Maxillary alveolar cleft repair in dogs using recombinant human bone morphogenetic protein-2 and a polymer carrier

Recombinant human bone morphogenetic protein-2 was evaluated in maxillary alveolar clefts in 24 adult, skeletally mature Foxhound dogs. Bilateral clefts were prepared, 1 cm in bony width, lined with healthy epithelium, with functional teeth on each side, and were expected not to heal spontaneously with new bone. Preparation of bilateral clefts in 24 dogs permitted 48 recipient sites divided evenly among four treatments and two time periods (2 and 4 months), yielding six replicates per treatment per time. The overall goal for the study was to regenerate bone in the cleft using one of three treatments: (1) 200 mu g recombinant human bone morphogenetic protein-2 combined with the copolymer poly(lactide-co-glycolide) and autogenous blood, (2) poly(lactide-co-glycolide) and autogenous blood, or (3) an autograft from the posterior iliac crest. A fourth group consisted of untreated alveolar cleft defects. At designated times, dogs were euthanized, and the recipient beds with contiguous bone were recovered, processed, and assessed radiographically and histologically. Autograft-treated defects had more bone than other treatments at 2 months; however, by 4 months, there were no differences among treatments, except for the poly(lactide-co-glycolide) group, which had the least amount of bone. Response to the recombinant human bone morphogenetic protein-2 may have been suboptimal either because the dose was too low or because the poly(lactide-co-glycolide)-autogenous blood delivery system did not temporally maintain and spatially position recombinant human bone morphogenetic protein-2 at the recipient bed. In addition, the development of a nonhealing, critical-sized defect in the maxilla of the dog appears to require a more aggressive resection of bone to preclude spontaneous osseous regeneration.