The aim of the present study was to experimentally induce peri implant bone defects around three different types of implants by plaque accumulation and to determine whether new bone formation can occur on previously contaminated dental implants. Dental implants were placed into the mandibles of beagle dogs. Gross plaque accumulation around the implants was undisturbed for 3 months, which resulted in circumferential peri-implant bone defects. Bony defects surrounding the hydroxyapatite implants were significantly greater than those around the titanium implants. Surgical treatment consisted of granulation tissue removal, preparation of the implant surface, and the placement of an e-PTFE membrane over each test implant. Before the flap was closed to cover the implants, perforations were made into the cancellous bone. Each control implant received identical treatment, but without placement of a membrane. Surgical exposure after an uneventful submerged healing period showed evidence of closure of the peri-implant bone defects. Corresponding histologic examination of 2-month sections demonstrated large amounts of rapidly formed lamellar bone beneath the membrane. Some areas of the previously contaminated implant surface showed evidence of e-osseointegration. These preliminary results support the hypothesis that plaque-induced peri-implant bone defects can be successfully treated by a submerged membrane technique in the dog model. Schlagwörter: bone regeneration, dental implants, experimental breakdown, e-osseointegration, surface preparation