Regeneration procedures in immediate transmucosal implants: An animal study

The aim of the present study was to evaluate bone regeneration around nonsu bmerged implants placed immediately in extraction sites in the canine mandi ble using a combination of synthetic hydroxyapatite (HA) and collagen membr anes. Ten beagle dogs were used in this study. After the second and third m andibular premolars were extracted, hollow-screw implants were placed in th e distal extraction sockets. In each animal, one sire received no treatment (control site), while other defects received randomly 1 of the following t reatments: grafting with porous HA in the peri-implant region, collagen mem brane adapted to the implant cervical collar covering the peri-implant defe cts, or a combination of the 2 treatments, ie, HA grafting and membrane pla cement. After 4 months of healing, block biopsies were obtained and prepare d for histologic analysis using the cutting-grinding technique. The histome tric evaluation took into account the number of integrated screw threads, t he extent of bone-to-implant contact, and the density of peri-implant bone. At sites covered by membrane alone or by membrane and HA, the number of in tegrated threads was statistically higher than sites treated only with HA. The extent of bone-to-implant contact was significantly different between t reatments. However, the use of bioabsorbable materials did not significantl y enhance peri-implant bone regeneration in immediate implantation.