上中切牙牙冠矢状向正畸安全移动范围函数研究

Study of the function of safe range of sagittal orthodontic movement of the crowns of upper central incisors

目的利用影像学资料拟合上中切牙牙冠矢状向正畸安全移动范围函数。方法以眶耳平面(FH平面)为x轴,垂直于FH平面为y轴,治疗前上中切牙切缘点为原点建立坐标系。根据上中切牙平移和旋转2种形式在坐标轴中描绘其正畸移动轨迹,以根颈1/3外侧缘触及骨皮质为平移界限,以根颈1/3为中心进行旋转的∠U1-FH(上中切牙长轴与眶耳平面相交的下内角)在105.5~116.5°范围内为旋转界限,构建上中切牙牙冠矢状向正畸安全移动范围函数,并采用Matlab设计函数表达。选取2020年9月至2021年9月就诊于山西医科大学第五临床医学院口腔正畸科的成人患者30例,通过函数计算上中切牙安全移动距离,再结合Downs分析法确定目标移动量。分析患者治疗后上中切牙的实际移动量及倾斜度变化,以及是否发生牙根吸收、骨开窗及骨开裂等并发症。结果根据治疗前的∠U1-FH,分别拟合了105.5°<∠U1-FH<116.5°、∠U1-FH≥116.5°和∠U1-FH≤105.5°3种条件下的内收运动函数和外展运动函数,通过治疗前∠U1-FH、上中切牙1/3根长与冠长之和、颊侧和腭侧牙槽骨厚度的测量可计算得出相应的内收量或外展量。结合Downs分析法进行正畸治疗后,所有患者的实际移动量均在函数计算的安全移动范围内,上中切牙牙根均位于牙槽骨内、未触及骨皮质,∠U1-FH在105.5~116.5°范围内,无牙根吸收、骨开窗及骨开裂等并发症发生。结论上中切牙牙冠矢状向正畸安全移动范围函数与Downs分析法结合使用设计的治疗方案具有良好的治疗效果,可为正畸临床医生提供帮助。

Objective To fit a sagittal orthodontically safe range of movement function for the crowns of the upper central incisors using imaging data.Methods The coordinate system was established with the orbital-ear plane(FH plane)as the x-axis,perpendicular to the FH plane as the y-axis,and the point of the incisal edge of the upper central incisor before treatment as the origin.The orthodontic movement trajectory of the upper central incisor was depicted in the coordinate axes based on translation and rotation of upper central incisor,with the lateral edge of the root neck 1/3 touching the bone cortex as the translation limit and the∠U1-FH(the lower inner angle of the intersection of the long axis of the upper central incisor with the orbital ear plane)in the range of 105.5-116.5°as the rotation limit,and the function of safe range of sagittal orthodontic movement of the crown of the upper central incisor was constructed and Matlab was used to design the function expression.Thirty adult patients visiting the Department of Orthodontics,the Fifth Clinical School of Shanxi Medical University from September 2020 to September 2021 were selected to calculate the safe movement distance of upper central incisors by function,and through combination with Downs analysis,the target movement was determined.Results Based on the pre-treatment∠U1-FH,the inward and outward movement functions were fitted for 105.5°<∠U1-FH<116.5°,∠U1-FH≥116.5°and∠U1-FH≤105.5°,respectively.The corresponding inward and outward movements were calculated by measuring∠U1-FH,the sum of root length 1/3 and crown length of the upper central incisor,palatal alveolar bone thickness,and buccal alveolar bone thickness before treatment.After the orthodontic treatment combined with Downs analysis,the actual movement of all patients was within the safe movement range calculated by the function,and the roots of the upper central incisors were located in the alveolar bone without touching the bone cortex,and the∠U1-FH was within the range of 105.5-116.5°.No complications such as root resorption,bone opening or bone cracking occurred.Conclusion The function of safe range of sagittal orthodontic movement of upper central incisor crown in combination with Downs analysis can be used to design a treatment plan,which has good therapeutic results and can be helpful for clinical orthodontists.