Effect of recombinant human bone morphogenetic protein-2 on mandibular distraction at different rates in an experimental model

This study evaluates the effect of recombinant human (rh) bone morphogenetic protein (BMP)-2 on mandibular distraction at normal and rapid distraction rates. This study also determines the feasibility of compensating for the increased distraction rate by the addition of rhBMP-2 while maintaining the quality of the distraction regenerate. Twenty-four New Zealand white rabbits were divided into 2 groups, 1 treated at a normal distraction rate (0.9 mm/d) and the other at a rapid distraction rate (2.7 mm/d). At the end of the active distraction period, rhBMP-2 was injected into distraction regenerate, and the contralateral side was used as a control. The distraction regenerates were analyzed by plain radiography, microcomputed tomography, and mechanical testing. The results showed that rhBMP-2 can promote bone formation at both rapid and normal distraction rates. At week 2 and week 4 of consolidation, bone volumes in the BMP-injection sides were significantly higher than in the control sides, but no statistically significant difference was observed between the BMP-injection sides of the rapid and normal distraction groups. At week 8 of consolidation, mechanical testing demonstrated no significant difference of the failure load and stiffness between the BMP-injection and control sides. In conclusion, the study indicates that rhBMP-2 can enhance bone ossification at both normal and rapid distraction rates. The addition of rhBMP-2 can compensate for the rapid distraction rate in mandibular distraction osteogenesis. However, in the long term, the bone quality and stiffness of the distraction regeneration was not influenced by rhBMP-2.