Mandibular growth following Le Fort I osteotomy in adolescent monkeys.

Le Fort I osteotomy with anterior and superior repositioning of the maxilla was performed on adolescent Macaca fascicularis monkeys to study its effect on the subsequent growth and remodeling changes of the mandible. Six adolescent Macaca fascicularis monkeys were randomly divided into two surgical groups and eight others served as controls. Group I animals underwent a Le Fort I advancement and Group II animals experienced a Le Fort I advancement and impaction. All monkeys received tantalum implants in the anterior part of the cranial base, on opposite sides of craniofacial sutures and in multiple sites of the maxilla and mandible. The immediate postsurgical occlusion of all experimental animals was a Class II molar relationship. The animals were followed for up to 12 months postoperatively. Analysis of cephalometric head films taken at monthly intervals showed that both the maxilla and the mandible of all experimental monkeys grew in a coordinated fashion, although the amount, rate, and direction of growth varied between control and experimental animals as well as between Group I and Group II animals. The largest increments and rates of growth were observed in the control animals, Group I animals, and Group II animals, respectively. This study indicates that the growth changes in both maxilla and mandible are related to the extent of injury caused by maxillary surgery. The results also showed that although the surgical procedures were performed in the maxilla, mandibular growth was significantly modulated by the surgically changed maxillary environment.

Facial growth subsequent to Le Fort I osteotomies in adolescent monkeys.

The study goal was to assess qualitatively and quantitatively the craniofacial adaptations following total maxillary osteotomy with and without mandibular autorotation. Six adolescent female Macaca fascicularis monkeys were randomly divided into two surgical groups, and eight others served control. Prior to surgery, metallic implants were inserted in the anterior part of the cranial base, on opposite sides of craniofacial sutures, and in multiple sites of the maxilla and mandible. Group I animals underwent a Le Fort I advancement of 4 mm, while Group II animals had a 5-mm advancement and a 2.5-mm impaction. Lateral cephalometric head-films were taken at monthly intervals for a total follow-up of 12 months after surgery. At least two cephalograms were taken on each occasion, one with the teeth in occlusion and the other with the mouth wide open. The latter was used to ascertain accurately the outline of the mandibular condyle. Cephalometric superimposition methods were used to quantify the growth changes. The findings indicated that the growth changes in the maxilla and mandible were related to the extent of injury caused by maxillary surgery. The largest increments and rates of growth were observed respectively in the control animals, Group I animals (anterior maxillary repositioning), and Group II animals (anterior and superior maxillary repositioning). The most interesting finding was that mandibular growth pattern followed maxillary growth pattern in both experimental groups, and the immediate postsurgical occlusion in Class II molar relationship was maintained with increased overjet in both experimental groups throughout the postsurgical observation period.