Department of Orthodontics and Dentofacial Orthopedics, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki, 852-8588, Japan.
Department of Orthodontics, Nagasaki University Hospital, 1-7-1 Sakamoto, Nagasaki, 852-8588, Japan.
Biomed Eng Online. 2019 May 16;18(1):59. doi: 10.1186/s12938-019-0672-z.
Mastication is one of the most fundamental functions for the conservation of life. The demand for devices for evaluating stomatognathic function, for instance, recording mandibular movements or masticatory muscle activities using animal models, has been increasing in recent years to elucidate neuromuscular control mechanisms of mastication and to investigate the etiology of oral motor disorders. To identify the fundamental characteristics of the jaw movements of mice, we developed a new device that reconstructs the three-dimensional (3D) movement trajectories on an arbitrary point on the mandible during mastication.
First, jaw movements with six degrees of freedom were measured using a motion capture system comprising two high-speed cameras and four reflective markers. Second, a 3D model of the mandible including the markers was created from micro-computed tomography images. Then, the jaw movement trajectory on the certain anatomical point was reproduced by integrating the kinematic data of the jaw movements with the geometric data of the mandible.
The 3D movements at any points on the mandible, such as the condyle, molar, and incisor during mastication, could be calculated and visualized with an accuracy > 0.041 mm in 3D space. The masticatory cycle was found to be clearly divided into three phases, namely, the opening, closing, and occlusal phases in mice.
The proposed system can reproduce and visualize the movements of internal anatomical points such as condylar points precisely by combining kinematic data with geometric data. The findings obtained from this system could facilitate our understanding of the pathogenesis of eating disorders or other oral motor disorders when we could compare the parameters of stomatognathic function of normal mice and those of genetically modified mice with oral behavioral dysfunctions.
咀嚼是维持生命的最基本功能之一。近年来，人们对评估咀嚼功能的设备的需求不断增加，例如，使用动物模型记录下颌运动或咀嚼肌活动，以阐明咀嚼的神经肌肉控制机制，并研究口腔运动障碍的病因。为了确定小鼠下颌运动的基本特征，我们开发了一种新设备，可以在咀嚼过程中重建下颌任意点的三维（3D）运动轨迹。
首先，使用由两个高速摄像机和四个反射标记组成的运动捕捉系统测量具有六个自由度的下颌运动。其次，从微计算机断层扫描图像创建包括标记的下颌骨 3D 模型。然后，通过将下颌运动的运动学数据与下颌骨的几何数据集成，再现特定解剖学点上的下颌运动轨迹。
可以计算和可视化咀嚼过程中下颌骨上任意点（如髁突、磨牙和切牙）的 3D 运动，其精度在 3D 空间中>0.041mm。发现咀嚼周期可明显分为三个阶段，即开口、闭合和咬合阶段。
该系统可以通过将运动学数据与几何数据相结合，精确地再现和可视化内部解剖点（如髁突点）的运动。当我们能够比较正常小鼠和具有口腔行为功能障碍的遗传修饰小鼠的咀嚼功能参数时，该系统获得的结果可以促进我们对进食障碍或其他口腔运动障碍发病机制的理解。
