鎳鈦旋轉器械非破壞檢測之研發與表面處理之應用

Development of Nondestructive Testing and Application of Surface Treatment in Nickel Titanium Rotary Instruments

李偉明(Uei-Ming Li)

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(2007年)

https://doi.org/10.6342/NTU.2007.00768

摘要

根管治療器械由於鎳鈦金屬合金的引進，不僅成為近十年來的革命性發展，更大幅改變了傳統根管修形技術。然而，截至目前為止仍然有許多問題亟待解決，其中最被關心的就是器械斷裂和重複使用後表面鈍化的問題。雖然這些年來已有許多相關的研究被提出來，在器械出現永久形變之前的無預期斷裂仍常發生。因此，研發一套可行的非破壞完整性評估技術，同時改良器械的外部構造，提升其耐磨和切削能力，是相當值得努力的研究。本篇研究將分成三個章節來探討：第一章主要是要探討非破壞檢測技術在ProFile®根管鎳鈦旋轉器械週期性疲勞上的應用，藉由安置在能創造出四種不同方向的應變計裝置，監測器械的勁度，期能發展成為一種方便操作的非破壞檢測旋鈕系統。第二章則主要是探討鎳鈦旋轉器械經熱氮化表面處理後，在抗磨耗能力、切削效率上與耐腐蝕性方面的效果。而第三章則是藉由X光光電光譜分析儀(XPS)、示差掃描量熱儀(DSC)、顯微X光繞射分析儀(micro-XRD)等儀器，探討電漿浸潤式離子佈植技術(PIII)在根管鎳鈦旋轉器械表面處理方面的應用。總結本研究的結果顯示，裂紋起始點均在器械接近最後斷裂時發生。也就是說，假如器械的壽命主要取決於裂紋的發生，在器械最終斷裂前裂紋成長的時間是非常短暫的；並且一種針對根管鎳鈦旋轉器械的非破壞性檢測系統已經被發展出來。此外，藉由熱氮化表面處理技術，氮離子被成功導入鎳鈦旋轉器械的表面；並且控制溫度在300 ºC以下，處理過後的器械有較佳的抗磨耗能力、切削效率與耐腐蝕性。更重要的，透過PIII表面處理技術，根管鎳鈦旋轉器械的表面可以成功使用氮離子作表面電漿離子佈植，同時出現帶有淡金黃色的氮化鈦層，這在XPS分析中獲得證實。並且通過DSC的分析，PIII並不會改變根管鎳鈦旋轉器械的超彈性特質。總結來說，儘管沒有任何表面型態特徵的改變被觀察到，PIII技術用以改善根管鎳鈦旋轉器械的表面機械性質如切削能力的研究仍然是必須的，並且已經在進行中。

關鍵字

鎳鈦旋轉器械 ； 非破壞檢測 ； 熱滲氮 ； 電漿浸潤式離子佈植技術

並列摘要

In the past 10 years, the revolutionary development of incorporating nickel-titanium (Ni-Ti) into endodontic files has greatly transformed the methods of root canal instrumentation. However, there are still a lot of problems demanding solutions till now. Instruments separation and surface blunt after repeated uses are the most concerned problems among them. Although a great deal of research has been undertaken to understand the reasons for instrument fracture, unexpected fractures of previous permanent deformation still occurred. Therefore, develop a possible nondestructive integrity assessment method for Ni-Ti rotary instrument and improve the surface character of Ni-Ti rotary instrument to increase its wear resistance and cutting ability are well worth making our efforts. This study was divided into three chapters: Chapter 1 was dedicated to application of nondestructive testing in cyclic fatigue of endodontic Ni-Ti rotary instruments. Utilizing a device to monitor its stiffness by using two strain gages in four different directions, we could develop a convenient nondestructive turn-key system that allows assessment of the integrity of Ni-Ti instruments in the clinic. The specific aim of chapter 2 was to investigate the effects of thermal nitriding surface treatment of Ni-Ti instruments on the wear resistance, cutting efficiency and anticorrosion. Chapter 3 focused on the application of plasma immersion ion implantation (PIII) for the surface treatment of Ni-Ti rotary instruments by utilizing x-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC) and micro x-ray diffraction (micro-XRD). Through these tests, we found that crack initiation occurred near final fracture. That means, if the life span of the instrument mainly depends on crack initiation and the duration of crack growth before final fracture is very short. A possible nondestructive integrity assessment method for Ni-Ti rotary instrument was developed. In addition, the nitrogen ions were successfully introduced onto the surface of Ni-Ti instruments by using thermal nitriding. Post-nitrided files at a controlled temperature of < 300 ºC showed increased wear resistance, cutting efficiency as well as corrosion resistance. More importantly, the surfaces of Ni-Ti instruments could be successfully modified by the nitrogen PIII and a light golden TiN layer was present under XPS analysis. The PIII technique did not alter the superelastic character of the Ni-Ti instruments by way of DSC analysis. In conclusion, although no surface morphological changes were evident, studies of the effects of cutting on PIII instrument surfaces are needed and are in progress.

並列關鍵字

Nickel-titanium (Ni-Ti) rotary instrument ； Nondestructive testing ； Thermal nitriding ； Plasma immersion ion implantation (PIII)

參考文獻

Li UM, Chiang YC, Chang WH, Lu CM, Chen YC, Lai TM, Lin CP (2006). Study of the effects of thermal nitriding surface modification of nickel titanium rotary instruments on the wear resistance and cutting efficiency. Journal of Dental Science 1: 53-58.

蕭琮仁 (2004). 牙齒根管治療之鎳鈦旋轉器械完整性檢測與評估 (碩士論文). 台北, 國立台灣大學機械工程學研究所。

Alapati SB, Brantley WA, Svec TA, Powers JM, Mitchell JC, Alapati SB, et al. (2003). Scanning electron microscope observations of new and used nickel-titanium rotary files. Journal of Endodontics 29(10):667-9.

Alapati SB, Brantley WA, Svec TA, Powers JM, Nusstein JM, Daehn GS, et al. (2004). Proposed role of embedded dentin chips for the clinical failure of nickel-titanium rotary instruments. Journal of Endodontics 30(5):339-41.

Alapati SB, Brantley WA, Svec TA, Powers JM, Nusstein JM, Daehn GS, et al. (2005). SEM observations of nickel-titanium rotary endodontic instruments that fractured during clinical Use. Journal of Endodontics 31(1):40-3.