The Study Of The Facial Asymmetry And Correlation In Soft And Hard Tissue With CBCT

Objectives: The aim of the present study was to compare the differences of the analysis on facial symmetry by three different types of mid-sagittal plane using CBCT and to discuss the symmetry and correlation between the maxillofacial hard and soft tissue.Methods: Twenty-one patients with facial asymmetry were selected as experimental group and twenty-one patients without facial asymmetry were selected as control. The CBCT images of each patient were collected before the therapy, and then the three-dimensional reconstruction was done with Dolphin software. Three different methods were used to establish three types of mid-sagittal plane and measure the Me deviation for each mid-sagittal plane, respectively. The differences of the three types of mid-sagittal plane in Me deviation were analyzed by ANOVA. Nine orthodontists and postgraduates were selected to evaluate the mid-sagittal planes which had been obtained from the three different methods. The differences of subjective opinions among the three types of mid-sagittal plane were compared by Friedman-M.Thirty maxillofacial hard and soft tissue landmarks of the patients were located on the three-dimensional reconstructive images. The coordinates of each landmark were obtained and asymmetry index was calculated. The differences of hard and soft tissue asymmetric index between the experimental group and controlled group were analyzed. The correlation between maxillofacial hard and soft tissue asymmetric index and the differences between each hard tissue asymmetric index and the corresponding soft tissue asymmetric index both in experimental and controlled groups were calculated.Results: In experimental group, the Me deviation measurements from method A and method B, from method A and method C were significantly different. For the subjective opinion, in experimental group, there is significant difference among the three methods, and method C is the best while method B was the worst. In controlled group, there is significant difference between method B and method C. Among them, method A and method C are better than method B.The asymmetric index of the maxillofacial hard and soft tissue landmarks tend to increase gradually from the upper to lower face, generally. The experimental group of asymmetric index in Lil, Pog, Me, UFM, LFM, Co, Go, Li, Pog’, Me’, Ch and Go’ had a significant difference with the controlled group(P<0.05), and the experimental group was larger than the controlled group.In experimental group, several landmarks were correlated with each other. Pog, Lil, Me, LFM were correlated with each other(P<0.05). Pog, Me, Go were correlated with each other(P<0.05). Li, Pog’, Me’, Ch were correlated with each other(P<0.05). Lil, Pog, Me, LFM, Go, Li, Pog’, Me’, Ch, Go’ were correlated(P<0.05).In controlled group, several landmarks were correlated with each other. Lil, Pog, Me, Go were correlated with each other(P<0.05). Li, Pog’, Me’, Go’ were correlated with each other(P<0.05). Lil, Pog, Me, Li, Pog’, Me’ were correlated(P<0.05).In both groups, there was significant asymmetric index difference between Na and Na’, ANS and Sn, Pog and Pog’, Me and Me’, Go and Go’(P<0.05). In experimental group, there was significant difference between LFM and Ch(P<0.05).The ratios of hard tissue and corresponding soft tissue asymmetric index were different in different part.Conclusion: Evaluation of the deviation is different with the different mid-sagittal planes established by different methods and landmarks. Asymmetry mainly exists on the mandibular and the lower face. There is correlation and difference between the soft tissue asymmetry and the hard tissue asymmetry. Hard tissue asymmetry is compensated by the soft tissue to some extent.