Comparison of lower lip hypoesthesia between hybrid fixation and conventional fixation following sagittal split ramus osteotomy

PurposeThe purpose of this study was to compare the recovery period of lower lip hypoesthesia between hybrid fixation and conventional fixation using absorbable plates and screw systems following sagittal split ramus osteotomy (SSRO).Subjects and methodsThe subjects were 66 patients (132 sides) who underwent bilateral SSRO setback surgery. They were divided into a hybrid fixation group (66 sides, 1 u-HA/PLLA plate and 4 mono-cortical screws and a bi-cortical screw in each side) and a conventional fixation group (66 sides, 1 u-HA/PLLA plate and 4 mono-cortical screws in each side). Trigeminal nerve hypoesthesia at the region of the lower lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method.ResultsThe mean measurable periods were 8.1 ± 10.4 weeks in the hybrid fixation group, 5.1 ± 11.5 weeks in the conventional group with no significant difference. However, the maximum in the hybrid fixation group was 27 sides at 4 weeks postoperative and in the conventional fixation group was 37 sides at 1 week postoperative, and there was significant difference in the distribution of the measurable period (P < 0.0001).ConclusionThis study suggested that additional bi-cortical screws could affect the recovery of lower lip hypoesthesia after SSRO with bent absorbable plate fixation.