Teo Kui Fei, Nor Murshida Marizan, Mohamed Alizae Marny, Pritam Helmi Mohd Hadi
Orthodontic Discipline, Department of Family Oral Health, Faculty of Dentistry, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia.
Ministry of Health Malaysia, Putrajaya, Malaysia.
Anat Cell Biol. 2022 Dec 31;55(4):433-440. doi: 10.5115/acb.22.081. Epub 2022 Oct 17.
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 (<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 (<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 (<0.0001). Retroclined incisors exhibited taller and retroclined alveolar parts (<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.
本研究旨在通过几何形态测量分析，调查Ⅲ类骨面型患者下颌正中联合（MS）的一般形态变化。纳入了254例年龄在11至40岁之间、具有Ⅲ类骨面型（ANB＜1°）且下切牙角度＜99°的患者的治疗前头颅侧位片。使用TPSDig2软件在MS上确定具有x和y坐标的9个标志点，然后导入Morpho J进行形状和统计分析。主成分分析表明，三个主要形状维度的总方差为74.6%，代表了样本的大部分变异。普氏方差分析表明，Ⅲ类骨面型患者的MS形状主要受下颌角、切牙倾斜度和性别影响（＜0.0001）。典型变量分析表明，下颌角高的组MS明显更窄且拉长，而下颌角低的组MS更宽、呈球根状且圆润（＜0.0001）。下颌角低的组牙槽部分与基部部分的比例为1:5，下颌角高的组为2:3。与女性相比，男性的MS明显更高，B点区域更窄（＜0.0001）。切牙后倾的患者牙槽部分更高且后倾（＜0.0001）。Ⅲ类骨面型患者的MS形状在牙槽部分、基部部分或两者均有变化，并且受下颌角、切牙倾斜度和性别的影响。因此，了解MS的形状变化对于辅助正畸治疗计划很重要。
