3-dimensional analysis of hard- and soft-tissue symmetry in a Chinese population

Abstract

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. 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.

Photographic Parameters in Three-Dimensional Facial Image Acquisition. A Scoping Review

“…Despite the considerable quantity of image acquisition systems presently employed for 3D photography, research use for this type of imaging is limited to a handful of devices, of which 2 are the most extensively utilized. First, we found that the most used system was the 3dMD, 10,[12][13][14][15][16][17][18][19][20][21][22][23][24] which consists of 2 groups of 3 cameras, each located at 45 degrees to the right and left side target, and was used by 52% of the authors, followed by the Vectra M3, [25][26][27][28][29][30][31][32] which consists of a device composed of 3 groups of 2 cameras each and was used by 28% of the authors. In contrast, some other systems were used by some authors.…”

“…Baysal et al (2016) 48 and Dindaroğlu et al (2016) 49 reported that landmarks marked directly on the 3D facial file have higher reproducibility than those previously marked on the face. However, although most authors did not perform this premarking, using direct marking in the 3D files, 10,[13][14][15][16][17]19,21,[23][24][25][26][31][32][33][34][35]37,38,41 a large group of authors made the selection of points with a dermatograph pencil before making the images. 12,[27][28][29][30]36 Of all the articles analyzed, only Cassi et al (2018), 9 Parra and colleagues (2019), Zhou and colleagues (2023), Andrade and colleagues (2017), Wu and colleagues (2022), Bernini and colleagues (2020), Mc-Cormick et al (2021), 2 Godt and colleagues (2013), Baksi et al (2020), 1 and Zhao and colleagues (2023) evaluated the reproducibility of dot-marking, where a similar degree of reproducibility was observed in all studies, regardless of the dotmarking system used.…”