Quantitative assessment for effects of premolar extraction upon orthodontic treatment outcomes

对于8名接受拔牙治疗的成年女性和8名接受拔牙治疗的女性，在治疗前后分别记录了她们咀嚼口香糖时的3D下颌运动。已知物理性质的标准化口香糖被用于测试食品。具体来说，我们分析了正畸治疗对颌骨运动平稳性的影响。利用归一化的抖动代价和最小抖动模型的仿真结果估计了下颚运动轨迹的平稳性。结果显示，术后两组患者的下颌运动平稳性均有显著改善。拔除前磨牙后患者的下颌运动平滑度与正常受试者相比无显著差异。这表明，前磨牙的拔除是经常必要的边缘治疗可能有助于实现最佳的下颌运动平滑，这显然是在对照组中看到的

For eight adult females who underwent edgewise treatment with extraction and eight females who underwent the treatment with extraction of four premolars, their 3D jaw movements during gum chewing have been recorded at pre and post treatment periods. The standardized gum having known physical properties has been used for the test foods. Specifically, the analyses for the effects of orthodontic treatment on the smoothness of the jaw movement have been conducted. The smoothness of the jaw movement trajectories has been estimated by using normalized jerkcost as well as the simulation results by the minimum jerk model. The jaw movement smoothness was compared with thatdeterminedinthefemalesubjectswithacceptable goodocclusionThe present results showed significant postoperative improvement in the jaw movement smoothness in the two patient groups. As for the jaw movement smoothness for the patients treated with premolar extraction, the smoothness at the post treatment periods was not significantly different from that for the normal subjects. It is suggested that the extraction of the premolar that is often necessary for the edgewise treatment may contributes to achievement of the optimal jaw movement smoothness that is apparently seen in the control subjects