BONE-FORMATION AND REOSSEOINTEGRATION IN PERI-IMPLANTITIS DEFECTS FOLLOWING SURGICAL IMPLANTATION OF RHBMP-2

This study was designed to evaluate bone formation and reosseointegrat ion following surgical implantation of recombinant human bone morphoge netic protein-e (rhBMP-2) in peri-implantitis defects. Hydroxyapatite- coated dental implants were placed bilaterally in the mandibular and m axillary premolar area in four rhesus monkeys and were allowed to osse ointegrate for 1 year. Cotton ligatures were then placed around the he aling abutments, and plaque was allowed to accumulate for 11 months. R esulting circumferential peri-implantitis defects exhibited a large in trabony and horizontal component. At reconstructive surgery, peri-impl antitis defects in contralateral jaw quadrants were randomly assigned to receive rhBMP-2 (0.43 mg/mL implant volume) in an absorbable collag en sponge carrier or a carrier control. The animals were sacrificed 4 months postsurgery, and block sections were prepared for histometric a nalysis. Summary statistics included means calculated per animal. Pair ed t tests were used to evaluate differences between experimental cond itions (n = 4). Defect depth amounted to 3.4 +/- 0.9 mm and 3.2 +/- 0. 9 mm for rhBMP-2 and control defects, respectively. Vertical bone gain in rhBMP-2 defects (2.6 +/- 1.2 mm) was significantly greater than in controls (0.8 +/- 0.8 mm; P < .01). Reosseointegration within the con fines of the defect for rhBMP-2 defects (29.0 +/- 10.5%) differed sign ificantly from that in the control (3.5 +/- 2.5%; P < .01). Reosseoint egration within the extent of newly formed bone averaged 40.0 +/- 11.0 % in rhBMP-2 defects as compared to 8.9 +/- 7.8% in the control (P < . 01). Osseointegration in resident bone amounted to 69.5 +/- 6.9% and 7 2.6 +/- 8.0% for rhBMP-2 and control defects, respectively. There is s ignificant evidence that rhBMP-2 has potential to promote bone formati on and reosseointegration in advanced peri-implantitis defects in a de manding nonhuman primate model.