臺灣博碩士論文加值系統

近年來鎳鈦旋轉器械在根管治療的應用上快速發展，但是器械斷裂的問題仍然是亟待解決的嚴肅問題，尤其當器械在彎曲的根管內旋轉時會遭受到張應力和壓應力，這兩種應力會侷限在根管彎曲的部分，進而對器械產生最具破壞性的斷裂效應。但是到目前為止，相關的研究均以靜態的方式作測試，而缺乏動態方面的研究。所以本研究的目的，主要是探討鎳鈦旋轉器械的斷裂機轉，並找出預防器械斷裂的方法，進而對臨床醫師及一般研究者提出建議。研究方向分為兩部分，首先是鎳鈦旋轉器械之斷裂圖相研究，這主要是藉著從許多醫師所蒐集來的112支ProFileâ斷折器械，記錄其號數、錐度、斷裂位置距離尖端的長度、並以掃描式電子顯微鏡觀察器械的斷裂面，來分析其斷裂的種類及原因；其次是評估在使用不同轉速和不同進出動作的長度情況下，鎳鈦旋轉器械在模擬彎曲根管的金屬塊上旋轉時的週期性疲勞，以及對如何防止鎳鈦旋轉器械的斷裂提出建議。在三種轉速下，共使用150支ProFileâ器械，並將其分成靜態組和動態組，以萬能測試機實驗直到這支器械斷裂時才停止。所獲得的全部資料是經由複回歸統計法來作分析，並且使用95﹪信賴區間。而分離器械的斷裂面則置於掃描式電子顯微鏡下作觀察。
研究結果顯示：第一部份：不論器械的號數或錐度的大小與否，器械若發生斷裂，其斷裂位置距離尖端的平均長度均在根尖三分之一處以內，約3到5 mm；並且在數量的統計上以錐度為0.04、大小為ISO25號、且工作長度為21mm者最多。以電子顯微鏡觀察斷面，發現有將近七成的器械斷裂呈現扭曲變形的型態，此為扭力過度超過彈性限度所致，而其餘的三成均有疲勞裂紋成長的圖相出現，表示該器械斷裂是因周期性疲勞所導致。第二部份：在靜態的群組中，斷裂時間的平均值與不同彎曲角度和不同的轉速均具有顯著的差異。當轉速增加或彎曲的角度增加時，斷裂時間減少。在動態的pecking motion群組中，斷裂時間的平均值與不同進出的長度和不同的轉速均具有顯著的差異。在本實驗中，無論使用何種長度的進出動作，當轉速增加時，斷裂時間減少；當進出動作的長度增加時，斷裂時間增加。另外在斷裂圈數方面，轉速並不是影響達到斷裂所需之圈數的重要因素。然而，在達到斷裂所需之圈數與不同進出的長度及不同角度之間具有顯著的差異。當進出動作的長度增加或彎角度越小時，達到斷裂所需之圈數增加。掃描式電子顯微鏡下的觀察顯示，延性斷裂是最主要的週期性疲勞失敗模式。因此，為了預防鎳鈦旋轉器械的斷裂，在整個根管製備中使用適當的轉速和連續的進出動作是值得被推薦的。

Over the years, the revolutionary development of incorporating nickel-titanium（NiTi）into endodontic files has greatly transformed the methods of root canal instrumentation. They help minimize the undesirable complications often encountered during instrumentation in fine and curved canals. Files made from this alloy are biologically acceptable, highly flexible and considerably stronger in fatigue resistance than stainless steel (SS) files. Despite its increased strength and flexibility, separation is still a concern with NiTi instruments, and they have been reported to undergo unexpected fractures. Endodontic instruments upon rotation are subjected to both tensile and compressive stress in curved canals. This stress is localized at the point of curvature. This is the most destructive mode of cyclic loading. But little scientific data have been published about the life span of Ni-Ti rotary instruments while they were located at the mode of pecking motion or static condition, and activated at different rotational speeds. The purpose of this study was to investigate the possible fracture patterns and mechanisms of nickel titanium rotary instruments, and lead to recommendations for preventing instrument separation. The specific aims of this study were as follows: the first aim is fractographic study of nickel titanium rotary instruments. One hundred and twelve fractured instrument fragments had been collected, recording their size, taper, and the length of fracture site from the tip, and were examined under scanning electron microscope（SEM）. The second aim is to evaluate the cyclic fatigue of 0.04 ProFile® nickel titanium rotary instruments operating at different rotational speeds and varied moving distances of pecking motion in the metal blocks that simulated curved canals. A total of 150 ProFile® instruments were made to rotate freely in a 75° sloped metal block at speeds of 200, 300, or 400 rpm by a contra-angle handpiece mounted on an Instron machine. The electric motor and Instron machine were activated until the instruments were broken in two different modes, static and dynamic pecking-motion. The fractured surfaces of separated instruments were examined under a scanning electron microscope. All data obtained were analyzed by a stepwise multiple regression method using a 95% confidence interval.
The results revealed that the first, no matter what instrument size or taper, all the mean length of fracture site from the tip locate between 3 mm and 5 mm. In addition, almost 70﹪ instrument separation is owing to torsional overload after exceeding their elastic limit, and the other reveals ductile fracture as the fatigue failure mode. The second, the time to failure significantly decreased as the angles of curvature or the rotational speeds increased. As the moving distances of pecking motion increased, the time as well as the numbers of cycles to fracture increased. Microscopic evaluation indicated that ductile fracture was the major cyclic failure mode. In order to prevent breakage of a NiTi rotary instrument appropriate rotational speeds and continuous pecking motion in the root canals are recommended.

謝誌------------------------------------------------------------------------------------I
目錄-----------------------------------------------------------------------------------II
表次-----------------------------------------------------------------------------------V
圖次----------------------------------------------------------------------------------VI
壹、中文摘要------------------------------------------------------------------------1
貳、英文摘要-------------------------------------------------------------------------3
參、前言-------------------------------------------------------------------------------6
肆、文獻回顧-------------------------------------------------------------------------9
一、根管治療器械的發展------------------------------------------------------9
二、鎳鈦旋轉器械的出現----------------------------------------------------11
三、根管器械斷裂的測試標準----------------------------------------------12
四、鎳鈦旋轉器械的週期性疲勞------------------------------------------13
五、斷裂力學與機轉的探討------------------------------------------------14
六、根管治療器械的製造---------------------------------------------------24
七、斷裂面特徵的研究------------------------------------------------------26
伍、動機與目的--------------------------------------------------------------------29
第一部份：鎳鈦旋轉器械之斷裂圖相研究----------------------------------31
一、材料與方法---------------------------------------------------------------31
1、樣本的收集--------------------------------------------------------------31
2、樣本的處理-------------------------------------------------------------31
3、樣本的紀錄-------------------------------------------------------------32
4、掃描式電子顯微鏡的觀察-------------------------------------------32
二、結果-------------------------------------------------------------------------34
1、斷裂長度的分析--------------------------------------------------------34
2、電子顯微鏡的觀察分析----------------------------------------------34
三、討論-------------------------------------------------------------------------37
1、斷裂長度的分析--------------------------------------------------------37
2、電子顯微鏡的觀察分析-----------------------------------------------37
第二部份：鎳鈦旋轉器械的週期性疲勞研究：靜態與動態測試-------41
Pilot study：--------------------------------------------------------------------41
一、材料與方法----------------------------------------------------------------41
1、樣本的預備--------------------------------------------------------------41
2、操作方法-----------------------------------------------------------------44
二、結果與討論----------------------------------------------------------------45
Main study：--------------------------------------------------------------------46
一、材料與方法----------------------------------------------------------------46
1、樣本的預備--------------------------------------------------------------46
2、操作方法-----------------------------------------------------------------47
二、結果-------------------------------------------------------------------------50
1、達到斷裂所需的時間分析--------------------------------------------50
2、達到斷裂所需的圈數分析--------------------------------------------50
3、掃瞄式電子顯微鏡分析-----------------------------------------------51
三、討論-------------------------------------------------------------------------52
陸、結論-----------------------------------------------------------------------------55
柒、參考文獻-----------------------------------------------------------------------56
表次
表1、在轉速為400 rpm、深度為6 mm下，使用四種不同角度的金屬塊所測得之斷裂時間的平均值----------------------------------- 67
表2、在轉速為400 rpm、深度為7 mm下，使用四種不同角度的金屬塊所測得之斷裂時間的平均值----------------------------------- 67
表3、各種不同大小之器械的數目與斷裂位置距離尖端的平均長度-68
表4、各種不同錐度之器械的數目與斷裂位置距離尖端的平均長度-68
表5、各種不同長度之器械的數目與斷裂位置距離尖端的平均長度-69
表6、兩種不同斷裂型態之器械的數目與百分比-------------------------69
表7、在靜態的群組中，每個彎曲角度在三種不同轉速下所測得斷裂時間的平均值----------------------------------------------------------- 70
表8、在動態的pecking motion群組中，兩種彎曲角度在三種不同轉速下，每個進出動作的長度所測得斷裂時間的平均值---------71
表9、在靜態的群組中，每個彎曲角度在三種不同轉速下所測得斷裂圈數的平均值----------------------------------------------------------- 72
表10、在動態的pecking motion群組中，兩種彎曲角度在三種不同轉速下，每個進出動作的長度所測得斷裂圈數的平均值----73
圖次
圖1、晶格構造變化圖Martensitic transformation--------------------------74
圖2、型態記憶效果Shape memory-------------------------------------------75
圖3、晶格回彈效應Springback-----------------------------------------------76
圖4、小型器械超音波震盪器-------------------------------------------------77
圖5、測量長度器ENDO-M-BLOC------------------------------------------78
圖6、使用銀膠固定斷針於電子顯微鏡專用載台-------------------------79
圖7、掃描式電子顯微鏡Topcon ABT-60-----------------------------------80
圖8、扭力過度torsional overload --------------------------------------------81
圖9、嚴重扭曲severe distortion ----------------------------------------------82
圖10、頸部現象necking phenomenon ---------------------------------------83
圖11、塗抹層狀表面smear-like surface ------------------------------------84
圖12、臨床週期性疲勞（150 X）----------------------------------------------85
圖13、臨床週期性疲勞（1000 X）---------------------------------------------86
圖14、臨床週期性疲勞（2000 X）---------------------------------------------87
圖15、臨床週期性疲勞（5000 X）---------------------------------------------88
圖16、萬能測試機Instron 5566 ----------------------------------------------89
圖17、四種具有不同角度斜坡的金屬塊------------------------------------90
圖18、以Schneider氏法所作的四種角度修正----------------------------91
圖19、下方金屬底座夾具------------------------------------------------------92
圖20、上方彎手機夾具---------------------------------------------------------93
圖21、電動馬達TCM ENDO -------------------------------------------------94
圖22、鎳鈦旋轉器械ProFile® ------------------------------------------------95
圖23、與電腦連結之立體顯微鏡Leica -------------------------------------96
圖24、以Schneider氏法所作的角度修正----------------------------------97
圖25、實驗室週期性疲勞（200 X）-------------------------------------------98
圖26、實驗室週期性疲勞（1000 X）-----------------------------------------99
圖27、實驗室週期性疲勞（2000 X）----------------------------------------100
圖28、實驗室週期性疲勞（5000 X）----------------------------------------101

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