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Objectives: We used three-dimensional (3D) virtual images to undertake a subjective evaluation of how different factors affect the perception of facial asymmetry among orthodontists and laypersons with the aim of providing a quantitative reference for clinics. Materials and methods: A 3D virtual symmetrical facial image was acquired using FaceGen Modeller software. The left chin, mandible, lip and cheek of the virtual face were simulated in the horizontal (interior/exterior), vertical (up/down), or sagittal (forward or backward) direction in 3, 5, and 7 mm respectively with Maya software to increase asymmetry for the further subjective evaluation. A pilot study was performed among ten volunteers and 30 subjects of each group were expected to be included based on 80% sensitivity in this study. The sample size was increased by 60% to exclude incomplete and unqualified questionnaires. Eventually, a total of 48 orthodontists and 40 laypersons evaluated these images with a 10-point visual analog scale (VAS). The images were presented in random order. Each image would stop for 30 s for observers with a two-second interval between images. Asymmetry ratings and recognition accuracy for asymmetric virtual faces were analyzed to explore how different factors affect the subjective evaluation of facial asymmetry. Multivariate linear regression and multivariate logistic regression models were used for statistical data analysis. Results: Orthodontists were found to be more critical of asymmetry than laypersons. Our results showed that observers progressively decreased ratings by 1.219 on the VAS scale and increased recognition rates by 2.301-fold as the degree of asymmetry increased by 2 mm; asymmetry in the sagittal direction was the least noticeable compared with the horizontal and vertical directions; and chin asymmetry turned out to be the most sensitive part among the four parts we simulated. Mandible asymmetry was easily confused with cheek asymmetry in the horizontal direction. Conclusions: The degree, types and parts of asymmetry can affect ratings for facial deformity as well as the accuracy rate of identifying the asymmetrical part. Although orthodontists have higher accuracy in diagnosing asymmetrical faces than laypersons, they fail to correctly distinguish some specific asymmetrical areas. [ABSTRACT FROM AUTHOR]

Background: Facial symmetry severely affects appearance and function. Large numbers of patients seek orthodontic treatment to improve facial symmetry. However, the correlation between hard- and soft-tissue symmetry is still unclear. Our aim was to investigate the hard- and soft-tissue symmetry in subjects with different levels of menton deviation and sagittal skeletal classes with 3D digital analysis and to investigate the relationship between the entire and individual hard- and soft-tissues. Methods: A total of 270 adults (135 males and 135 females) consisting of 45 subjects of each sex in each sagittal skeletal classification group. All subjects were further classified into relative symmetry (RS), moderate asymmetry (MA) and severe asymmetry (SA) groups based on the degree of menton deviation from the mid-sagittal plane (MSP). The 3D images were segmented into anatomical structures and mirrored across the MSP after establishing a coordinate system. Original and mirrored images were registered by a best-fit algorithm, and the corresponding root mean square (RMS) values and colormap were obtained. The Mann‒Whitney U test and Spearman correlation were conducted for statistical analysis. Results: The RMS increased with greater deviations with regard to the deviation of the menton in most of anatomical structures. Asymmetry was represented in the same way regardless of sagittal skeletal pattern. The soft-tissue asymmetry had a significant correlation with dentition in the RS group (0.409), while in the SA group, it was related to the ramus (0.526) and corpus (0.417) in males and was related to the ramus in the MA (0.332) and SA (0.359) groups in females. Conclusions: The mirroring method combining CBCT and 3dMD provides a new approach for symmetry analysis. Asymmetry might not be influenced by sagittal skeletal patterns. Soft-tissue asymmetry might be reduced by improving the dentition in individuals with RS group, while among those with MA or SA, whose menton deviation was larger than 2 mm, orthognathic treatment should be considered. [ABSTRACT FROM AUTHOR]

PURPOSE: The purpose of this study was to investigate the relationship between unilateral temporomandibular joint disk displacement without reduction and facial symmetry. METHODS: 17 individuals (aged from 13 to 28), including 15 females and 2 males, with unilateral TMJ disk displacement without reduction were included. Computerized tomography scans were performed for each patient. Three-dimensional virtual skulls were reconstructed from CT data with Simplant11.04 software. Measuring points were defined on facial skeleton as well as teeth. We set Frankfort horizontal plane and sagital plane as reference planes. Asymmetric character of glenoid fossa region, mandible and maxillary occlusal plane cant were observed. The three-dimensional data of normal side and disk displacement side was analyzed by paired t tests with SPSS11.0 software package. RESULTS: It was observed that the vertical position of Po (the most superior point of the external auditory canal), ArE (crest of the articular eminence) and GIF (roof of glenoid fossa) in disk displacement side was significantly more inferior than the normal side (P<0.05). Subjects with unilateral TMJ disk displacement without reduction had shorter condylar height(P<0.01), shorter ramus height (P<0.01) and shorter mandibular body (P<0.05) in disk displacement side compared with normal side. The mandibular midpoint deviated toward the disk displacement side ranging from 0.72ram to 7.66mm (mean 3.62±2.49mm). In addition, all of those subjects had eanted maxillary occlusal planes. CONCLUSIONS: Unilateral TMJ disk displacement without reduction might cause facial asymmetry. Glenoid fossa region, mandible and maxillary occlusal plane were involved in. The results indicate that the amount of asymmetry appear mainly in condylar height. Supported by Shanghai Leading Academic Discipline Project (Grant No.Y0203). [ABSTRACT FROM AUTHOR]

The facial asymmetry associated with vertical maxillary excess and mandibular prognathism is one of the more complicated types in the field of oral and maxillofacial surgery. The purpose of this study was to investigate the efficacy of combined orthognathic surgeries, together with guiding templates and splints fabricated by rapid prototyping technique, for the correction of facial asymmetry. Fourteen patients with facial asymmetry associated with vertical maxillary excess and mandibular prognathism were included. A maxillary Le Fort I osteotomy, a sagittal split ramus osteotomy on the shorter side of the face, and an intraoral vertical ramus osteotomy on the longer side of the face were performed with the aid of guiding templates and splints fabricated by rapid prototyping technique. Parameters reflecting maxillary canting, ramal inclination, mandibular deviation, and chin inclination were measured before surgery, 7 days after surgery, and 1 year after surgery, and compared. Significant differences in these parameters were found between the two sides preoperatively, whereas no differences were observed postoperatively. Facial asymmetry was corrected in all patients with satisfactory outcomes. In conclusion, combined orthognathic surgery and guiding templates and splints can offer improvements in accuracy, complexity, and duration over traditional procedures for the correction of facial asymmetry associated with vertical maxillary excess and mandibular prognathism., (Copyright © 2015 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

Three experiments were carried out to analyze the component processes contributing to observed asymmetries in face perception, to determine whether these asymmetries occur for complex visuospatial stimuli other than human faces, and to investigate the effects of expertise on the asymmetries. Two component processes contributed to the observed asymmetries: perceptual bias (PB) in the observer and face asymmetries (FA). There was no PB effect for complex visuospatial stimuli other than human faces (landscapes, abstract paintings and animal faces). Expertise effects were investigated by examining the judgments of Chinese and Caucasian subjects for own-race and other-race faces. A PB was found for both Caucasian and Chinese faces, but the size of the effect was not related unequivocally to expertise. Caucasian subjects showed a PB for own-race faces only, but Chinese subjects showed a PB for both Chinese and Caucasian faces. There was no FA effect for Chinese faces, even when the composites were perceived as more dissimilar than the Caucasian composites, for which there was an FA effect. The implications of these results for the theoretical interpretation of perceptual asymmetries are discussed.