術前矯正治療にオトガイ形成術と下顎前歯部歯槽骨切り術を併用した下顎後退症の１例

Abstract

It is not always simple to treat maxillary protrusion cases with marked labially inclined mandibular incisors and mandibular retrognathia. Optimal front teeth inclination, along with a proper maxillo-mandibular relation is a key factor in obtaining postsurgical longterm stability. When treating such cases, mandibular advancement only by sagittal ramus osteotomy does not lead to pertinent incisor angle at all, and hence it is crucial to improve incisor angle by other means. On such occasions, especially in narrow mandibular symphysis, the root exposes from the surface of the alveolar bone following axial improvements by ordinary orthodontic treatment. Meanwhile, anterior subapical alveolar osteotomy results in no bone contact to the basal stump of the segment, leading to poor alveolar segment stability. Therefore, we considered various treatment modalities of such condition, and finally used the following strategy. Namely, we performed genioplasty in the early stage of the presurgical orthodontic treatment to lay the infrastructure for the subsequent forward root movement. Following bone union at the osteotomy site, we secondarily carried out mandibular anterior subapical alveolar osteotomy to improve the axis of the incisors. After completing the presurgical orthodontic treatment, we performed Le Fort I and sagittal split ramus osteotomies to achieve a functional maxillo-mandibular relation. Improvements in angle measurements before presurgical and after postsurgical orthodontic treatment were: L1-Mn 92.0 improved to 81.5 degrees; L1-Oc 32.5 to 19.5; and interincisal angle improved from 111.0 to 131.5. We consider this method to be fascinating and outline of the representative case in this report.