[Preliminary measurement and analysis of the condylar movement envelope surface parameters in healthy adults].

Objective: To measure and analyze parameters of the three-dimensional (3D) model of the condylar movement envelope surface (ES) and provide a reference for the design of the temporomandibular prosthesis. Methods: Thirty-four healthy adults aged (25.4±2.8) years were recruited from the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology as subjects. There were 9 males and 25 females, most of them were university students and others outside the university have received undergraduate education or above. Condylar movement ES were obtained using the previous method on the 3D trajectory of condyle. The simulations of condylar movement were projected according to opening movements, protrusion movements, and lateral movements respectively. The total area of the ES and the area proportions of models formed by above different mandibular movements were measured and calculated. The adults' head and maxillofacial 3D models reconstructed by cone beam CT were registered with ES in Geomagic Studio. The inner and outer poles of the condyle, the corrective sagittal axis of the ES, and the median sagittal plane (MSP) were calibrated in registration models using Geomagic Studio, and the parameters were measured as follows: the anteroposterior and medialateral diameters of the condyle, the anteroposterior diameters and the transverse diameters (anterior, middle and posterior parts) of the ES, the angles between the corrective sagittal axis of the ES and MSP (ES-MSP). Pearson correlation analysis was performed by SPSS 24.0. Results: The total area of the ES was (760±133) mm2, the opening movement part accounted for (63.3±15.2)%, the protrusion movement part accounted for (14.9±9.6)%, the lateral movement part accounted for (21.8±13.3)%. Parameter measurements were as follows: mediolateral diameters of condyle was (19.8±2.3) mm; anteroposterior diameter of the ES was (21.2±3.1) mm, the transverse diameters (anterior, middle and posterior parts) of the ES were (20.6±2.4), (20.4±2.4), (22.0±2.6) mm, respectively; the transverse diameters of the ES were about 2 mm larger than that of the condyle. The angle between the corrective sagittal axis of ES and the MSP was 6.8°±6.2°. The coefficient of variation (CV) in these parameters showed: CV of the transverse diameters (anterior, middle and posterior parts) of the ES and mediolateral diameter of the condyle were 0.98, 0.99, 0.93, respectively (P<0.001). CV of aera of ES and mediolateral diameter of the condyle was 0.64 (P=0.002). CV of aera of ES and anteroposterior diameter of ES was 0.62 (P=0.004). Conclusions: The 3D envelope surface model formed by mandibular opening movements accounted for the largest proportion of the ES. The corrective sagittal axis of the ES was at an angle to the MSP, the transverse diameters (anterior, middle and posterior parts) of the ES were approximately 2 mm larger than the mediolateral diameter of the condyle, the transverse diameters (anterior, middle and posterior parts) of the ES were highly positively correlated with the mediolateral diameter of the condyle.目的： 通过测量分析健康成人下颌髁突运动包络面三维模型参数，为人工颞下颌关节窝的设计提供参考。 方法： 2019年9月至2021年9月于北京大学口腔医学院·口腔医院口腔颌面外科招募健康成年人34名（以在校大学生为主，包括少量校外人员，均接受过大学本科及以上教育）作为受试者，年龄（25.4±2.8）岁，其中男性9名，女性25名，采用下颌髁突功能面三维运动轨迹的推算模拟方法，获得研究对象的髁突运动包络面，进而分别获取髁突在下颌开口运动、前伸运动、侧方运动时的三维形态，测量包络面总面积、髁突在下颌不同运动中形成的三维形态面积及其占总面积的百分比。将受试者锥形束CT重建的头颅模型与髁突运动包络面模型配准，在Geomagic Studio软件内测量髁突前后径和内外径，包络面前后径、横径（前、中、后）以及包络面矢状角（包络面矫正矢状轴与正中矢状面的夹角）。使用SPSS 24.0进行Pearson相关性分析。 结果： 包络面总面积为（760±133）mm2，其中髁突在下颌开口运动中形成的三维形态面积占总面积的（63.3±15.2）%，前伸运动占（14.9±9.6）%，侧方运动占（21.8±13.3）%；髁突内外径为（19.8±2.3）mm；包络面前后径为（21.2±3.1）mm，包络面横径（前、中、后）分别为（20.6±2.4）、（20.4±2.4）和（22.0±2.6）mm，包络面横径比髁突内外径增大约2 mm。包络面矢状角为6.8°±6.2°，包络面横径（前、中、后）与髁突内外径均呈高度正相关（r=0.98，P<0.001；r=0.99，P<0.001；r=0.93，P<0.001），包络面总面积与髁突内外径、包络面前后径呈中度正相关（r=0.64，P=0.002；r=0.62，P=0.004）。 结论： 髁突在下颌开口运动中形成的三维形态面积在包络面总面积中占比最大，包络面矫正矢状轴与正中矢状面呈一定角度，包络面横径比髁突内外径增大约2 mm，包络面横径（前、中、后）与髁突内外径均呈高度正相关。.