Retrospective Analysis of Bar-Retained Dentures with Cantilever Extension: Marginal Bone Level Changes Around Dental Implants over Time

Purpose: The aim of this study was to retrospectively determine whether a relationship exists between the length of the distal bar extension and the amount of marginal bone loss around implants supporting cantilevered bar-retained dentures. Materials and Methods: This study was performed using data from patients who had been restored with implant-supported cantilevered bar-retained prostheses. Panoramic radiographs were obtained annually starting at the time of prosthetic loading of the implants; the protocol included a 4-year observation period. Vertical changes in the bone level were measured on the mesial and distal of implant sites with respect to a defined reference point per implant system, and radiographic distortions were compensated. Statistical analysis was performed with the Wilcoxon signed-rank test, the Spearman rank correlation test, and the two-factor nonparametric analysis for repeated measurements. Results: A total of 48 edentulous patients who were consecutively treated with 313 dental implants and rehabilitated with 66 bar-retained prostheses were included in the study. Implants were used to support 30 prostheses in the maxilla (172 implants) and 36 prostheses in the mandible (141 implants). These prostheses were supported by bars with distal cantilevers of up to 12 mm. Patients with bars without cantilevers served as the control group. After 4 years, mean mesial bone loss was 2.20 ± 0.91 mm; for distal implant sites it was 2.31 ± 1.05 mm. The number of implants inserted and implant length did not correlate with bone loss. Jaw (maxilla versus mandible) and implant system exerted a significant influence on the amount of bone lost within the first year. Cantilever length did not influence marginal bone loss. Conclusion: In this clinical study, no influence of the length of cantilever extensions on crestal bone loss was found. Within the limitations of the study, the results indicate that restorations with distal bar extensions up to 12 mm are an adequate treatment option for edentulous patients. Keywords: biologic width, cantilever length, crestal bone loss, dental implants, implant-retained overdenture