[The effect of sagittal split ramus osteotomy advancement and setback mandible on occlusal force and masticatory efficiency].

21 patients (mandibular prognathism = 11, mandibular retrognathism = 10) whose occlusal force and masticatory efficiency were measured and analysed preoperatively, three and six months following sagittal split ramus osteotomy. The result shows that, in individuals with mandibular retrognathism treated by lengthening of the mandible, the occlusal force and masticatory efficiency would decrease, in individuals with mandibular prognathism treated by reduction in mandibular length, the occlusal force and masticatory efficiency would increase. There is no linear correlation relationship between the change of the occlusal force and the movement of the angle and the distance of the mandible.