Three-dimensional assessment of facial asymmetry

Abstract

Facial appeal influences perceptions about an individual as well as their patterns of social interactions. It can be inferred from the literature that life is more amiable and delightful for attractive individuals. Any distortions in the facial forms from the societal standards is considered to be a social ailment. Along with the social challenges the subjects affected with facial asymmetry face mental and functional distress. Fortunately, orthodontics in conjugation with orthognathic surgery has offered an exit from the suffering of this targeted population. However precise knowledge of anatomy via three-dimensional (3D) sources becomes a prerequisite for accurate diagnosis and determination of the course of treatment which in turn influences the outcomes of the treatment. Given that, we conducted systematic reviews focusing on the diagnosis and treatment outcomes with an aim to systematically review various methods used to construct an ideal mid-sagittal plane for accurate assessment of facial asymmetry and to investigate the soft tissue response with the underlying osseous movement post-surgery in patients with facial asymmetry respectively. The result of our first systematic review revealed the importance of stable landmarks in the construction of the mid-sagittal plane either by cephalometric or morphometric method. The second systematic review showed that although the post-surgical changes of the hard and soft tissue are similar in pattern but vary in magnitude as the soft-tissue movement is lesser than the osseous structures. Based on the findings of the systematic reviews two studies were performed targeting the same aspects. The first study intended towards identifying the site and severity of any facial asymmetry prior and post to orthognathic surgery in subjects with facial asymmetry. The results of this study showed that in asymmetry group, bilateral landmarks exhibited significant deviation in the mandible and midface regions. Before surgery, asymmetry was more severe at the mandibular midline and sites close to it, in the asymmetry group. Bimaxillary surgery proved to be highly effective, with a significant correction of the menton to a clinically normal value (2.90 mm, p < 0.001). After surgery, significant residual asymmetry was observed at the mental foramen (p = 0.001) in the R-L direction. Moreover, significant asymmetry persisted at the sigmoid notch (p = 0.001) in the S-I direction. And the second study was designed to evaluate the outcomes of corrective surgical treatment for craniofacial asymmetry using four different methods with the aim to develop the best technique for craniofacial asymmetry assessment. With this study we were able to introduce a novel method (Modified Procrustes Analysis) for the quantification of facial asymmetry which showed some promising results that were comparable to Asymmetry Index and Clinically Derived Midline, making it a more viable option for craniofacial asymmetry assessment. Comprehensive 3D presurgical planning is central for asymmetry correction which is highly influenced by the accuracy of the knowledge of the sites and the degree of asymmetry. Therefore a technique with more valid clinical representation should be employed for successful treatment outcomes.