Video imaging analysis of movements of the condyle articular disk and its control by the lateral pterygoid muscle activity and sesory information from the periodontal ligament in rabbits

本研究的目的是分析反复电刺激咀嚼皮质区(CMA)诱导的假想咀嚼过程中兔下颌骨髁状突关节盘的运动。众所周知，刺激CMA的外侧部分会在刺激皮质的对侧诱发磨削型的有节律性的下颌运动。当我们刺激两侧的CMA时，通过盘的视频成像来比较盘在工作侧和平衡侧的运动是可能的。在麻醉兔上关节腔的顶端切除颞骨鳞状部的颧突，以拍摄视盘图像。用高速摄像机(120图像/秒)在侧位面上记录椎间盘的运动。根据切牙运动和咬肌肌电活动，将一个咀嚼周期分为9个阶段。盘在一个周期中的运动被表示为通过跟踪这些阶段的视频图像而获得的盘的一系列9条线条图。关节盘在矢状面上的运动轨迹远不是圆弧，这一点在切削型颌骨运动中尤为明显。平衡侧和工作侧的圆盘运动轨迹有很大的不同。关节盘在前后和背腹方向的运动范围约为3.5 mm。工作侧最前和最下偏斜盘的绝对位置分别比平衡侧后方1 mm和下方1 mm。关节盘最前方的时间段与所研究的同侧咬肌肌电爆发活动的时间段相吻合。结果表明，关节盘在工作侧和平衡侧的运动有很大不同。

The purpose of the present study is to analyze the movements of the articular disk of the mandibular condyle of rabbits during fictive mastication induced by repetitive electrical stimulation of the masticatory cortical area (CMA). Stimulation of the lateral portion of the CMA is well known to induce grind type of rhythmical jaw movements on the side contralateral to the cortex stimulated. It would be possible to compare the movements of the disk on the working and balancing sides by means of video imaging of the disk, when we stimulated the CMAs on both sides. To take video images of the disk, the zygomatic process of squamous part of the temporal bone, which makes the roof of upper articular cavity, was removed in anesthetized rabbits. The movements of the disk were recorded with high-speed video camera (120 images/sec ) in lateral view. One masticatory cycle was divided into 9 stages on the bases of the incisor movements and the EMG activities of the masseter. The movements of the disk in a cycle were represented as a series of 9 line drawings of the disk That were taken by tracing the video images at these stages. The trajectories of the disk movements on the sagittal plane were far from circular arc that was particularly observed in the chopper type of jaw movements. The pathway of the disk movements were widely different between on the balancing and working sides. The range of the movements of the disk was about 3.5 mm in antero-posterior and dorso-ventral directions. Absolute positions of the anterior- and inferior-most deviated disk on the working side were as much as 1 mm posterior and inferior relative to those on the balancing side, respectively. The period of the anterior-most position of the disk was coincident with the period during which the EMG burst activities of the masseter muscle ipsilateral to the condyle studied was present. It was revealed that the movements of the articular disk are widely different between on the working and balancing sides.