Al Rafee Mohammed A, Nagy William W, Fournelle Raymond A, Dhuru Virendra B, Tzenakis George K, Pechous Charles E
School of Dentistry and College of Engineering, Marquette University, Milwaukee, WI 53201-6516, USA.
J Prosthet Dent. 2002 Aug;88(2):176-82. doi: 10.1067/mpr.2002.127652.
Repeated torque may alter the mechanical properties and fracture resistance of certain prosthetic retaining screws.
This study evaluated the effect of repeated torque and salivary contamination on the ultimate tensile strength of one type of slotted gold prosthetic retaining screw.
Forty-five slotted gold prosthetic screws from the same manufacturer (Implant Innovations) were divided randomly into 9 groups of 5 screws each, with group 0X being an unused control. Groups 1XL, 5XL, 10XL, and 20XL were lubricated with human saliva, tightened to 10 Ncm, and removed 1, 5, 10, and 20 times, respectively. This procedure was performed in an unused stack of implant components consisting of an implant, an abutment cylinder and screw, and a gold cylinder. Groups 1XN, 5XN, 10XN, and 20XN were not lubricated. A custom load cell, load frame, and strain gauge torque wrench with associated electronics were used to apply torque; ultimate tensile strength was measured on a universal testing machine. Fracture load values were analyzed against torque cycles with 1-way analysis of variance and a Tukey test (P<.05). Differences between the 2 conditions (lubricated and nonlubricated) were characterized with Student's t test (P<.05).
Mean fracture load values ranged from 97.6 +/- 2.2 kg (group 0X) to 102.0 +/- 2.1 kg (group 5XN). Analysis of variance and Tukey's test revealed no significant differences between the lubricated and nonlubricated conditions for all groups and no significant reduction of tensile strength. For 2 of the nonlubricated groups, 5XN and 20XN, a significant increase in fracture load values was recorded (P=.02 and P=.03, respectively).
Within the limitations of this study, the results suggest that the slotted gold prosthetic screw tested can be tightened and removed up to 20 times without any effect on its ultimate tensile strength. The use of human saliva as a lubricant during torquing also had no apparent effect on ultimate tensile strength.
反复施加扭矩可能会改变某些修复体固位螺钉的机械性能和抗断裂能力。
本研究评估反复施加扭矩和唾液污染对一种开槽金质修复体固位螺钉极限抗拉强度的影响。
从同一制造商（种植体创新公司）获取45枚开槽金质修复体螺钉，随机分为9组，每组5枚螺钉，0X组为未使用的对照组。1XL、5XL、10XL和20XL组用人体唾液润滑，拧紧至10 Ncm，并分别拆卸1次、5次、10次和20次。该操作在由种植体、基台圆柱体和螺钉以及金质圆柱体组成的未使用的种植体组件堆中进行。1XN、5XN、10XN和20XN组不进行润滑。使用定制的测力传感器、加载框架和带有相关电子设备的应变片扭矩扳手施加扭矩；在万能试验机上测量极限抗拉强度。采用单向方差分析和Tukey检验（P<0.05）对断裂载荷值与扭矩循环次数进行分析。用Student t检验（P<0.05）对两种情况（润滑和未润滑）之间的差异进行表征。
平均断裂载荷值范围为97.6±2.2 kg（0X组）至102.0±2.1 kg（5XN组）。方差分析和Tukey检验显示，所有组在润滑和未润滑条件之间均无显著差异，且抗拉强度无显著降低。对于2个未润滑组，5XN和20XN，记录到断裂载荷值显著增加（分别为P = 0.02和P = 0.03）。
在本研究的局限性范围内，结果表明所测试的开槽金质修复体螺钉可以拧紧和拆卸多达20次，而对其极限抗拉强度没有任何影响。在施加扭矩过程中使用人体唾液作为润滑剂对极限抗拉强度也没有明显影响。
