下颌第二磨牙近中阻生的局部牙列及颌骨形态的三维分析

Three dimensional analysis of localized dentition and mandibular morphology in patients with mesio-impacted mandibular second molars

目的通过CBCT三维测量比较下颌第二磨牙近中阻生患者与非阻生患者下颌第二磨牙区域牙列及颌骨形态的差异,分析下颌第二磨牙近中阻生患者的局部牙列及下颌骨形态特征。方法选取下颌第二磨牙近中阻生与非阻生患者总计148例,共分为三组,第一组(G1):下颌第二磨牙单侧阻生患者(50例);第2组(G2):双侧阻生患者(48例);第3组(G3):对照组(50例)。收集患者治疗前的CBCT影像,共测量15个指标并进行统计学分析,其中牙性指标10个,骨性指标5个。结果单侧及双侧阻生患者下颌第二磨牙牙冠长度、宽度均大于对照组,而萌出间隙颌骨高度均小于对照组;双侧阻生患者萌出间隙长度及宽度均显著小于单侧阻生患者;单侧阻生患者萌出间隙长度及高度均小于非阻生侧(P<0.05)。结论下颌第二磨牙近中阻生患者下颌第一磨牙、第二磨牙牙冠相对较大;下颌第二磨牙近中阻生患者萌出间隙不足,且双侧阻生较单侧萌出间隙不足更为严重,而下颌第三磨牙的存在及性别差异与下颌第二磨牙近中阻生无显著关联。

Objective To investigate the morphological differences of localized dentition and mandible between patients with mesioimpacted mandibular second molars(MM2)and non-impacted patients in three dimensions and analyze the morphological characteristics.Methods A total of 148 patients who underwent cone-beam computed tomography(CBCT)were included and divided into three groups.Group 1(G1)included 50 patients with unilaterally mesio-impacted MM2;group 2(G2)was composed of 48 patients with bilaterally mesio-impacted MM2,and group 3(G3)was made up of 50 age-and gender-matched controls.Fifteen measurements were selected,including 10 dental measurements and 5 bony measurements.Results The length and width of MM2 were significantly higher in G1 and G2 than in G3,while the height of localized mandibular bone was smaller in G1 and G2.The length and width of localized mandibular bone were statistically smaller in patients with bilaterally impacted MM2 than those with unilaterally impacted MM2.The length and height of localized mandibular bone on unilaterally impacted side were smaller than those on the non-impacted side(P<0.05).Conclusion The crown of MM1 and MM2 were larger in patients with mesio-impacted MM2.The eruption space of MM2 was insufficient,and the space in bilaterally impacted area was narrower than in unilaterally impacted area.Besides,the presence of the mandibular third molar and gender were not significantly associated with mesial impaction of the mandibular second molar.