Use of a bite-opening appliance in the miniature pig: modification of craniofacial growth.

The purpose of this study was to determine the growth response of pigs to a bite block, preparatory to investigating the functional correlates of altered growth. Three miniature pigs (Sus scrofa) wore bite-opening appliances, creating an anterior opening of 18-20 mm, for 42-67 days. Three untreated pigs served as controls. All animals received tantalum implants and tetracycline injections to track growth of the facial bones and sutures. Treatment caused relative intrusion of maxillary and mandibular posterior teeth, and supereruption and retroclination of anterior teeth. Vertical displacement of the premaxilla and maxilla of the experimental animals was altered significantly in the superior direction, as expected from previous studies on monkeys. Changes in condylar morphology were also found, and the jaw joint discs were remodeled. Contrary to primate findings, however, anterior growth of the premaxillary, maxillary and zygomatic bones was greatly reduced. This difference in response between monkeys and pigs may be due to the way the bite block altered the load on the zygomatico-maxillary suture.