Chen Si, Xu Tian-min, Lou Hang-di, Rong Qi-guo
Department of Orthodontics, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing 100081, China.
Zhonghua Kou Qiang Yi Xue Za Zhi. 2012 Dec;47(12):730-4. doi: 10.3760/cma.j.issn.1002-0098.2012.12.009.
To get individualized facial three-dimensional finite element (FE) model from transformation of a generic one to assist orthodontic analysis and prediction of treatment-related morphological change of facial soft tissue.
A generic three-dimensional FE model of craniofacial soft and hard tissue was constructed based on a volunteer's spiral CT data. Seven pairs of main peri-oral muscles were constructed based on a combination of CT image and anatomical method. Individualized model could be obtained through transformation of the generic model based on selection of corresponding anatomical landmarks and radial basis functions (RBF) method. Validation was analyzed through superimposition of the transformed model and cone-beam CT (CBCT) reconstruction data. Pre- and post-treatment CBCT data of two patients were collected, which were superimposed to gain the amount of anterior teeth retraction and anterior alveolar surface remodeling that could be used as boundary condition. Different values of Poisson ratio ν and Young's modulus E were tested during simulation.
Average deviation was 0.47 mm and 0.75 mm in the soft and hard tissue respectively. It could be decreased to a range of +0.29 mm and -0.21 mm after a second transformation at the lip-mouth region. The best correspondence between simulation and post-treatment result was found with elastic properties of soft tissues defined as follows. Poisson ratio ν for skin, muscle and fat being set as 0.45 while Young's modulus being set as 90.0 kPa, 6.2 kPa and 2.0 kPa respectively.
Individualized three-dimensional facial FE model could be obtained through mathematical model transformation. With boundary condition defined according to treatment plan such FE model could be used to analyze the effect of orthodontic treatment on facial soft tissue.
通过对通用面部三维有限元模型进行变换，获取个性化面部三维有限元模型，以辅助正畸分析并预测治疗相关的面部软组织形态变化。
基于一名志愿者的螺旋CT数据构建颅面部软硬组织的通用三维有限元模型。结合CT图像和解剖学方法构建七对主要口周肌肉。通过基于相应解剖标志点的选择和径向基函数（RBF）方法对通用模型进行变换，可获得个性化模型。通过将变换后的模型与锥形束CT（CBCT）重建数据叠加来分析验证。收集两名患者治疗前和治疗后的CBCT数据，将其叠加以获得前牙内收量和前牙槽表面重塑量，用作边界条件。在模拟过程中测试不同的泊松比ν和杨氏模量E值。
软组织和硬组织的平均偏差分别为0.47mm和0.75mm。在唇口区域进行二次变换后，偏差可降至+0.29mm至 -0.21mm范围内。当软组织弹性特性定义如下时，模拟结果与治疗后结果的对应性最佳。皮肤、肌肉和脂肪的泊松比ν分别设为0.45，杨氏模量分别设为90.0kPa、6.2kPa和2.0kPa。
通过数学模型变换可获得个性化的面部三维有限元模型。根据治疗计划定义边界条件后，该有限元模型可用于分析正畸治疗对面部软组织的影响。
