Facial asymmetry assessment in skeletal Class III patients with spatially-dense geometric morphometrics

Abstract

Summary Objective Quantification and visualization of the location and magnitude of facial asymmetry is important for diagnosis and treatment planning. The objective of this study was to analyze the asymmetric features of the face for skeletal Class III patients using spatially-dense geometric morphometrics. Methods Three-dimensional facial images were obtained for 86 skeletal Class III patients. About 7160 uniformly sampled quasi-landmarks were automatically identified on each face using template mapping technique. The pointwise surface-to-surface distance between original and mirror face was measured and visualized for the whole face after robust Procrustes superimposition. The degree of overall asymmetry in an individual was scored using a root-mean-squared-error. Automatic partitioning of the face was obtained, and the severity of the asymmetry compared among seven facial regions. Results Facial asymmetry was mainly located on, but not limited to, the lower two-thirds of the face in skeletal Class III patients. The lower cheek and nose asymmetry were detected to have more extensive and of a greater magnitude of asymmetry than other facial anatomical regions but with various individual variations. The overall facial asymmetry index and the regional facial asymmetry indices were higher in males and patients with chin deviation. Conclusions Soft tissue asymmetry is predominately presented in the lower-third of the face in skeletal Class III patients and with various variations on other facial anatomical regions. Morphometric techniques and computer intensive analysis have allowed sophisticated quantification and visualization of the pointwise asymmetry on the full face.

3D facial mask for facial asymmetry diagnosis

“…To further verify the utility of this method, patients with facial asymmetry were recruited, and a 3D facial mask evaluation and mirror and overlap analysis were conducted. Mirror and overlap analysis is a standard method for assessing facial asymmetry by superimposing an original 3D facial image on its mirror copy [ 53 ]. This method has been previously described and is regarded as a relatively reliable diagnostic method [ 9 , [32] , [33] , [34] ].…”

Subjective evaluation of facial asymmetry with three-dimensional simulated images among the orthodontists and laypersons: a cross-sectional study

“…There is a strong possibility that patients in reality have deviations in more than one part of the face in a variety of directions because the human face possesses a diversity of muscles on each side, which form a complex interdependent system to produce changes in the superficial geometry of the face and contribute to a wide range of functions [ 27 ]. For instance, mandible asymmetry may affect the depressor anguli oris, mentalis and depressor labii inferioris muscles, which are attached to the mandible and consist of the lip, and then stretch the orbicularis oris and the cutis to the deviated side, resulting in lip asymmetry [ 11 ]. Future research should examine more specific and complicated facial asymmetry to better imitate clinical conditions.…”

“…The zygion region is regarded as a delicate component of the face, the protrusion of which is crucial to achieve smooth lateral facial aesthetic lines. Moreover, studies have shown that the cheek has higher asymmetry indices than other anatomical regions probably due to varieties of masticatory muscles [ 11 ]. Thus, in our study, we selected the chin (including the soft tissue of the mental tubercle and peripheral region), mandible (including the soft tissue gonion and peripheral region), lip (including the cheilion and peripheral region) and cheek (including the soft tissue zygion and peripheral region) to simulate in different directions and to study how different parts and directions might affect the perception of facial asymmetry.…”

An Automated Method of 3D Facial Soft Tissue Landmark Prediction Based on Object Detection and Deep Learning

“…Additionally, these landmarks serve as crucial reference points and the foundation for the diagnosis, treatment, and evaluation of clinical work [1][2][3]. Facial landmarks serve a crucial function in facilitating tooth alignment, establishing the occlusal vertical distance, determining the 3D median sagittal plane, analyzing maxillofacial asymmetry [4], aiding in preoperative analysis, surgical design, postoperative prediction, and the efficacy evaluation of orthognathic surgery [5,6].…”