頻率與溫度效應對鎳鈦根管旋轉器械疲勞壽命的影響

A Critical Analysis of Frequency and Temperature Effect on the Fatigue Life of Rotary Endodontic Instrument

劉昭沅(Chau-Yuan Liu)

指導教授 ： 單秋成

國立臺灣大學/工學院/機械工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.03374

摘要

鎳鈦旋轉器械近年被大量應用在進行牙科根管治療，臨床上在牙髓腔內承受張應力(tension)和壓應力(compression)的循環應力作用下，往往會導致無預警疲勞破壞的發生。有研究者認為使用較低轉速可以有較佳的疲勞壽命，但也有人認為轉速與疲勞壽命無關，這些研究都忽略了不同轉速時的溫度效應，本文分別探討轉速與溫度對鎳鈦旋轉器械疲勞壽命的影響，發現溫度對疲勞壽命有十分重要的影響，其影響機制與鎳鈦材料中麻田散鐵(Martensite)與沃斯田鐵(Austenite)相變態有密切關係，而轉速效應很可能是影響了器械的溫度，從而改變其疲勞壽命，此結果也顯示如臨床上能有效降低器械的溫度，應可大幅增加其抗疲勞能力，減低意外斷裂發生的糾紛。
此外，本文也利用深冷技術(Cryogenic treatment)對鎳鈦旋轉器械進行處理，發現經深冷處理後的鎳鈦旋轉器械，其疲勞壽命較未經處理的提升約10%，因此臨床上若能使用經深冷處理後的鎳鈦旋轉器械且有效地降低器械的溫度，便能獲得最佳的疲勞壽命。

關鍵字

鎳鈦旋轉器械 ； 疲勞破壞 ； 溫度效應 ； 轉速效應 ； 深冷技術 ； 麻田散鐵 ； 沃斯田鐵

並列摘要

NiTi rotary instruments are liable to accidental fatigue failure endodontic treatment. Some proposed that the fatigue life of these rotary instruments may be improved by using a lower rotational speed during operation. However, other studies found no correlation between rotational speed and fatigue life. Temperature rise of the instrument under use was overlooked in these studies. In the current work, we investigated the effects of rotational speed as well as temperature. It was found that temperature has a large impact on the fatigue properties of the NiTi instrument. Such effect was related to the phase transformation that took place in the material. Different rotational speeds probably brought about different temperature rises, which in turn affected the fatigue life. The clinical implication is that instrument life and reliability may be greatly improved if its temperature can be kept below a certain level.
This study also investigated the effect cryogenic treatment on the fatigue properties of NiTi endodontic rotary instrument. It was found that cryogenic treatment offers 10% improvement in fatigue life. Fatigue life may be greatly enhanced if we can use this technology and control the operation temperature.

並列關鍵字

NiTi endodontic rotary instrument ； Fatigue fracture ； Temperature effect ； Frequency effect ； Cryogenic ； Martensite ； Austenite

參考文獻

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