The purpose of the present study was to examine the effect of treating bony craters around titanium dental implant with polytetrafluoroethylene membranes (PTFE), with and without grafting of hydroxyapatite (HA), and with HA alone. 4 standardized bone defects were prepared in the alveolar ridge of edentulous areas in each of 7 monkeys. A titanium implant was then placed centrally in each defect, and in each monkey, the defects were treated with 1 of the following 4 treatment modalities: (1) coverage with PTFE membrane; (2) grafting of HA and covering with a PTFE membrane; (3) HA grafting; (4) no treatment. Following a healing period of 12 weeks, all animals were sacrificed and mesio-distal ground sections of the treated areas were prepared. The histological analysis showed that all bone defects around the implants treated with PTFE membranes and 5 of the defects treated with HA and PTFE membranes were completely filled with new bone. The defects treated with HA alone and thecontrol defects with no treatment only demonstrated new bone formation in the bottom of the defects. The results suggest that bone defects around titanium implants can be treated wuccessfully with PTFE membranes.