Newitter D A, Gwinnett A J, Caputo L
Am J Dent. 1989 Jun;2(3):81-5.
Dull twist drills used for pin channels have been cited as an etiology for dentinal cracks. This investigation examined the dulling phenomenon after repeatedly using twist drills. Inspection of the twist drills in the SEM for metal deformation revealed no alteration of the cutting edges but an accumulation of a smear debris was noted behind the cutting edges of the cone-shaped drill. Debris was also recorded on the land and flute spiral surfaces with morphological changes on the dentinal walls. These surfaces progressed serially from a rough surface to a smooth, plaque-like surface with fine striations oriented toward the drill rotation. The timing of the changes coincided with dentinal cracking reported by others. Dulling of twist drills in dentin can be attributed to adherence of byproducts rather than a loss of the cutting edge.
用于钉道的钝麻花钻被认为是牙本质裂纹的一个病因。本研究检查了麻花钻反复使用后的钝化现象。在扫描电子显微镜下检查麻花钻的金属变形情况，发现切削刃没有改变，但在锥形钻的切削刃后面有一层涂抹性碎屑堆积。碎屑也记录在刃带和螺旋槽表面，牙本质壁有形态变化。这些表面依次从粗糙表面发展为光滑的、斑块状表面，有朝向钻头旋转方向的细纹。这些变化的时间与其他人报告的牙本质裂纹发生时间一致。牙本质中麻花钻的钝化可归因于副产物的附着，而不是切削刃的磨损。
