鎳鈦旋轉器械切削效率之研究

Abstract

良好的切削能力是鎳鈦旋轉器械重要評估項目之一，而提升切削效率的方式除了改變鎳鈦旋轉器械外型設計之外，也有研究針對材料作各種處理。因為超深冷處理對多種材料在耐磨性、尺寸穩定性和壽命方面都有提升的效用，因此本文對鎳鈦旋轉器械作各種溫度曲線的超深冷處理，利用本實驗室開發之切削試驗機來評估超深冷處理各參數對鎳鈦根管銼切削效率的影響，並且透過DSC和靜態彎曲實驗探討超深冷處理對鎳鈦根管銼的變化影響。結果顯示，超深冷處理對鎳鈦根管銼的切削效率有提升作用，並且以降溫速率和持溫時間兩個參數對切削效率有較明顯影響。超深冷處理也使得鎳鈦根管銼的相變化溫度改變、強度增加和最大可恢復應變降低，其中相變化溫度的改變和強度的增加也是切削效率提升的原因。 同時本文就使用原切削試驗機之經驗，探討改善之方法，設計並製造新型切削試驗機，主要為改善原有的切削試驗機會加速根管銼磨耗的缺點，並且縮小旋轉座的步近角和提升施力大小的準確性，使切削評估更為客觀且合理。

Good cutting ability is one important requirement of Ni-Ti endodontic rotary instruments. To improve cutting efficiency, there have been attempts to change shape as well as fabrication procedures. It is well known that cryogenic treatment can improve the wear-resistance, dimensional stability and usable life of tool steels. In the current work, the effect of various cryogenic treatment parameters on the cutting efficiency of Ni-Ti endodontic rotary instruments. We found that the martensitic and austenitic transition temperatures, the stiffness and the cutting efficiency of Ni-Ti endodontic rotary instruments will be affected by cryogenic treatment. Most importantly, the cutting efficiency is improved by cryogenic treatment. Furthermore, the amount of improvement depends very much on the cooling rate and the holding time. In addition to the use of an existing testing machine, this study also designed and fabricated a new cutting test machine that enabled cutting efficiency test to be more accurately controlled and carried out.