One Curve，F6 Skytaper，Protaper Next，Hyflex CMの歯内療法用ファイルの耐繰返し疲労性の比較．

Comparison of the cyclic fatigue resistance of One Curve, F6 Skytaper, Protaper Next, and Hyflex CM endodontic files.

抄録

研究目的:

従来のオーステナイト系ニッケルチタンであるOne Curve（Cワイヤー），F6 Skytaperと，熱機械処理を施したNiTiであるProtaper Next X2（Mワイヤー），Hyflex CM（CMワイヤー）の耐繰返し疲労性を比較検討した．

Objectives: This study compared the cyclic fatigue resistance of One Curve (C wire) and F6 Skytaper (conventional austenite nickel-titanium [NiTi]), and 2 instruments with thermo-mechanically treated NiTi: Protaper Next X2 (M wire) and Hyflex CM (CM wire).

材料と方法:

各群10本の新しいインスツルメント（サイズ：0.25mm，先端部3mm領域で6%のテーパー）を，曲率角60°，曲率半径5mmの回転曲げ機を用いて，室温で試験した．破断までのサイクル数を記録した．破断した器具の長さを測定した．各断片の破断面は走査型電子顕微鏡（SEM）で観察した．データは一元配置分散分析および Tukey 検定を用いて解析した．有意水準は0.05とした．

Materials and Methods: Ten new instruments of each group (size: 0.25 mm, 6% taper in the 3 mm tip region) were tested using a rotary bending machine with a 60° curvature angle and a 5 mm curvature radius, at room temperature. The number of cycles until fracture was recorded. The length of the fractured instruments was measured. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). The data were analyzed using one-way analysis of variance and the Tukey test. The significance level was set at 0.05.

結果:

60°では，One Curve，F6 SkytaperおよびHyflex CMはProtaper Next X2よりも有意に長い疲労寿命を示した（< 0.05）．One Curve，F6SkytaperおよびHyflex CMの繰返し疲労寿命には，統計的に有意な差は認められなかった（＞0.05）．また，各機器の破断面のSEM画像から，疲労破壊の典型的な特徴を確認することができた．

Results: At 60°, One Curve, F6 Skytaper and Hyflex CM had significantly longer fatigue lives than Protaper Next X2 ( < 0.05). No statistically significant differences were found in the cyclic fatigue lives of One Curve, F6 Skytaper, and Hyflex CM ( > 0.05). SEM images of the fracture surfaces of the different instruments showed typical features of fatigue failure.

結論:

本研究の条件下において，曲率半径5 mm，60°の条件で，One Curveの繰返し疲労寿命はF6 SkytaperおよびHyflex CMと有意差はなかった．また，Protaper Nextと比較して，これら3種の繰り返し疲労寿命は統計的に有意に長かった．

Conclusions: Within the conditions of this study, at 60° and with a 5 mm curvature radius, the cyclic fatigue life of One Curve was not significantly different from those of F6 Skytaper and Hyflex CM. The cyclic fatigue lives of these 3 instruments were statistically significantly longer than that of Protaper Next.