Surgically assisted rapid orthodontic lengthening of the maxilla in primates--a pilot study.

Orthodontic and surgical treatment of patients with maxillary retrusion and/or midface hypoplasia is challenging. This study was designed to show that the maxilla can be successfully lengthened by surgical assisted rapid orthopedic movement, using the principles of distraction osteogenesis. Three experimental and three control adolescent cynomolgus primates were used in this study. Metallic markers were placed in the cranial base and the maxilla and cephalometric x-ray films were taken. An orthodontic appliance was constructed with a Glen-Ross screw (Dentaurum, Newtown, Pa.) oriented anteroposteriorly. Anterior supraapical osteotomies of the maxilla were carried out. Bilateral horizontal and interdental osteotomies were created between the first premolars and the canine; the anterior six tooth dental-osseo segment was completely mobilized in all animals. Beginning 1 week after surgery, the orthodontic appliance was opened a quarter turn every 2 days until the anterior segment was advanced by 4 mm in two animals and 6 mm in one animal. Animals were killed at 6, 8, and 12 weeks after completion of the maxillary orthopedic advancement. Computerized tomographic scans of the maxillae were completed, and the specimens were then prepared by routine histologic methods for examination by light microscopy. The computerized tomographic scans showed bone deposition in the osteotomy sites, which was confirmed by histologic observations. Since this technique demonstrated repair by bone rather than soft connective tissue in the osteotomy sites, this procedure could be a useful method of treating midface retrusion.