Premolar extraction in orthodontics and its effect on mandibular kinematics: Axiographic data

The purpose of this study was to test whether orthodontic premolar teeth extraction had an influence on mandibular kinematics. Forty-five orthodontically treated patients (P4ex group) with premolar teeth extraction were compared with 45 paired untreated controls (P4 group). Symmetric movements were registered in 3D for both right and left sides, using a diagnostic computerised axiograph CADIAX. We measured condyle symmetric movements, specially mandibular lateral translation during protrusion/retrusion (∆Y) and speech (SP-∆Y), and the amount of rotation (SP-G) and length of the movement during speech (SP-3D). Finally the amount of Retral stability was measure (R-ST). All the mmeasurements were taken for the right (R) and left (L) sides . We found that orthodontic extraction of first premolars might disrupt jaw kinematics by increasing the amount of lateral deviations of the tracings describing the condylar movements in 25% of the cases本研究旨在探究正畸减数拔除前磨牙是否会对下颌运动学（mandibular kinematics）产生影响。研究纳入45例接受第一前磨牙拔除矫治的正畸患者（P4ex组），并以45例配对未行拔牙矫治的对照者（P4组）作为对照。借助诊断型计算机化轴式运动描记仪CADIAX，对双侧（右侧与左侧）的对称运动开展三维记录。本研究测量了髁突（condyle）对称运动相关参数，具体包括前伸/后退运动时的下颌侧方移位量（∆Y）、语音状态下的下颌侧方移位量（SP-∆Y）、语音状态下的下颌旋转量（SP-G）以及语音运动的三维长度（SP-3D）；此外还测量了下颌后退稳定性（R-ST）。所有测量均分别针对右侧（R）与左侧（L）进行。研究结果显示，正畸拔除第一前磨牙可能会干扰下颌运动学，表现为25%的受试者髁突运动轨迹的侧方偏移量显著升高。