Evaluation of the Dimensional Changes in the Mandible, Condyles, and the Temporomandibular Joint Following Skeletal Class III Treatment with Chin Cup and Bonded Maxillary Bite Block Using Low-Dose Computed Tomography: A Single-center, Randomized Controlled Trial

Linear and angular measurements A new template was created from the Measure and Analyze tool of Mimics™, which was used to define the anatomical landmarks and planes and produce the desired measurements. Ikeda and Kawamura suggested that the condylar and glenoid fossa landmarks were made on the corrected sagittal view. After identifying the landmarks, the software automatically calculated the distances and the angles. Then, the data was exported in .cvs format. 3D mandibular regional superimposition and comparison analysis: The paired resulting reconstructed mandibular models were exported to 3-Matic software (3-matic13.0, Materialise NV, Leuven, Belgium), and their surfaces were warped using the Warp tool of Mimics™. Initially, The T1 and T2 3D volumes were superimposed manually by approximating similar anatomical regions of the mandible using Interactive Translate and Rotate tools of the software, followed by automatic global registration in 3-Matic software. The superimposition was repeated three times to enhance accuracy and reproducibility. The point-based analysis was performed to assess the changes in 3D mandibular models between T1 and T2, and a color map was produced to assess the mandibular shape changes. The threshold was set at 2 mm: green areas indicated differences within 2 mm (between −2 and 2 mm), red surfaces indicated positive values displacement more than 2 mm, and blue surfaces indicated negative values displacement greater than −2 mm between two 3D models. Quantitative changes were done by reporting the mean, minimum, and maximum values of part analyses on a spreadsheet and used for comparative analyses.

线性与角度测量：借助Mimics™软件的Measure and Analyze工具创建新模板，该模板用于定义解剖标志点与解剖平面，并完成预设测量操作。池田与川村提出，髁突与关节盂窝的标志点需在校正后的矢状位视图上确定。确定标志点后，软件将自动计算距离与角度值，随后将数据以.csv格式导出。
三维下颌骨区域配准与对比分析：将成对生成的重建下颌骨模型导出至3-Matic软件（3-matic13.0，Materialise NV，比利时鲁汶），并通过Mimics™的Warp工具对模型表面进行变形处理。首先，借助软件的交互式平移与旋转工具，通过匹配下颌骨相似解剖区域的方式，手动完成T1与T2三维容积的配准，随后在3-Matic软件中执行全局自动配准。为提升配准的准确性与可重复性，该配准操作重复执行三次。通过基于点的分析方法评估T1与T2时间点的三维下颌骨模型变化，并生成彩色映射图以分析下颌骨形态改变。将阈值设置为2 mm：绿色区域代表两个三维模型间差异在2 mm以内（即-2 mm至2 mm之间），红色表面代表位移值大于2 mm的正向位移区域，蓝色表面代表位移值小于-2 mm的负向位移区域。通过在电子表格中记录分项分析的均值、最小值与最大值来完成量化变化分析，并用于后续对比研究。