A study on occlusion and periodontium using high precision displacement detector

我们开发了四种不同类型的运动检测器来研究咬合和牙周组织的特性。这些运动探测器利用磁场和测量六个自由度的运动。第一个运动探测器由六个边长为1800 mm的方形线圈组成。在立方磁场中心区域，测量精度达到10μm量级。由于该装置具有环绕人体的大磁场，可用于夜间磨牙时下颌运动的测量。第二个运动检测器采用磁性合金作为初级线圈的磁芯。由于该装置体积较小，操作方便，可用于日常牙科诊所。第三个运动检测器具有更高的精度，可以测量牙齿在咬合过程中的轻微移动。该装置由六个直径为1000mm的圆形线圈组成，在磁场中心区的测量精度为平移1.3 μm，旋转0.00017 °。用该装置对右侧上颌第一前磨牙和下颌运动进行同步测量。咬合接触对牙齿移动有很大的影响，在某些情况下，牙齿移动的旋转中心被发现在牙齿附近。最后一个运动检测器测量单自由度的移动，但具有极高的精度，可以用咬合力来评估牙齿变形。用该装置测量上颌尖牙和第一前磨牙颊面垂直长度。这些牙齿的颊面缩短与颊尖加载和扩大与腭尖加载。

We developed four different types of motion detector to study occlusion and periodontal tissue properties. These motion detector utilizes magnetic field and measure movement in six degrees of freedom.The first motion detector consisted in six square coils 1800 mm on a side. The accuracy of the measurement is the level of 10μm at the central area of cubic magnetic field. Since this device possesses large magnetic field that surround whole human body, the system can be applied for the measurement of the jaw movement during nocturnal bruxsim.The second motion detector used magnetic alloy for the core of the primary coils. Since this device has relatively small size, the system can handle easily and may used in daily dental clinic.The third motion detector possess higher accuracy that enable to measure slight tooth movement during occlusion. This device consisted in six round coils 1000mm in diameter and the accuracy of the measurement is the level of 1.3 μm for translation and 0.00017 degrees for rotation at the central area of magnetic field. The simultaneous measurement of right side upper first premolar and jaw movement was performed with this device. Occlusal contacts were very influential for tooth movement and the rotation centers of the tooth movement were found near teeth in some cases.The last motion detector measures movement in one degree of freedom but possesses extremely high accuracy that enable to evaluate tooth deformation with occlusal force. Vertical length of buccal surface of upper canine and first premolar was measured with this device. Buccal surfaces of these teeth were shortened with buccal cusp loading and expanded with palatal cusp loading.