Effect of recombinant human bone morphogenetic protein-2 on bone regeneration and osseointegration of dental implants

Recombinant human bone morphogenetic protein-2 (rhBMP-2) induced bone regen eration and osseointegration was evaluated in bony defects created within t he hollow chamber of endosseous dental implants in 14 foxhound dogs. Bilate ral extractions of mandibular premolars were performed and surgical implant ation of 104 hollow cylinder implants followed after 8 weeks of healing. Ex perimental implants had their hollow chamber filled with 20 mug of rhBMP-2 delivered with a bovine collagen carrier, whereas the control implants had their apical chamber left empty. Dogs were followed for 2, 4, 8 and 12 week s. Histomorphometric evaluation and immunohistochemical analysis were perfo rmed. Minimal bone was regenerated at 2 weeks for both groups. At 4 weeks, bone fill averaged 23.48% for the rhBMP-2 and 5.98% for the control group ( P <0.05). At 8 weeks, mean bone fill was 20.94% and 7.75% for the rhBMP-2 a nd the controls, respectively (P <0.05). At 12 weeks, mean bone fill was 31 .39% and 24.31% for the rhBMP-2 and control implants, respectively (P>0.05) . Bone-implant contact (BIC) increased for both groups over time and at 8 w eeks the rhBMP-2 BIC value was 18.65% and for the control 7.22% (P<0.05). A t 12 weeks, the BIC was 43.78% and 21.05% for the rhBMP-2 and the control g roup, respectively (P<0.05). Immunohistochemical staining for type II colla gen was positive only for parts of the collagen carrier and formation of ca rtilaginous intermediate was not observed in any of the specimens. The resu lts suggest that, in confined defects adjacent to dental implants, rhBMP-2 can induce bone regeneration in close apposition to the implant surface.