, plateau-design dental implants is comparable to implants of traditional lengths, which suggests that these implants are a clinically acceptable option where alveolar bone height is limited or anatomic limitations exist.