Recombinant human bone morphogenetic: Protein-2 stimulation of bone formation around endosseous dental implants

Background: Successful endosseous implant placement requires that the impla nt be stable in alveolar bone. In certain cases, the implant can be stabili zed in native bone but some part of the implant is not covered by bone tiss ue. This often occurs during placement of implants into extraction sites or in areas where bone resorption has occurred and the ridge width is not suf ficient to completely surround the implant. In those cases, the clinician u sually employs a procedure to encourage bone formation. These procedures ty pically include a bone graft and/or membrane therapy. Recent advances have led to the isolation, cloning, and production of recombinant human proteins that stimulate bone formation. One of these bone morphogenetic proteins (r hBMP-2) has been extensively studied in animal models and is currently bein g tested in human clinical trials. Methods: In this study, rhBMP-2 was tested using a collagen sponge carrier to stimulate bone formation in defects in the canine mandible around endoss eous dental implants. Six animals had a total of 48 implants placed. rhBMP- 2 with the collagen carrier was implanted around 24 of these, the remainder having only the collagen carrier placed. Half the sites were covered with a nonresorbable expanded poIytetrafluoroethylene membrane. Histologic analy sis was performed after 4 and 12 weeks. The area of new bone formed, percen tage of bone-to-implant contact in the defect area, and percentage fill of the defect was calculated. Results: The addition of rhBMP-2 resulted in significantly greater amounts of new bone area and percentage of bone-to-implant contact and with more pe rcentage fill after 4 and 12 weeks of healing. The area of new bone formed was reduced after 4 weeks when a membrane was present but after 12 weeks, t here was no significant difference between membrane and non-membrane treate d sites. In some specimens, new bone was found coronal to the membranes, wi th rhBMP-2 - treated sites having greater amounts than non-rhBMP-2 - treate d sites. Conclusions: These data demonstrate that a bone differentiation factor sign ificantly stimulates bone formation in peri-implant bone defects in the can ine mandible. In addition, bone-to-implant contact was significantly enhanc ed along the rough implant surface. Membrane-treated sites had less new bon e formation after 4 weeks of healing but were similar to non-membrane sites after 12 weeks. These results demonstrate that rhBMP-2 can be used to stim ulate bone growth both around and onto the surface of endosseous dental imp lants placed in sites with extended peri-implant osseous defects.