As part of an ongoing prospective study, the treatment of peri-implantitis defects using autogenous bone grafts was evaluated. This present report is based on data from 25 ITI screw implants in 17 patients with progressive peri-implant tissue destruction during the maintenance phase. Treatment of these lesions included raising flaps, removal of the surrounding granulation tissue, and air-polishing of the implant surface. Subsequently, corticocancellous bone grafts or particulate bone were placed into the peri-implant osseous defects, and the flaps were sutured around the cervical segment of the implants, allowing for transmucosal healing. Two of the 25 cases resulted in a negative outcome of the procedure. One of the transplants had to be removed 40 days after augmentation because of flap dehiscence and graft mobility. In another patient, the healing period was uneventful until the re-entry surgery, but when the site was reopened, the total graft volume was resorbed. The primary therapeutic success at re-entry surgery evaluated by intraoperative measurements resulted in a median defect depth reduction of 6.9 to 0.7 mm (P = .001), corresponding to a bone repair of 90%. The change in defect width was 1.9 mm (P = .002, repair 100%). A positive result of the reconstructive therapy has been observed during a re-evaluation time of up to 3 years. Median marginal bone loss was reduced from 6.2 to 2.3 mm after 2 and 3 years, respectively. The median vertical bone resorption of 4.5 mm was completely repaired. The crevicular fluid volume, a parameter of the level of marginal inflammation, along with probing depths and attachment levels, were reduced to a physiologic rate. The implant observation period until the first appearance of the lesion seems to be crucial to the effectiveness of the therapy. Early failures appearing within the first 2 years after implant placement showed a more stable therapeutic result over time. Keywords: autogenous bone grafts, dental implants/complications, DNA probe, implant failure, ITI screw implant, peri-implantitis