Effects of Class III magnetic orthopedic forces on the craniofacial sutures of rhesus monkeys

Introduction: The objectives of this study were to develop an intraoral intermaxillary Class III magnetic orthopedic appliance (MOA-III), to investigate the influence of Class III orthopedic forces on the craniofacial sutures of rhesus monkeys, and to elucidate the mechanism of Class III malocclusion orthopedic treatment. Methods: Six male rhesus monkeys in the mixed-dentition stage were divided into 3 groups of 2 each: a 90-day experimental group, a 45-day experimental group, and a control group. Six craniofacial sutures were observed. The experimental monkeys received heavy forces (300 g) per side initially, created by opposing Nd2Fe14B magnetic units in a cast MOA-III. The control groups received no treatment. Before the appliances were inserted, metal implants were placed in each animal as bone markers for direct measurement. To determine the rate of bone apposition, each animal was injected with fluorescent dyes intravenously before and during the experimental period. Intraoral photographs, dental casts, and cephalometric radiographs of each animal were obtained at the beginning and end of the experiment. Results: Distances between metal implants on both sides of the sutures were enlarged in the experimental groups. Cephalometric analysis showed that the treatment effects of MOA-III are a combination of skeletal and dental changes in the maxilla and the mandible. Distinct changes from physiologic growth remodeling were observed in some sutures but not in the control groups. No inflammation was noted in either experimental or control monkeys. Conclusions: The MOA-III can be an efficient intraoral appliance to treat Class III malocclusion that is caused by a deficient maxilla; heavy orthopedic forces (300 g per side) are safe and effective in the rhesus monkey.