LAUSR

AIM To evaluate the impact of a collagen membrane on bone remodeling and osseointegration of implants placed simultaneously with a bone ring technique. MATERIAL AND METHODS Standardized, vertical alveolar bone defects in the mandibles of six dogs were created. Tapered dental implants designed for two-stage subcrestal placement were inserted simultaneously with a bone ring technique. On one side of the mandible, the augmented sites were covered with a collagenous membrane. Implants with (M Group) and without membranes (NM Group) were left for an osseointegration period of 3 and 6 months, respectively. Block biopsies of the implants with surrounding bone were harvested and analyzed histologically. RESULTS Implant exposure was a common finding (2/3) concomitantly with loss of healing caps. It appeared to be related to advanced bone loss around the implants. Exposure of implants was more frequent in M Group, however, without significant differences when compared to NM Group. The total bone area within the region of the bone ring was greater in the NM Group compared to the M Group. Moreover, in the region of the pristine bone of the M Group, the total bone was greater than at the corresponding NM Group sites at both observation periods. A nonparametric analysis of variance (ANOVA) revealed no significant effects of membrane placement or healing period on the total area of the bone. The total bone-to-implant contact (BIC) for the two groups was similar at each observation time point. However, BIC increased significantly at 6-month compared with 3-month observation period (p = .0088) in both groups. CONCLUSIONS In vertical bone augmentation applying the bone ring technique, the disruption of soft tissue was a frequent complication. Membrane placement yielded no significant advantage on the osseointegration (BIC) of implants or bone characteristics.