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KJO Korean Journal of Orthodontics

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eISSN 2005-372X
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Korean J Orthod

Published online September 1, 2021

Copyright © The Korean Association of Orthodontists.

Characterization of Facial Asymmetry Phenotypes in Adult Patients with Skeletal Class III Malocclusion Using Three-Dimensional Computed Tomography and Cluster Analysis

Sang-Woon Ha a ; Su-Jung Kim b; Jin-Young Choi c; Seung-Hak Baek d

a Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Republic of Korea; Orcid number: 0000-0002-6069-9947
b Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Republic of Korea.
c Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Seoul, Republic of Korea;
d Department of Orthodontics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Republic of Korea; Orcid number: 0000-0002-6586-9503

Correspondence to:Seung-Hak Baek. Professor, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, Daehak-ro #101, Jongno-gu, Seoul, 03080, Republic of Korea. Tel: +82-2-2072-3952; e-mail: drwhite@unitel.co.kr

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: To classify facial asymmetry (FA) phenotypes in adult patients with skeletal Class III (C-III) malocclusion.
Materials and methods: The samples consisted of 120 C-III patients who underwent orthognathic surgery (OGS) and whose three-dimensional computed tomography (3D-CT) images were taken one month prior to OGS. Thirty hard tissue landmarks were identified. After measurement of 22 variables including cant (°, mm), shift (mm), and yaw (°) of the maxilla, maxillary dentition, mandibular dentition, mandible, and mandibular border and differences in the frontal ramus angle (FRA, °) and ramus height (RH, mm), K-means cluster analysis was conducted using three variables [cant in the maxillary dentition (Max-dent, mm) and shift (mm) and yaw (°) in the mandibular border (Man-border)]. Statistical analyses were conducted to characterize the differences in the FA variables among the clusters.
Results: The FA phenotypes were classified into five: 1) non-asymmetry type (35.8%); 2) maxillarycant type (14.2%; severe cant of the Max-dent, mild shift of the Man-border); 3) mandibular-shift and yaw group (16.7%; moderate shift and yaw of the Man-border, mild RH-difference); 4) complex type (9.2%; severe cant of the Max-dent, moderate cant, severe shift, and severe yaw of the Man-border, moderate differences in FRA and RH); and 5) maxillary reverse-cant type (24.2%; reverse-cant of the Max-dent). Strategic decompensation by pre-surgical orthodontic treatment and considerations for OGS planning were proposed according to the FA phenotypes.
Conclusion: This FA phenotype classification might be an effective tool for differential diagnosis and setting a proper surgical planning for Class III patients with FA.

Keywords: facial asymmetry, Class III malocclusion, cluster analysis

Article

ahead

Korean J Orthod

Published online September 1, 2021

Copyright © The Korean Association of Orthodontists.

Characterization of Facial Asymmetry Phenotypes in Adult Patients with Skeletal Class III Malocclusion Using Three-Dimensional Computed Tomography and Cluster Analysis

Sang-Woon Ha a ; Su-Jung Kim b; Jin-Young Choi c; Seung-Hak Baek d

a Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Republic of Korea; Orcid number: 0000-0002-6069-9947
b Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Republic of Korea.
c Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Seoul, Republic of Korea;
d Department of Orthodontics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Republic of Korea; Orcid number: 0000-0002-6586-9503

Correspondence to:Seung-Hak Baek. Professor, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, Daehak-ro #101, Jongno-gu, Seoul, 03080, Republic of Korea. Tel: +82-2-2072-3952; e-mail: drwhite@unitel.co.kr

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: To classify facial asymmetry (FA) phenotypes in adult patients with skeletal Class III (C-III) malocclusion.
Materials and methods: The samples consisted of 120 C-III patients who underwent orthognathic surgery (OGS) and whose three-dimensional computed tomography (3D-CT) images were taken one month prior to OGS. Thirty hard tissue landmarks were identified. After measurement of 22 variables including cant (°, mm), shift (mm), and yaw (°) of the maxilla, maxillary dentition, mandibular dentition, mandible, and mandibular border and differences in the frontal ramus angle (FRA, °) and ramus height (RH, mm), K-means cluster analysis was conducted using three variables [cant in the maxillary dentition (Max-dent, mm) and shift (mm) and yaw (°) in the mandibular border (Man-border)]. Statistical analyses were conducted to characterize the differences in the FA variables among the clusters.
Results: The FA phenotypes were classified into five: 1) non-asymmetry type (35.8%); 2) maxillarycant type (14.2%; severe cant of the Max-dent, mild shift of the Man-border); 3) mandibular-shift and yaw group (16.7%; moderate shift and yaw of the Man-border, mild RH-difference); 4) complex type (9.2%; severe cant of the Max-dent, moderate cant, severe shift, and severe yaw of the Man-border, moderate differences in FRA and RH); and 5) maxillary reverse-cant type (24.2%; reverse-cant of the Max-dent). Strategic decompensation by pre-surgical orthodontic treatment and considerations for OGS planning were proposed according to the FA phenotypes.
Conclusion: This FA phenotype classification might be an effective tool for differential diagnosis and setting a proper surgical planning for Class III patients with FA.

Keywords: facial asymmetry, Class III malocclusion, cluster analysis