Alterations in the upper facial growth of Macaca mulatta resulting from high-pull headgear.

Four prepubertal Macaca mulatta monkeys, ranging in age from 13 to 24 months, were used in an investigation of the effects of high-pull headgear (to a face-bow) therapy on the growth of the upper facial skeleton. Amalgam bone implants were placed across the frontomaxillary, frontozygomatic, zygomaticomaxillary, and zygomaticotemporal sutures in each animal. Three of the monkeys wore appliances consisting of a maxillary dental spling, a face-bow, two coil springs, and an acrylic helmet. The fourth monkey (control) wore only a dental splint and a face-bow. A continuous high-pull headgear force of 300 grams per side was applied to the three monkeys for 81, 87 and 89 days, respectively, before death. Procion brilliant red 8-HBS vital stain was administered to all four animals at the start of and 3 days before the end of the treatment period. The facial growth patterns were determined from lateral cephalograms taken before and after treatment, from direct measurement of implant separation at the sutures, and from histologic sections of the four mentioned facial sutures.