4種類ニッケルチタンファイルの周期疲労破折の比較研究

抄録

Abstract : Purpose : The aim of this study was to compare the cyclic fatigue resistance of four different NiTi files on rotary movement within artificial curved canals at simulated body temperature.

 Methods : An NEX NiTi file (NX group) (ISO size=#25, taper=0.06, length=25mm, n=10) and NEX Ms NiTi file (MS group) (ISO size=#25, taper=0.06, length=25mm, n=10), Vortex Blue NiTi file (VB group) (ISO size=#25, taper=0.06, length=25mm, n=10), and RE file CT NiTi file (RE group) (ISO size=#25, taper=0.06, length=25mm, n=10) were tested. All files were tested by rotary movement and the testing device was a stainless-steel artificial canal with a radius of curvature of 5mm and an angle of 45°.

 To simulate the clinical setting, testing was done with up-and-down motion at 0.5 s/4mm. All experiments were conducted at 37±1℃. All samples were subjected to rotary movement until fracture.

 The time to fracture and the lengths of broken fragments were recorded. After the cyclic fatigue resistance tests were completed, the fractured surface was inspected by a scanning electron microscope. The data was analyzed using one-way analysis of variance.

 Results : The time to fracture of the MS group, VB group and RE group were significantly longer than that of the NX group (p<0.01). The average length of broken fragments of the NX group, MS group and VB group were 4.61-4.76mm, and that of the RE group was 2.27-2.68mm. The RE group showed a significantly shorter average length of broken fragments than all other groups (p<0.01).

 Observation of the fractured cross section of the heat-treated NiTi rotary file (MS group, VB group, RE group) with a scanning electron microscope revealed numerous dimples, micro-bubbles and crater-like structures in each.

 Conclusion : The heat-treated NiTi rotary file (MS group, VB group, RE group) showed higher cyclic fatigue resistance than the NEX NiTi rotary file with continuous rotational movement in a body temperature environment.