金屬玻璃薄膜技術於鎳鈦旋轉器械表面改質之應用: 斷裂機轉及切削效率之分析

Application of Thin Film Metallic Glasses on Surface Modification of Nickel Titanium Rotary Instruments: Analysis of Fracture Mechanism and Cutting Efficiency

紀智文(Chi-Wen Chi)

指導教授 ： 林俊彬

國立臺灣大學/醫學院/臨床牙醫學研究所/博士(2016年)

https://doi.org/10.6342/NTU201602692

摘要

根管治療是牙科治療當中相當重要的一環，主要目的為移除發炎感染組織以及病原體，藉由良好的根管修形以加強根管內機械性與化學性清潔。列用傳統不銹鋼根管銼進行彎曲鈣化根管修形容易生根管偏移與破孔等醫源性併發症，而降低根管治療成功率。鎳鈦金屬合金於根管銼器械的應用，藉其超彈性與形狀記憶之性質大幅改變傳統根管修形技術。然而，鎳鈦器械仍有許多問題亟待解決，其中最主要的是器械斷裂以及切削效率不彰的問題。近些年相關之研究陸續提出，藉由器械幾何形狀、合金改質等著手，但仍無法克服器械斷裂的困擾。因此，發展器械處理技術以提升器械抗斷裂能力與切削能力是具有臨床高度意義的研究方向，同時深入探討器械切削影響機轉與斷裂機制亦是改善器械臨床表現之重要研究議題。因此本篇研究分成三個章節來探討：第一章主要是探討金屬玻璃薄膜在不同濺鍍參數下之組成與機械性質表現，搭配電化學特性測試與生物相容性試驗，找尋最適合的金屬玻璃薄膜濺鍍參數以應用於臨床器械物中。第二章則是將金屬玻璃薄膜濺鍍於鎳鈦旋轉器械上，利用不同的濺鍍厚度，以探討金屬玻璃濺鍍技術對器械本身之影響以及探討器械切削之影響機轉。第三章則著重在金屬玻璃濺鍍技術對器械疲勞斷裂與扭轉斷裂之系列性研究，利用掃描式電子顯微鏡觀察每個斷裂面之破壞型態與個別斷裂特徵。總結本實驗之結果，本實驗採用的Ti-Zr-B金屬玻璃薄膜在硼比例提升可達到較緻密的金屬玻璃薄膜，且可有較佳的抗腐蝕能力。在鎳鈦旋轉器械的應用部分，鍍膜較厚的器械呈現較平順之器械表面特性，並可達到最佳的切削效率與抗疲勞斷裂的能力；同時結果也顯示金屬玻璃濺鍍技術並不會影響到鎳鈦器械本身的超彈性特質。進一步探究鎳鈦旋轉器械疲勞斷裂的機制，可以得到在整體疲勞壽命當中，金屬玻璃薄膜主要改變了器械的表面性質也提高器械抵抗斷裂起始的能力。總結來說，Ti-Zr-B金屬玻璃薄膜技術是一項令人滿意的表面改質技術，可藉由改善器械表面特徵而提高其臨床表現。

關鍵字

鎳鈦旋轉器械 ； 金屬玻璃薄膜技術 ； 切削效率測試 ； 疲勞斷裂機制 ； 扭轉斷裂機制

並列摘要

Endodontic treatment is a crucial and significant procedure of dental treatments. The primary purpose of endodontic treatment is to remove inflamed tissue and infectious pathogens. Proper canal shaping could facilitate intracanal mechanical debridement and chemical cleaning. However, the curved canals would be deviated and perforated with the stainless steel files and the prognosis would be poor. In these decades, the philosophy of root canal shaping have improved with NiTi alloy due to its super-elastic and shape memory properties. However, there were still many issues of Ni-Ti instruments need to be improved. Unpredictable separated instrument and insufficient cutting ability were the major limitations of NiTi rotary instruments. In recent years, relevant studies have proposed to resolve these problems with instrument geometry and alloy modification etc., but the problems have not been improved. Hence, for enhancing the abilities of cutting and fracture resistance of instruments, development of instruments processing is a clinically valuable research topic. In the meantime, the mechanisms of cutting ability and fracture patterns are also important research agendas of improving clinical performance of instruments. Therefore, this research was divided into three chapters. Chapter I was focused on the composition and performance of mechanical properties of thin film metallic glass under different parameters of sputtering. According to results of mechanical properties, electrochemical characteristics and biocompatibility, it was meant to find the most suitable parameters of thin film metallic glass to apply on clinical instruments. Chapter II was utilizing different thickness of thin film metallic glass on Ni-Ti rotary instruments to explore the mechanism of cutting ability. Chapter III was focusing on mechanisms of torsional and fatigue fracture of NiTi instruments treated with Ti-Zr-B thin film metallic glass. To summarize the results of this experiment, Ti-Zr-B thin film metallic glass could be denser and would have better corrosion resistance when the content of Boron increased. As for the application of Ni-Ti rotary instruments, the ones with thicker coating appeared to have relatively smooth morphologies on instruments surface and achieved optimal cutting efficiency and resistance to fatigue fracture. Meanwhile, the results showed that metallic glass sputtering techniques would not affect the nature of super-elastic of the instrument itself. Further exploring the mechanism of fatigue fracture of Ni-Ti rotary instruments, it was found that, among the overall fatigue life, thin film metallic glass mainly changed the surface features of the instrument and improved its resistance of fracture initiation ability. In summary, the technique of Ti-Zr-B metallic glass thin film is a satisfied surface modification for improving surface features of an instrument to advance its clinical performance.

並列關鍵字

Ni-Ti rotary instruments ； metallic glass thin film techniques ； cutting efficiency test ； mechanism of fatigue fracture ； torsional fracture

參考文獻

蔡淙宇 (2010). 熱處理於鎳鈦旋轉器械切削效率影響(碩士論文). 台北, 國立台灣大學機械工程研究所

林正程 (2009).鎳鈦旋轉器械切削效率之研究 (碩士論文). 台北, 國立台灣大學機械工程研究所

張棋閔 (2008).牙科鎳鈦旋轉器械之疲勞與切削性質評估 (碩士論文). 台北, 國立台灣大學機械工程研究所

Alapati, S. B., W. A. Brantley, T. A. Svec, J. M. Powers, J. M. Nusstein and G. S. Daehn (2004). "Proposed role of embedded dentin chips for the clinical failure of nickel-titanium rotary instruments." J Endod 30(5): 339-341.

Alapati, S. B., W. A. Brantley, T. A. Svec, J. M. Powers, J. M. Nusstein and G. S. Daehn (2005). "SEM observations of nickel-titanium rotary endodontic instruments that fractured during clinical Use." J Endod 31(1): 40-43.