Symphysis morphology and mandibular alveolar bone thickness in patients with β-thalassemia major and different growth patterns

ABSTRACT Objective: The present study aimed to assess the morphology of symphysis and alveolar bone thickness (ABT) surrounding mandibular incisors in thalassemic patients, as compared to unaffected individuals. Methods: This case-control study was conducted on lateral cephalograms of 60 thalassemic and 60 unaffected patients with Class II malocclusion seeking orthodontic treatment at Dental School, Shiraz University of Medical Sciences. The sample was divided into three subgroups including hyperdivergent, normodivergent, and hypodivergent, according to the Jarabak index. Symphysis dimensions and alveolar bone thickness surrounding mandibular incisors were measured using AutoCad software. Finally, the correlation between alveolar bone thickness and symphysis morphology was assessed. Results: In general, chin dimensions and bone thickness at different levels of mandibular incisor roots (cervical, middle, apical) were smaller in thalassemic adolescents than controls. Concerning the total sample as well as the normodivergent subgroup, significantly lower values were observed in thalassemic patients for symphysis width, total ABT at the cervical, and lingual ABT at the apical root area compared to controls (p < 0.05). The hypodivergent growth pattern was not associated with any statistical differences between the groups (p> 0.05). In both thalassemic and control subjects, symphysis width showed a weak to moderate positive correlation with ABT of lower incisors (p< 0.05), whereas symphysis height showed a moderate positive correlation with cervical ABT in only ß‐thalassemia patients (p< 0.05). Conclusions: Compared to controls, ß-thalassemia patients showed thinner alveolar bone at different levels of lower incisor roots and smaller symphysis dimensions. There were significant correlations between symphysis dimensions and alveolar bone thickness of mandibular incisors in the sample.

摘要
目的：本研究旨在对比地中海贫血患者与健康人群下颌切牙周围的下颌联合形态及牙槽骨厚度（alveolar bone thickness, ABT）。
方法：本病例对照研究纳入了设拉子医科大学牙科学院正畸门诊中60例地中海贫血患者与60例安氏II类错𬌗畸形（Class II malocclusion）的健康对照者的头颅侧位片。根据贾拉巴克指数（Jarabak index），将样本分为高角、均角、低角三个亚组。使用AutoCAD软件测量下颌联合尺寸及下颌切牙周围的牙槽骨厚度。最终分析牙槽骨厚度与下颌联合形态之间的相关性。
结果：总体而言，地中海贫血青少年的颏部尺寸及下颌切牙根颈缘、根中、根尖各层面的骨厚度均小于健康对照组。就总样本及均角亚组而言，地中海贫血患者的下颌联合宽度、颈缘区总牙槽骨厚度及根尖区舌侧牙槽骨厚度均显著低于对照组（p < 0.05）。低角生长型组间未观察到统计学差异（p > 0.05）。在地中海贫血患者及健康对照人群中，下颌联合宽度与下颌切牙牙槽骨厚度均呈弱至中度正相关（p < 0.05）；而仅在β地中海贫血（ß‐thalassemia）患者中，下颌联合高度与颈缘区牙槽骨厚度呈中度正相关（p < 0.05）。
结论：与健康对照组相比，β地中海贫血患者的下颌切牙根各层面牙槽骨更薄，且下颌联合尺寸更小。本研究样本中，下颌联合尺寸与下颌切牙牙槽骨厚度存在显著相关性。