Long-term stability following surgical orthodontic treatment of mandibular prognathisms: investigation by means of lateral X-ray cephalogram.

: The purpose of this study was to investigate the long-term stability of jaw relations and occlusion following surgical orthodontic treatment of mandibular prognathisms and skeletal openbites. Subjects consisted of fifteen adult patients. Ten patients underwent the sagittal split ramus osteotomy (SSRO) of the mandible and five patients underwent two jaw surgery (Le Fort I osteotomy of the maxilla and SSRO of the mandible). They were observed over five years after the end of active treatment, and lateral X-ray cephalograms were taken at each stage. In the SSRO group, pogonion was retrograded an average of 8.7mm due to the operation and it was further replaced 0.4mm backward after the end of active treatment. Although the vertical distance between nasion and menton decreased 2.9mm between the operative period, it increased 1.8mm after the end of active treatment. On the other hand, in the two jaw surgery group, point A was advanced 4.0mm forward and < SNA increased 3.1 degrees between the operative period. Pogonion was retrograded 11.4mm between the same period, but moved 0.7mm forward after the end of active treatment. A comparison of the osteosynthesis methods revealed that pogonion in the wiring group was retrograded 8.3mm backward between the operative period, but moved 2.1mm forward during the postsurgical orthodontic treatment. Pogonion in the rigid group was retrograded 12.6mm backward between the operative period, but moved 1.6mm forward during the postsurgical orthodontic treatment. However, both groups were stabilized completely after the end of active treatment. A comparison of the differences in the orthodontic treatment method revealed that < Ul-SN in the extraction group inclined 8.3 degrees lingually during presurgical orthodontic treatment, but it tipped 7.0 degrees labially during the postsurgical orthodontic treatment and inclined 3.4 degrees lingually after the end of active treatment. < Ul-SN in the non-extraction group inclined 5.5 degrees lingually during the presurgical orthodontic treatment, but it tipped 2.0 degrees labially during the postsurgical orthodontic treatment and inclined 1.9 degrees lingually after the end of active treatment.