The purpose of this study was to evaluate the use of a biodegradable membrane of polyhydroxybutyrate-hydroxyvalerate copolymer reinforced with polyglactin 910 fibers, as an occlusive barrier over implants placed into fresh extraction sockets. Ten dogs had the 3rd and 4th mandibular premolars extracted bilaterally. Each dog had 4 Astra Dental Implants placed directly into the fresh extraction sockets. The top of the fixtures was placed at the same level as the top of the buccal cortical bone. The two implants in the right side were covered with the hydrolyzable polyester material (polyhydroxybutyrate-hydroxyvalerate reinforced with polyglactin 910 fibers; PHB-HV/PG), and the 2 implants in the left side were controls without occlusive membranes. Soft tissue dehiscences were registered for half of the implants in the test side but were not noted in the control side. The histomorphological measurements after 12 weeks showed that the mean distance from the top of the fixtures to the first bone-to-implant contact was significantly greater than for the control side. The membrane-covered implants without dehiscences showed also significantly less bone fill compared with the control side. Inflammatory cell infiltrates were seen adjacent to all PHB-HV/PG membranes, and frequently the membrane material was surrounded by a fibrous tissue capsule. The polyester membranes used in this study interfered with the marginal bone healing adjacent to the immediately placed implants. An increased inflammatory reaction and significantly less marginal bone healing was registered in the membrane side compared with the control side.