ONE-STAGE HORIZONTAL GUIDED BONE REGENERATION WITH LAYERED AUTOLOGOUS BONE, ANORGANIC BOVINE BONE AND COLLAGEN MEMBRANES: SIX-YEAR RESULTS OF A PROSPECTIVE CASE-SERIES STUDY

PURPOSE. To present the results recorded six years after implant placement and simultaneous one-stage horizontal guided bone regeneration (GBR) using layers of autologous bone and anorganic bovine bone in association with resorbable collagen membranes. MATERIALS AND METHODS. This study was designed as an uncontrolled prospective case series. Partially edentulous patients having less than 6.0 mm and more than 4.0 mm of residual horizontal bone width were selected and consecutively treated with implant placement and simultaneous horizontal bone regeneration using autologous bone and anorganic bovine bone placed in layers and covered with a resorbable collagen membra-ne. Outcome measures were: implant and prosthesis failures, any complications, peri-im-plant marginal bone level changes, probing pocket depth (PPD), and bleeding on probing (BoP). RESULTS. In total, 45 consecutive patients (20 males and 25 females) of mean age 52.1 years each received at least one GBR procedure with contemporary placement of 63 implants. At follow-up examination 6 years after implant placement, six patients with seven implants dropped out. Of the remaining 39 patients (56 implants), no implant or prosthesis failed. In six patients (13.3%), the collagen membrane became slightly exposed one to two weeks after bone augmentation. Four of these patients were moderate smokers. Post-hoc analysis using Fisher’s exact test found a significant association (P = 0.0139) between smoking and early membrane exposure. No late complications occurred. Mean marginal bone level at implant placement was 0.12±0.14 (95% CI 0.08-0.17). A statistically significant amount of bone loss occurred between implant placement and six-year follow-up (difference 0.8±0.29 mm; 95% CI 0.71-0.88; P = 0.0000). The mean BoP value measured at definitive restoration delivery was 1.23±0.93 (IQR 0.4; 1.1; 1.8), while six years after implant placement it was 1.21±0.58 (IQR 0.8; 1.1; 1.6), but the difference was not statistically significant from baseline (0.02 0.79; 95% CI-0.32–0.36; P = 0.906). The mean PPD value measured at definitive restoration delivery was 2.62±0.59 mm (95% CI 2.45-2.79), while six years after implant placement it was 2.77±0.67 mm (95% CI 2.56-2.98). The difference from baseline was not statistically significant (0.15 0.63; 95% CI-0.12-0.42; P = 0.272). CONCLUSIONS. Within the limitations of the present study, one-stage horizontal guided bone regeneration with layered autologous bone, anorganic bovine bone and collagen membranes seems to be a viable option for the reconstructive treatment of horizontal bony defects at implant placement.