BONE-FORMATION AND OSSEOINTEGRATION STIMULATED BY RHBMP-2 FOLLOWING SUBANTRAL AUGMENTATION PROCEDURES IN NONHUMAN-PRIMATES

The purpose of this study was to evaluate bone formation and osseointe gration using titanium dental implants in the subantral space followin g surgical implantation of recombinant human bone morphogenetic protei n-2 (rhBMP-2). In each of four cynomolgus monkeys, one subantral site was treated with rhBMP-2 (0.19 mg per implant) in an absorbable collag en sponge (ACS). The contralateral site was treated with vehicle in AC S (control). Three months later, two screw-type titanium dental implan ts were placed into each augmented sinus, and one additional implant w as placed immediately anterior to the sinus. Thus, each animal had thr ee experimental sites: rhBMP-2, control, and nonsinus. Animals were sa crificed after an additional 3 months, and block sections were harvest ed and prepared for histometric analysis. Analysis of variance and t t ests were used to evaluate differences between experimental conditions . Mean (t SD) vertical bone gain was significantly greater in rhBMP-2 than in control sites (6.0 +/- 0.3 versus 2.6 +/- 0.3 mm; P < .002). B one density in rhBMP-2 sites averaged 14.4 +/- 2.9% versus 13.9 +/- 4. 6% and 14.1 +/- 3.6% for control and nonsinus sites, respectively, wit hout significant differences between experimental conditions. Bone-imp lant contact in rhBMP-2 sites (41.1 +/- 7.7%) was not significantly di fferent from that in control (38.9 +/- 12.4%) and nonsinus sites (46.8 +/- 10.6%). The present study provides evidence for considerable vert ical bone gain in the subantral space following surgical implantation of rhBMP-2, thus allowing placement of dental implants. The newly form ed bone appears to be of similar quality and to be as suitable for oss eointegration as the residual bone in this nonhuman primate model. Thu s, surgical implantation of rhBMP-2 appears to have clinical utility a nd may provide a realistic alternative to autogenous bone grafts for s ubantral augmentation procedures.