Exploration Of Related Hard Tissues Parameters That Affect The Subjective Perception Of Facial Symmetry After Orthognathic Surgery In Skeletal Class Ⅲ Patients With Facial Asymmetry

ObjectivesFacial asymmetry is common in the population,but surgery is required in severe facial asymmetry.However,Prevalence of facial asymmetry in skeletal Class Ⅲ patients is quite high.For these patients,Orthodontic-Orthognathic combinatioin therapy is usually the best treatment.Although skeletal Class Ⅲ patients with facial asymmetry can be greatly improved after orthognathic surgery,there are still some patients who still feel facial asymmetry.This is not only due to a gap between patients and doctors in assessing facial asymmetry,but also due to the unknown relationship between the subjective perception of facial asymmetry and the objective measurement of jaw hard tissues.So far,there are relatively few studies on the hard tissue factors related to subjective perception of facial asymmetry,but this is very important,so this experiment was designed.This experiment retrospectively analyzed 16 cases of skeletal Class Ⅲmalocclusion with facial asymmetry and double jaw surgery.The preoperative and postoperative CT of the case was reconstructed by three-dimensional reconstruction,and the 7 midline items of the hard tissue and 17 pairs of bilateral items were measured,and the symmetry of the hard tissue was analyzed.Method of expert subjective perception scoring was used,the facial symmetry of the case was scored,and the correlation between the subjective perception score and the symmetry of hard tissue was explored for Providing reference for clinical workMethodsExperiment one:The CT data six months after undergoing orthognathic surgery of 16 patients were collected and imported into mimics20.0.The soft tissues of each patient were reconstructed,and three experienced orthognathic doctors subjectively scored their facial symmetry,and the patients were divided into groups based on the postoperative subjective score.Experiment 2:The CT data of 16 patients before and half a year after orthognathic surgery was collected and imported into mimics20.0 software,the cranio-maxillofacial three-dimensional model was reconstructed,then a reference plane was established,and midline and bilateral measurements before and after surgery was carried out.According to the grouping,SPSS21 software was used to analyze the data to explore the changes in the symmetry of hard tissues after orthognathic surgery.Experiment 3:Spss21 was used to analyze the correlation between the postoperative subjective perception score and each measurement item to explore the relevant hard tissue factors that affect the subjective perception of facial symmetry.ResultsExperiment 1:Among the 16 eligible cases collected,there were 8 males and 8 males,with an average age of 20.94 years.According to the results of postoperative subjective perception scores,8 patients were classified into the symmetric group(average score of 4.42),and 8 patients were classified into the asymmetric group(average score of 3.42).There was a significant difference in the scores between the two groups(P<0.05)).Experiment 2:According to the grouping of the symmetric group and the asymmetric group,the Mann-Whitney U test was performed on the midline and bilateral measurement items of the two groups before and after the operation.It can be obtained that the results of the measurement items of the mandibular midline,the symmetry of the upper jaw occlusal plane,the symmetry of the mandibular ascending ramus before and after the operation,the morphological symmetry of the chin and the symmetry of the contour of the lower mandibular after the operation are significantly different.Experiment 3:The results of correlation analysis showed that the postoperative subjective perception score is significantly correlated to the measurement items of the mandibular midline,the symmetry of the maxillary occlusal plane,the symmetry of the mandibular ascending ramus before and after the surgery,the morphological symmetry of the chin,and the symmetry of the contour of the mandibular lower edge after surgery.Conclusions1.Patients with skeletal Class Ⅲ and facial asymmetry may still have facial asymmetry after orthognathic surgery;2.The deviation of the the mandibular midline mark points will affect the subjective perception of postoperative facial symmetry;3.The transverse cant of the maxillary occlusal plane will affect the subjective perception of postoperative facial symmetry;4.The symmetry of the ascending mandibular ramus will affect the subjective perception of facial symmetry after surgery;5.The symmetry of the chin shape and the symmetry of the submandibular contour will affect the subjective perception of postoperative facial symmetry.