Extraoral high-pull forces with rapid palatal expansion in the Macaca mulatta

Abstract

On the basis of the cephalometric and histologic findings, the following conclusions were made: Over-all evaluation of this study indicates that orthopedic forces brought about changes in sutural, endochondral, and appositional growth systems of the dentofacial complex. None of the changes produced was pathologic. Combining orthopedic forces and appliances in the form used in this study produces increased cellular activity in sutures while still maintaining cellular and sutural integrity. These forces decrease endochondral activity and apposition while maintaining cellular integrity. Squamous sutures are not as responsive to orthopedic forces as serrated sutures. Root resorption was a result of lateral and distal orthopedic movement. Discontinuation of orthopedic therapy allows resorption lacunae to return to normal by filling with cementum. The changes observed are a combination of slight tooth movement and much sutural adaptation. Observation of the procion dye indicates that the headgear traction decreases lateral apposition in facial bones. Occipital headgear traction force as applied in this study can alter the position of the maxilla. With proper management, the combination of the rapid palatal expansion appliances and the occipital-pull headgear may have implications in Class II, Division 1 and open-bite therapy. The exact mechanism of sutural movement found in this study is not understood. Superimposition of the zygomaticomaxillary implants indicates that sutural area and geometry of the face may be factors in determining changes resulting from orthopedic force. Orthopedic changes, like orthodontic changes, require retention. Specific attention to technique in fabrication of headgear for monkeys would aid in the study of orthopedic forces in animals. Future combination of orthopedic forces should be studied to determine the amount, duration, and application necessary to bring about desired skeletal changes.