Surgically assisted-rapid orthopedic lengthening of the maxilla in primates--relapse following distraction...

A recent study has shown that the maxilla in primates can be successfully lengthened (0.5 mm every other day up to 6.0 mm) by means of surgically assisted-rapid orthopedic movement, using the principles of distraction osteogenesis. The present study was designed to determine if the maxilla can be advanced at a faster rate and if relapse would occur after removal of the orthodontic appliance. Metallic markers were placed in the cranial base and maxilla of two Cynomolgus primates, and cephalometric radiographs were taken. Bilateral horizontal and interdental osteotomies were created between in the first premolars and the canines, and the anterior segment was completely mobilized. An orthodontic appliance was bonded to the teeth and the screw was closed, compressing the osteotomy site. One week postoperatively the appliance was opened four quarter turns every day until the anterior segment was advanced by 10 mm. Cephalometric radiographs were taken at 6, 8, and 12 weeks postadvancement. At 12 weeks, the orthodontic appliance was removed, and at that time and 2, 4, and 6 weeks later, cephalometric radiographs were taken and study models fabricated. At the end of the postretention period, the animals were sacrificed, and the maxillae were evaluated by light microscopy. Results showed that the maxilla can be successfully advanced at a faster rate and for longer distances, and that the advanced maxilla does not relapse during the 6-week postretention period.