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Comparison of the Shaping Ability of Ni-Ti Rotary Instruments and Stainless Steel Hand Files in Simulated Curved Canals

鎳鈦旋轉器械與不銹鋼手動器械在模擬彎曲根管內之修形能力的比較

摘要


本研究的目的是比較鎳鈦旋轉器械和不銹鋼手動器械在模擬彎曲根管內之修形能力。本實驗將三十個相同具模擬彎曲根管的透明樹脂模型分成二組:一組使用ProTaper(上標 ®)鎳鈦旋轉器械,並根據廠商的操作建議採取crown-down技術作根管修形;另一組則使用K-flexofile(上標 ®)採取step-back技術作根管修形。全部模擬根管均由同一操作者執行。然後將修形前後之根管型態以電腦影像軟體擷取作重疊分析比較。結果顯示,鎳鈦旋轉器械在根管形態的建立、維持根管中間性和修形時間上相較於不銹鋼手動器械均有較佳的表現。同時藉由計算影像重疊後的距離差異,統計結果分析顯示鎳鈦旋轉器械在維持根管原始形態方面亦較另一組器械有顯著差異。實驗過程中有一旋轉器械發生斷裂和一旋轉器械有拉長的現象,不歸鋼手動器械則無任何斷裂情況發生。以掃描式電子顯微鏡觀察斷裂面,未發現任何裂紋反而觀察到一些明顯的弧形刮痕以順時針的方向出現在斷面周圍,同時伴隨有有許多類似蜂窩狀的小凹陷出現在破斷面中央部份,這些典型的特徵指明此為一扭轉過度所致之延性斷裂。因此儘管上述所提到的一些結果對鎳鈦旋轉器械相當有利,但是進一步在真實根管的研究仍有其必要性以預防器械的斷折。

並列摘要


The purpose of this study was to compare the shaping ability of nickel-titanium (NiTi) rotary instruments and stainless steel hand files. In total, 30 simulated curved canals in clear resin blocks were divided into 2 groups: one in which the crown-down instrumentation technique recommended in the ProTaper(superscript ®) training video was used, and the other instrumented with a step-back technique using K-Flexofiles(superscript ®). All canals were prepared by the same operator. Images of pre- and postoperative canals were superimposed and assessed using image analysis software. The results indicated that the Ni-Ti rotary instruments obtained better canal geometry, caused less canal transportation and required less preparation time than stainless steel hand files. By subtracting differences in superimposed images, statistical analysis showed that the Ni-Ti rotary instruments were significantly better in maintaining the original canal shapes. One instance of instrument separation and 1 of elongation were found with the Ni-Ti rotary instruments, whereas none of the hand files separated. The fractured surface of the separated instrument under scanning electron microscopic examination showed no evidence of crack initiation or striations but several prominent ground arc lines with dimpling formation were found clockwise in the center of the fracture surface. Such characteristics typically point to a ductile fracture caused by torsional overload. Despite the above-described favorable results with Ni-Ti rotary instruments, further research in human tooth canals is required to prevent instrument separation.

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