骨性Ⅰ类及Ⅱ类患者基于锥形束CT的下颌骨对称性研究

Study of symmetry of mandible in patients with skeletal Class Ⅰ and skeletal ClassⅡbased on cone-beam CT

目的通过对骨性I类与骨性Ⅱ类患者锥形束CT影像资料进行定点测量,探讨两类患者之间下颌骨对称性的差异,分析下颌骨对称性与ANB角的相关关系。方法本文为回顾性研究。纳入骨性I类及骨性I类患者各30例,采用三维测量软件对初诊拍摄的锥形束CT资料进行下颌骨标志点的标定和线距的测量,分析对比两组患者裸突、下颌升支、下颌角、下颌体部的相关指标。结果组内对比:骨性I类组中双侧突最后点到矢状面的距离为[左侧:(52.76±2.47)mm,右侧:(53.95±2.21)mm,P=0.004]、突最侧点到矢状面的距离为[左侧:(59.40±3.31)mm,右侧:(60.79±3.37)mm,P=0.013]、乙状切迹点到矢状面的距离为[左侧:(47.88±2.18)mm,右侧:(48.84±2.54)mm,P=0.012]、喙突点到矢状面的距离为[左侧:(46.59±2.49)mm,右侧:(47.28±2.54)mm,P=0.043]和下颌升支长度[左侧:(57.00±4.50)mm,右侧:(57.97±4.96)mm,P=0.020];骨性II类组所有项目左右侧差异均无统计学意义。组间对比:测量项目突最侧点到矢状面的距离[骨性I类组:(1.39±2.88)mm,骨性Ⅱ类组:(-0.16±2.74)mm,P=0.037]、乙状切迹点到矢状面的距离[骨性I类组:(0.96±1.95)mm,骨性Ⅱ类组:(-0.15±1.97)mm,P=0.033]和下颌升支长度[骨性I类组:(0.97±2.14)mm,骨性Ⅱ类组:(-0.38±2.61)mm,P=0.033],其余项目两组间差异无统计学意义。下颌角点的不对称性与ANB角度呈负相关(r=-0.308,P=0.017)。结论骨性I类患者治疗前下颌骨的不对称较骨性Ⅱ类患者更明显,下颌角的不对称性与ANB角具有一定的相关性。

Objective To study the difference of mandibular asymmetry between patients with skeletal Class Ⅰ and ClassⅡand to analyze the correlation between mandibular asymmetry and ANB angle based on cone beam CT measurements.Methods_This is a retrospective study.Thirty patients with skeletal Class I and thirty patients with skeletal ClassⅡwere included,and the cone beam CT data was collected at patients'initial visit.We used 3D measuring software to determine the mandibular anatomic landmarks and calculate the linear distance,and to analyze and compare the measurements of condyle,mandibular ramus,mandibular angle and mandibular body of patients in two groups.Results Intra-group comparison:in skeletal Class Ⅰgroup,bilateral measurements of the distance between the most posterior point of the condyle to midsagittal plane[left side:(52.76±2.47)mm,right side:(53.95±2.21)mm,P=0.004],the distance between the outer lateral point of the condyle to midsagittal plane[left side:(59.40±3.31)mm,right side:(60.79±3.37)mm,P=0.013],the distance between sigmoid notch point to midsagittal plane[left side:(47.88±2.18)mm,right side:(48.84±2.54)mm,P=0.012],the distance between coronoid process point to midsagittal plane[left side:(46.59±2.49)mm,right side:(47.28±2.54)mm,P=0.043]and length of mandibular ramus[left side:(57.00±4.50)mm,right side:(57.97±4.96)mm,P=0.020];there was no significant difference between left and right side of allindices in skeletal ClassⅡgroup.Inter-group comparison:measurements of the distance between the most lateral point of condyle to midsagittal plane[skeletal Class.Ⅰ group:(1.39±2.88)mm,skeletal ClassⅡgroup:(-0.16±2.74)mm,P=0.037],the distance between sigmoid notch point to midsagital plane[skeletal Class Ⅰ group:(0.96±1.95)mm,skeletal Class Ⅱ group:(0.15±1.97)mm,P=0.033] and length of mandibular ramus[skeletal Class Ⅰ group:(0.97±2.14)mm,skeletal Class Ⅱ group:(-0.38±2.61)mm,P=0.033].There was no significant difference between skeletal Class I group and ClassⅡgroup of rest measurements.The asymmetry of Gonion point was negatively correlated with the ANB angle(r=-0.308,P=0.017).ConclusionsThe asymmetry of mandible in patients with skeletal ClassⅡwas more obvious than that in patients with skeletal Class Ⅱ before treatment,and the asymmetry of mandibular angle was correlated with the ANB angle.