Development of the tooth preparation system with low noize and facility to support die preparation

传统的牙科飞机机头会发出令人不舒服的高频噪声，成为阻碍牙科治疗的因素之一。噪声来源于高转速的涡轮，如300,000-500,000转/分。而目前，模具准备完全由牙科医生手工完成，尤其是牙科专业的学生，掌握这项技术难度很大。为了降低高频噪声，对涡轮产生的噪声进行了频谱分析，在450,000转/分转速下检测到了频率随转速增加的几组噪声，如7.5~15.0 kHz22.5 kHz。发现它们是从汽轮机头上、下间隙泄漏而产生噪声的。在模具准备过程中，装配了一种带有连杆机构的支承夹具，该支承夹具在口部有固定点。两名分别从业2年和10年以上的指导牙医使用该机构制作了上、下树脂模型磨牙，并对所制备的模具进行了锥角和轴线平行度的检测。这种机制有助于正确的准备，准备的锥角减少到约10ﾟ-14ﾟ，轴与轴之间的倾角在2ﾟ以内，标准偏差也减小了。一位没有经验的牙科学生尝试使用这种机制来训练准备，这也是有帮助的，他在技术上取得了显著的进步。

A conventional dental airturbine handpiece emits so uncomfortable high frequency noise that it is one of the hindrances for the dental treatment. The noise originates from the turbine with high revolution such as 300,000 to 500,000 rpm. While, at present, die preparation is completely carried out manually by a dentist, and it is difficult to master the technique especially for dental students. In the present study, we aimed the development of the tooth preparation system with low noise and facility to support die preparation.In order to reduce the high frequency noise, the spectrum analyzes of the noise emitted from the turbine was initially carried out, and some groups of noises which increase the frequency with the revolution was detected, for instance, noise with frequencies of 7.5 15.0 22.5kHz were detected in the 450,000 rpm. It was found that they were leaked from the upper and lower clearances in the turbine head and causes the noise. Then, shilding and adjusting in the clearance were done, and it was quite effective to reduce the noise.In the case of die preparation, a support jig with link mechanism which has fix point in the mouth was assembled. Two supervising dentists with career of two years and more than ten years respectively prepared upper and lower resin model molar teeth using this mechanism, and the taper angle and axis parallelity in the prepared die were examined. This mechanism was helpful for the correct preparation, and the prepared taper angles were reduced to about 10ﾟ-14ﾟ, and tils angle between the axs was within 2ﾟ, and their standard deviations also decreased.A student in the faculty of dentistry who has no experience attempted to train the preparation using this mechanism, and it was also helpful and he obtained marked progress in the technique.