A comparison of postoperative hypoesthesia between two types of sagittal split ramus osteotomy and intraoral vertical ramus osteotomy, using the trigeminal somatosensory-evoked potential method.

The purpose of this study was to evaluate hypoesthesia of the lower lip using trigeminal somatosensory-evoked potential following 2 types of sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy (IVRO). There were 30 patients with mandibular prognathism, with and without asymmetry, who were divided into three groups: the Obwegeser method (Ob) group, the Obwegeser-Dal Pont method (ODP) group and the intraoral vertical ramus osteotomy (IVRO) group. The trigeminal somatosensory-evoked potential was recorded in the region of the lower lip and evaluated preoperatively and postoperatively. The average recovery periods from lower lip hypoesthesia in the IVRO and the Ob group were significantly shorter than in the ODP group (P<0.05). In conclusion, IVRO showed the earliest recovery from hypoesthesia or an absence of hypoesthesia, and lower lip hypoesthesia was less with the Ob method than the ODP method.