[Preoperative cephalometric simulation in orthodontic surgery].

The authors expand their method of cephalometric simulation, which was designed for maxillofacial surgeons performing orthognathic surgery. This method has been developed to make up for the insufficiencies of the usually available cephalometric simulations, ie. poor legibility and the lack of data that may be necessary for surgery. The authors only deal with CS on profile teleradiographs at the end of the orthodontic preparation. This method utilizes models cut out of colored polyester and representing the profile of the maxillary and mandible. All the possible movements of the skeletal parts can also be simulated and the analysis of their direction and amplitude is possible, as is, more importantly, the influence of vertical movements of the maxillary on the mandible due to the mandibular autorotation phenomenon. This method is essential to accurately assess the degree of differential impaction or egress of the mandible in the region of the incisors and of the molars, according to the accompanying movements of the mandible moving around the condyle. Examples illustrate the use of this simulation method in the various types of orthognathic surgery. Finally, the authors point out the limitations of the method and the complementary usefulness of anteroposterior cephalometric simulation and of gnathologic simulation on casts, in particular for osteotomies for the transverse direction and for asymmetria.