Evaluation of a prototype trilayer membrane (PTLM) for lateral ridge augmentation: an experimental study in the canine mandible

The objective of this animal study was to evaluate a biodegradable/bioresorbable prototype trilayer membrane (PTLM) consisting of two collagen layers and an internal polylactide layer for lateral ridge augmentation in conjunction with two different bone grafting materials: particulate autograft or deproteinized bovine bone mineral (DBBM). In four mongrel dogs, two lateral bone defects per side were created in the mandible. The four defects per dog were randomly subjected to the following grafting treatments 3 months later: 1. PTLM+DBBM, 2. PTLM+particulate autograft, 3. ePTFE membrane+DBBM, 4. ePTFE membrane+particulate autograft. After a healing period of 4 1/2 months, the dogs were sacrificed for histological and histomorphometrical analysis. Percentage calculations for areas showing bone regeneration within the former defect outline were 56.8% for PTLM+DBBM, 85.2% for PTLM+autograft, 52.3% for ePTFE+DBBM, and 96.9% for ePTFE+autograft (differences between autograft and DBBM sites were significant at P<0.01 to P<0.05). Measurements of ridge enlargement (horizontal bone gain) were also significantly better for autograft+ePTFE sites compared to the other three grafting treatments. Histology demonstrated for most PTLM sites a moderate infiltration of lymphocytes and plasma cells adjacent to empty spaces corresponding to polylactide fragments. In addition, these reactions appeared to provoke subsequent resorption of newly formed bone. No such findings were seen in ePTFE sites. The tested prototype membrane cannot be recommended for clinical application.