Defects of the rat premaxilla as a model of alveolar clefts for testing bone-inductive agents.

Critical-sized defects were made in the premaxillary bone of Wistar male rats using a surgical trephine and a low-speed dental engine as a model of the maxillary alveolar cleft for testing bone-inductive agents. The defects were treated with either 7 mg of demineralized bone matrix (DBM) or were left nongrafted. The nongrafted group healed mainly with fibrous connective tissue, with a small amount of bone formation at the periphery. There was no significant change in alkaline phosphatase activity and 45Ca incorporation. The DBM-grafted group produced new bone with osseous bridging in the defect by day 35. Alkaline phosphatase activity increased significantly from day 10, reaching a maximum on day 14, and 45Ca incorporation increased on day 14. These results indicate that this nonhealing bony wound of the premaxilla in rats may be useful as a model for studying the effect of bone-inductive agents on the healing of alveolar clefts.