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Anat Cell Biol

Published online October 17, 2022

https://doi.org/10.5115/acb.22.081

Copyright © Korean Association of ANATOMISTS.

Geometric morphometric analysis of mandibular symphysis in Class III skeletal base

Kui Fei Teo1,2 , Murshida Marizan Nor1 , Alizae Marny Mohamed1 , Helmi Mohd Hadi Pritam3

1Orthodontic Discipline, Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Kuala Lumpur, 2Ministry of Health Malaysia, Putrajaya, 3School of Health Sciences, Universiti Sains Malaysia, Kelantan, Malaysia

Correspondence to:Murshida Marizan Nor
Orthodontic Discipline, Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Kuala Lumpur 50300, Malaysia
E-mail: murshida@ukm.edu.my

Received: April 12, 2022; Revised: May 11, 2022; Accepted: May 12, 2022

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

This study aimed to investigate the general mandibular symphysis (MS) shape variation among Class III skeletal base, using geometric morphometric analysis. Pre-treatment lateral cephalometric radiographs of 254 patients aged 11–40 years old, with Class III skeletal base (ANB <1°) and lower incisor angle (<99°) were included. Nine-landmarks with x and y coordinates were identified on MS using TPSDig2 software, then exported into Morpho J for shape and statistical analysis. Principal component analysis showed that three main shape dimensions with a total variance of 74.6% represented the majority variation of samples. Procrustes Anova showed the shape of MS in Class III skeletal base to be mainly influenced by gonial angle, incisor inclination and sex (P<0.0001). Canonical variate analysis showed that high gonial angle groups had significantly narrower and elongated MS whereas low gonial angle groups had wider, bulbous and rounded MS (P<0.0001). The ratio of alveolar part to basal part was 1:5 in low gonial angle and 2:3 in high gonial angle. Males had significantly taller MS with narrower B point area compared to females (P<0.0001). Retroclined incisors exhibited taller and retroclined alveolar parts (P<0.0001). The shape of MS in Class III skeletal base varied at the alveolar part, basal part or both and it is influenced by gonial angle, incisor inclination and sex. Hence, understanding the shape variation of MS is important to aid orthodontic treatment planning.

Keywords: Geometric morphometric, Mandibular symphysis, Class III, Gonial angle, Shape

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