Immediate postextraction implants: a histologic and histometric analysis in monkeys.

The aim of this study was to evaluate the reaction of peri-implant tissues to immediately placed titanium plasma-sprayed implants into extraction sockets. Six macaca fascicularis monkeys were used in the study. A total of 36 titanium plasma-sprayed implants (PHI, Legnano, Italy) were inserted in both arches (18 in the posterior maxilla and 18 in the posterior mandible). The two premolars and the first molars of the maxilla and the mandible of all animals were extracted, and immediate postextraction implants were placed. After a releasing periosteal incision, the flap was coronally repositioned and sutured. No barrier membranes were used, and the only graft material used was autogenous bone chips. The implants were loaded after 2 months. Six months after implant loading, a block section was carried out, the remaining defects were filled with nonresorbable hydroxyapatite, and all 36 implants were retrieved. The implants were treated with the Precise System (Assing, Rome, Italy), to obtain thin ground sections. A total of three slides were cut for each implant and were examined under normal and polarized light. A histomorphometrical analysis was done. All implants were covered by compact, mature bone under examination in light microscopy. A very high bone-implant contact percentage (65-70%) was observed. No bone loss was present after the loading period. These results indicate that implants placed into fresh extraction sites grafted with autogenous bone chips will heal in a predictable way.