Smart~镍钛根管器械的扭转性能与旋转疲劳断裂行为研究

Torsional property and rotary fatigue fracture of Smart~ nickel-titanium endodontic instruments

目的:研究不同尺寸Smart镍钛合金K型锉和R型扩大针根管器械的扭转及旋转疲劳行为。方法:利用自制的扭转试验装置及模拟根管弯曲系统测定根管器械的扭转和旋转疲劳性能,光学显微镜和扫描电镜研究扭转断裂前后器械的宏观形貌和旋转疲劳断口特征。结果:K型锉和R型扩大针根管器械扭转断裂时的最大扭矩远优于ANSI/ADA第 28号标准规定。旋转疲劳断裂试验显示断裂过程中,器械外侧表面的拉应力是裂纹萌生的原因。K型和R型根管器械的疲劳断裂寿命均随尺寸和弯曲角度的增加而降低。疲劳断口形貌特征表明Smart镍钛合金根管器械具有很好的延展性,断口上有韧窝,疲劳断裂属于典型的延性断裂。结论:Smart 镍钛合金根管器械具有较佳的扭转和抗疲劳断裂特性,为该器械的进一步应用提供了试验依据。

Objective:To study the torsional property and rotary fatigue fracture of Smart K files and R reamers made of nickel-titanium alloy. Methods:The torsional property and rotary fatigue fracture behavior of Smart K files and R reamers were evaluated by means of specially-designed torsional device and simulated endodontic root canals system. The instrument surface and the rotary fatigue fractured surface were investigated by optical microscope and scanning electron microscope. Results:Compared with ANSI/ADA specification No.28, maximum torque values of Smart K and R endodontic instrument were higher. Tensile stresses on the outer surface of the endodontic instruments played a dominant role in fracture initiation during rotary fatigue fracture. The rotary numbers corresponding to rotary fatigue fracture decreased with the increase of the instrument size and curvature. Smart K and R endodontic instruments exhibited good ductility. Dimples were found on the fractured surface, and the fatigue fracture was the typical ductile fracture. Conclusion:Smartendodontic instruments have excellent torsional and rotary fatigue fracture resistance properties.