Maxillofac Plast Reconstr Surg.  2020;42(1):17. 10.1186/s40902-020-00260-9.

Quantification of three-dimensional facial asymmetry for diagnosis and postoperative evaluation of orthognathic surgery

Affiliations
  • 1Department of Oral and Maxillofacial Surgery, Dental Research Institute, School of Dentistry, Seoul National University, 101 Daehak-ro, Jongro-gu, Seoul 03080, South Korea
  • 2Onsam Dental Clinic, Seoul, South Korea
  • 3Seoul Sarang Dental Clinic, Seoul, South Korea
  • 4Department of Oral and Maxillofacial Surgery, Wonkwang University Hospital, Iksan, South Korea
  • 5Department of Oral and Maxillofacial Surgery, Chung-Ang University Hospital, Seoul, South Korea

Abstract

Background
To evaluate the facial asymmetry, three-dimensional computed tomography (3D-CT) has been used widely. This study proposed a method to quantify facial asymmetry based on 3D-CT.
Methods
The normal standard group consisted of twenty-five male subjects who had a balanced face and normal occlusion. Five anatomical landmarks were selected as reference points and ten anatomical landmarks were selected as measurement points to evaluate facial asymmetry. The formula of facial asymmetry index was designed by using the distances between the landmarks. The index value on a specific landmark indicated zero when the landmarks were located on the three-dimensional symmetric position. As the asymmetry of landmarks increased, the value of facial asymmetry index increased. For ten anatomical landmarks, the mean value of facial asymmetry index on each landmark was obtained in the normal standard group. Facial asymmetry index was applied to the patients who had undergone orthognathic surgery. Preoperative facial asymmetry and postoperative improvement were evaluated.
Results
The reference facial asymmetry index on each landmark in the normal standard group was from 1.77 to 3.38. A polygonal chart was drawn to visualize the degree of asymmetry. In three patients who had undergone orthognathic surgery, it was checked that the method of facial asymmetry index showed the preoperative facial asymmetry and the postoperative improvement well.
Conclusions
The current new facial asymmetry index could efficiently quantify the degree of facial asymmetry from 3D-CT. This method could be used as an evaluation standard for facial asymmetry analysis.

Keyword

Facial asymmetry; Three-dimensional computed tomography; Orthognathic surgery
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