Repair of surgical clefts of the hard palate in beagles

The biological responses to the repair of palatal clefts has been evaluated principally by monitoring craniofacial growth. Little is known about the regenerative ability of the repaired palate. In the present study, 18 Beagle pups (51 to 58 days old) were assigned to one of three groups: (1) control group, having no surgery; (2) cleft group, having a surgically created cleft of the posterior hard palate (mean bony measurement: 3.1 x 11.7 mm) at 8 weeks of age; and (3) repaired group, same as group 2, and followed by soft-tissue closure at 12 weeks of age. Craniofacial growth was monitored by cephalometric and dental cast measurements. Records were taken at 6-week intervals. Animals were sacrificed either 16 or 28 weeks after time of cleft creation. Routine histologic examination and histochemical detection of alkaline phosphatase activity were performed to examine the quality and extent of soft-tissue repair and bone formation. Analysis of the cleft palate group revealed that the size of the bony cleft increased with time. The histologic examination demonstrated at 24 weeks of age (12 weeks after the repair) active reduction of medial margin of the bony palate as evidenced by osteoclastic activity. At 36 weeks of age, neither osteoblastic nor osteoclastic activity was detected. The mean dimensions of the bony cleft, in the cleft group at 36 weeks, were 7.9 x 18.8 mm. In the repaired group, partial bone repair occurred. However, no consistency was seen in predicting extent or location of repair. Histochemical detection of alkaline phosphatase activity indicated that the repaired group had greater amounts of new bone formation. In some sites, suture regeneration was seen. As with the amount of bone formation, the amount of suture regeneration was variable. This study revealed that the presence of a cleft inhibits osteoblastic activity along the margin of the cleft, and there is limited potential for regeneration of the palate subsequent to the repair.