A 7-year retrospective study of 423 immediate implants.

This article reports the results of a study conducted from 1989 to 1995 of 423 hydroxyapatite-coated implants used for immediate tooth replacement after extraction in 353 patients with an age range from 15 to 68 years. The implants replaced teeth that were extracted because of periodontal disease, root fractures, and endodontic problems. Bone defects relative to the implant were treated with bone regeneration procedures using polytetrafluoroethylene (PTFE) membranes and resorbable collagen membranes with and without augmentation material (hydroxyapatite--188 cases, demineralized freeze-dried bone allograft--208 cases, and 27 cases without augmentation material). Histologic evaluation confirmed viability of the regenerated bone. The length of implants ranged from 8 mm to 18 mm, and a total of 284 PTFE and 139 collagen membranes were used. During the 1-year follow-up, 1 implant was lost and an additional implant failed during the 7-year follow-up, with a final success rate of 99.53%.