Effect of absorbable membranes on sandwich bone augmentation

Objectives: This study was conducted to evaluate the effect of barrier membranes on sandwich bone augmentation (SBA) for the treatment of implant dehiscence defects. Materials and methods: Twenty-six implant-associated buccal dehiscence defects in 22 patients were treated according to the SBA concept - mineralized human cancellous allograft (inner layer), mineralized human cortical allograft (outer layer) and coverage with barrier membrane. The defects were randomly assigned to the bovine collagen membrane (BME) group; acellular dermal matrix (ADM) group; and no membrane group. Measurements at baseline and 6 months re-entry included defect height (DH: from smooth-rough junction to the most apical part of the defect), defect width (DW: at the widest part of the defect), and horizontal defect depth (HDD: at three locations - smooth-rough junction, middle, and most apical portion of the defect). All measurements were taken from a reference stent. Statistical analyses were performed for comparison of intra- and inter-group comparisons. Results: All implants placed were successfully osseointegrated. DH at baseline for three groups were not significantly different (P=0.858). Mean % DH reductions for ADM, BME, and control groups at 6 months were 73.9 +/- 17.6%, 68.1 +/- 30.1%, and 63.6 +/- 23.9%, respectively, with no significant difference among the groups (P=0.686). Mean horizontal bone gain, however, was significantly greater for membrane groups (1.7 mm for ADM, 1.6 mm for BME) compared with control group (1 mm) (P=0.044). Implant exposure resulted in significant reduction in total height gain (79.1 +/- 14.3% vs. 57 +/- 23.5%, P=0.021). Conclusions: Within the limit of this study, it is concluded that SBA technique achieved predictable clinical outcomes. The addition of absorbable membranes enhanced bone gain in thickness compared with membrane-treated sites.