Changes Of Lip Symmetry In Laterognathism Cases After 2-Jaw Orthognathic Surgery

Objective:Due to the asymmetrical development of the maxilla and mandible,the position and direction of the muscles attached to them are shifted and changed,and the dynamic balance of the perioral muscles is out of balance,resulting in lip deformity,which greatly influences the facial appearance of the patient.Orthognathic surgery can correct dental and maxillofacial deformities by repositioning the upper and lower jaws.Changes in the position of the jaws will lead to changes of the corresponding soft tissues and then improve lip asymmetry.This study aims to investigate and quantify the influence of skeletal changes on lip asymmetry correction in 2-jaw orthognathic surgery for laterognathism cases.Methods : This study was a retrospective study,patients who diagnosed with laterognathism of the mandible and underwent Le Fort I osteotomy and bilateral sagittal mandibular ramus osteotomy in Hospital of Stomatology,China Medical University from May 2021 to July 2022 were enrolled to participate in this study.CT scanning was required for all subjects 7 days before operation and 6 months or more after operation,and exported in DICOM format.Import the data into Proplan CMF3.0 software to reconstruct and measure the soft tissue skull model and hard tissue jaw model.Import the measured values into IBM SPSS Statistics 26.0 software for data analysis.Pearson correlation test was used to analyze the correlation between soft and hard tissue changes.Multiple linear regression analysis was applied to obtain the linear relationship between jaw position changes and lip symmetry changes Results:After inclusion and exclusion screening,a total of 22 patients entered the final statistics,with an average age of 20.82±3.28 years.All 22 patients underwent surgery successfully.After treatment,lip asymmetry was significantly improved.The results of Pearson correlation analysis showed that the correction of the horizontal deviation of the maxilla and the deviation of pogpnino and menton were significantly related to the improvement of lip asymmetry,and the difference was statistically significant(P<0.01).The results of multiple linear regression analysis showed that for every 1mm correction of the difference in the distance between the mesiobuccal cusp of the maxillary first molars and the MSR plane,the deviation of the upper lip was corrected by 0.188 mm.For every 1mm correction of pogpnino deviation,the difference between the cheilion of both sides and the FH plane is reduced by0.273 mm,the deviation of the lower lip was corrected by 0.374 mm,and the deviation of the lower lip relative to the upper lip is 0.313 mm.Conclusions:For lip asymmetry caused by the upper and lower jaw asymmetry,the lip asymmetry can be fully corrected by correcting the maxillary deviation and guiding the pogpnino to the midline through 2-jaw orthognathic surgery.