Evaluation of factors affecting recovery period in lower lip hypoesthesia after sagittal split ramus osteotomy in mandibular prognathism patients

PurposeThe purpose of this study was to evaluate the factors affecting the recovery period of lower lip hypoesthesia after sagittal split ramus osteotomy (SSRO) in mandibular prognathism patients using multivariate analysis, retrospectively.Subjects and methodsThe subjects were 222 patients (444 sides) who underwent bilateral SSRO setback surgery with and without Le Fort I osteotomy. Trigeminal nerve hypoesthesia at the region of the lower lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method pre- and post-operatively. Recovery period was determined as the time when TSEP was first measurable post-operatively. Age, sex, presence or absence of third molars, setback amount and osteotomy type and fixation method were selected as covariates in the multivariate analysis. The factor affecting the recovery period in lower lip hypoesthesia was examined with Cox's proportional hazard regression.ResultsSex and osteotomy fixation method affected the recovery period in lower lip hypoesthesia significantly (P = 0.0132 and P = 0.0394). However, the other factors did not affect the recovery period.ConclusionThis study suggested that sex and osteotomy type and fixation method may affect the recovery period in lower lip hypoesthesia after SSRO setback surgery.