Throckmorton G S, Buschang P H, Hayasaki H, Pinto A S
Department of Orthodontics and the Center for Craniofacial Research and Diagnosis, Baylor College of Dentistry, Texas A&M University System, Dallas, TX 75246, USA.
Am J Orthod Dentofacial Orthop. 2001 Nov;120(5):521-9. doi: 10.1067/mod.2001.118626.
In a previous study, we established that young children with unilateral posterior crossbite have a longer mandibular ramus and more superiorly and posteriorly positioned condyles on the crossbite side. In this study, we evaluated chewing cycle shape and duration in 14 of the patients before treatment, and we looked for changes in cycle shape and duration 6 months after treatment with rapid palatal expansion. Mandibular kinematics was recorded while chewing gum using an optoelectric recording system at 100 Hz. Subjects were asked to chew normally for 20 cycles, chew on the crossbite side only for 20 cycles, and chew on the noncrossbite side only for 20 cycles. A special computer program selected the 10 most representative cycles from each series and computed an average duration and an average maximum excursion along 3 orthogonal axes. Multilevel linear models were used to generate an 8th-order polynomial describing average cycle shape and to test for statistically significant differences in shape between the patients and the controls and between the patients before and after treatment. Before treatment, the patients chewed more slowly than did the controls. Treatment shortened their cycle duration to equal control values. Before treatment, the patients also had larger maximum excursions than did the controls and exhibited a reverse-sequence cycle shape when chewing on the crossbite side. Treatment did not alter the patients' abnormal cycle shape. These results suggest that some features of the masticatory kinematics respond to orthodontic treatment alone, but others do not.
在之前的一项研究中，我们证实单侧后牙反合的幼儿下颌升支更长，反合侧髁突的位置更靠上、靠后。在本研究中，我们评估了14名患者治疗前的咀嚼周期形状和时长，并观察了快速扩弓治疗6个月后周期形状和时长的变化。使用光电记录系统以100Hz的频率记录咀嚼口香糖时的下颌运动学数据。要求受试者正常咀嚼20个周期，仅在反合侧咀嚼20个周期，仅在非反合侧咀嚼20个周期。一个特殊的计算机程序从每个系列中选择10个最具代表性的周期，并计算平均时长以及沿3个正交轴的平均最大偏移量。使用多级线性模型生成一个描述平均周期形状的8阶多项式，并测试患者与对照组之间以及治疗前后患者之间在形状上的统计学显著差异。治疗前，患者咀嚼速度比对照组慢。治疗使他们的周期时长缩短至与对照组相同的值。治疗前，患者的最大偏移量也比对照组大，并且在反合侧咀嚼时呈现反向序列的周期形状。治疗并未改变患者异常的周期形状。这些结果表明，咀嚼运动学中的一些特征仅对正畸治疗有反应，而其他特征则不然。
