Osseointegration of Dental Implants Complexed with rhBMP-2: A Comparative Histomorphometric and Radiographic Evaluation
Nikitas Sykaras, DDS, PhD/ Ronald D. Woody, DDS/Anthony M. Iacopino, DMD, PhD/R. Gilbert Triplett, DDS, PhD/Martha E. Nunn, DDS, PhD
Purpose: To evaluate the effect of rhBMP-2 on implant osseointegration using histomorphometric and radiographic imaging analyses and determine the diagnostic accuracy of periapical radiographs regarding clinical bone-implant contact levels. Materials and Methods: Hollow-cylinder implants were filled with an absorbable collagen sponge soaked with recombinant human bone morphogenetic protein-2 (rhBMP-2) or left empty and implanted in the mandibles of dogs. Animals were followed for 2, 4, 8, or 12 weeks. At the end of each time interval, the animals were sacrificed and specimens were collected for histomorphometric and radiographic evaluation of the bone-implant contact levels. Results: Both groups exhibited the same mean histologic bone-implant contact on the outer surface of the implant, except for the 4-week group. The radiographic evaluation of bone-implant contact overestimated the actual osseointegration levels by at least 30%, a significant amount. Discussion: The osteoinductive and regenerative potential of rhBMP-2 is of clinical benefit in cases where bone augmentation is indicated and improved levels of osseointegration are expected. Radiographic evaluation has been the most widely employed technique in clinical practice for assessing bone levels around dental implants and comparing changes over time. However, there is a limit to the diagnostic accuracy of conventional radiographs when compared to the data obtained by histologic analysis. Conclusion: Application of rhBMP-2 within the confined boundaries of the hollow chamber of the implant had a limited effect on the osseointegration level along its outer surface, perhaps because of physically restricted diffusion. Radiographic evaluation resulted in the overestimation of bone-implant contact, and poor correlation with the histomorphometric data was found.