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

传统的牙科空气涡轮手机会发出令人不适的高频噪音，成为牙科治疗的障碍之一。噪声来自于30万~ 50万转/分的高转速涡轮。而目前模具的制备完全是由牙医手工完成的，特别是牙科专业的学生很难掌握。在本研究中，我们的目标是开发低噪音和方便的牙齿准备系统，以支持模具准备。为了降低涡轮的高频噪声，初步对涡轮发出的噪声进行了频谱分析，检测到一些随转速增加而频率增加的噪声组，如在45万转时检测到频率为7.5 - 15.0 - 22.5kHz的噪声。发现它们是从水轮机头的上下间隙泄漏的，并引起噪音。在此基础上，对间隙进行屏蔽和调整，取得了较好的降噪效果。在模具准备的情况下，装配了一种带有连杆机构的支撑夹具，该机构的定点在口部。2名执业2年以上和从业10年以上的督导牙医分别使用该机构制备上、下树脂模型磨牙，并对制备模具的锥度角和轴线平行度进行了检测。该机制有助于正确制备，制备的锥度角降至10 14左右，轴间夹角降至2以内，其标准偏差也有所降低。一个没有经验的牙科学院的学生尝试用这种机制来训练准备，也很有帮助，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.