This study evaluates a prototype bioabsorbable physical barrier material for guided bone regeneration. Nonspacemaking dehiscence-type defects were surgically created in the right and left mandibles of six adult dogs. Each animal received six root-form threaded titanium implants. The osseous defects wre randomized to receive treatm ent by either the prototype bioabsorbable barrier composed of a copolymer of lactide and glycolide, an expanded polytetrafluoroethylene nonresorbable barrier, or no barrier (control). Clinical and histologic results after 3.5 months of wound healing indicated that exposed threads were covered when treated with the expanded polytetrafluoroethylene barrier. Minimal thread coverage was evident with the bioabsorbable barrier and the control.