Evaluation of implants coated with rhBMP-2 using two different coating strategies: A critical-size supraalveolar peri-implant defect study in dogs

Background: Implants coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) induce relevant bone formation but also resident bone remodelling. Objectives: To compare the effect of implants fully or partially coated with rhBMP-2 on new bone formation and resident bone remodelling. Materials and Methods: Twelve, male, adult, Hound Labrador mongrel dogs were used. Critical-size, supraalveolar, peri-implant defects received titanium porous oxide surface implants coated in their most coronal aspect with rhBMP-2 (coronal-load/six animals) or by immersion of the entire implant in an rhBMP-2 solution (soak-load/six animals) for a total of 30 μg rhBMP-2/implant. All implants were air-dried. The animals were euthanized at 8 weeks for histometric evaluation. Results: Clinical healing was uneventful. Supraalveolar bone formation was not significantly affected by the rhBMP-2 application protocol. New bone height and area averaged (± SE) 3.4 ± 0.2 versus 3.5 ± 0.4 mm and 2.6 ± 0.4 versus 2.5 ± 0.7 mm² for coronal-load and soak-load implants, respectively (p>0.05). The corresponding bone density and bone-implant contact (BIC) recordings averaged 38.0 ± 3.8% versus 34.4 ± 5.6% and 25.0 ± 3.8% versus 31.2 ± 3.3% (p>0.05). In contrast, resident bone remodelling was significantly influenced by the rhBMP-2 application protocol. Bone density outside the implants threads averaged 74.7 ± 3.8% and 50.8 ± 4.1% for coronal-load and soak-load implants, respectively (p<0.05); bone density within the thread area averaged 51.8 ± 1.2% and 37.8 ± 2.9%, and BIC 70.1 ± 6.7% and 43.3 ± 3.9% (p<0.05). Conclusion: Local application of rhBMP-2 appears to be a viable technology to support local bone formation and osseointegration. Coronal-load implants obviate resident bone remodelling without compromising new bone formation.