The orthopaedic effects of bone-anchored maxillary protraction in a beagle model

Abstract

The purpose of this study was to establish an animal model of bone-anchored maxillary protraction (BAMP) and verify the effects of such treatment in this model. Ten total immature (90-day-old) male beagle dogs were used. On Day -20, one miniplate per jaw quadrant was placed and secured with screws. From Day 0 to Day 60, miniplates in the dogs in the intermaxillary traction group (group T, n = 5) were loaded with coil springs. In the control group (group C, n = 5), the miniplates received no force. Every 20 days from Day -20, all dogs were assessed by measuring body weight, taking photographs, and acquiring standardized lateral cephalometric radiographs using a specially designed cephalostat. Cephalometric analyses were performed and the two groups compared. New bone formation was labelled by double-fluorochrome administration with calcein and tetracycline. Animals were sacrificed at Day 60, and bone sections of zygomaticomaxillary sutures were analysed using histomorphometry with fluorescence microscopy. Groups were compared with Mann-Whitney U-tests (P < 0.05). Cephalometric analysis indicated significant maxillary advancement and retroclination of maxillary incisors in group T, with concomitant significant posterior relocation of the condyles and proclination of the mandibular incisors. In histological analysis, vigorous bone apposition at the zygomaticomaxillary suture was only detected in group T. Further histological studies would clarify the effects of BAMP on the mandible, especially on temporomandibular articulation. Our results, using this newly developed animal model, support the orthopaedic effects of BAMP.