[Experimental study of secondary bone graft of alveolar clefts using bone morphogenetic protein (BMP)]

The purpose of this study was to evaluate the utility of recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone substitute on artificial alveolar clefts of adult Macaca fuscata monkeys. First, we created simulated alveolar clefts to represent human bilateral alveolar clefts, and then we implanted a mixture of rhBMP-2 and autogeneous particulate marrow cancellous bone (PMCB) into these models, as experimental groups. The mixture ratio was varied as follows (mixture ratio = rhBMP-2: PMCB). Group 1: rhBMP-2 alone. Group 2: Mixture of rhBMP-2 and PMCB (1:1). Group 3: Mixture of rhBMP-2 and PMCB (3:1). Group 4: Mixture of rhBMP-2 and PMCB (4:1). Positive control group: PMCB alone. Negative control group: PLGA (poly[L-lactide-co-glycolide] copolymer/gelatin sponge complex (PGS) alone. All animals were sacrificed 12 weeks after implantation and evaluated radiographically and histologically. The results were as follows. Bone bridge formation was not observed in Group 1, using rhBMP-2 alone, but it was observed in Groups 2, 3, and 4 using mixture of rhBMP-2 and PMCB. The vertical height of bone bridge formation in Group 4 was equal to that in the positive control group, roughly. The histological finding showed that the bone density of Group 4 was higher than in the positive control group, and the structure of cancellous bone turned into mature type. Bone formation and remodeling was active in Group 4. These results indicated that rhBMP-2 may be an effective substitute for autogenous PMCB in bone grafting into alveolar clefts.