Kazemi Mahmood, Rohanian Ahmad, Monzavi Abbas, Nazari Mohammad Sadegh
Assistant Professor, Department of Prosthodontics, Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
J Dent (Tehran). 2013 Mar;10(2):112-8. Epub 2013 Mar 31.
Accurate delivery of torque to implant screws is critical to generate ideal preload in the screw joint and to offer protection against screw loosening. Mechanical torque-limiting devices (MTLDs) are available for this reason. In this study, the accuracy of one type of friction-style and two types of spring-style MTLDs at baseline, following fatigue conditions and sterilization processes were determined.
Five unused MTLDs were selected from each of Straumann (ITI), Astra TECH and CWM systems. To measure the output of each MTLD, a digital torque gauge with a 3-jaw chuck was used to hold the driver. Force was applied to the MTLDs until either the friction styles released at a pre-calibrated torque value or the spring styles flexed to a pre-calibrated limit (target torque value). The peak torque value was recorded and the procedure was repeated 5 times for each MTLD. Then MTLDs were subjected to fatigue conditions at 500 and 1000 times and steam sterilization processes at 50 and 100 times and the peak torque value was recorded again at each stage.
Adjusted difference between measured torque values and target torque values differed significantly between stages for all 3 systems. Adjusted difference did not differ significantly between systems at all stages, but differed significantly between two different styles at baseline and 500 times fatigue stages.
Straumann (ITI) devices differed minimally from target torque values at all stages. MTLDs with Spring-style were significantly more accurate than Friction-style device in achieving their target torque values at baseline and 500 times fatigue.
准确地向种植体螺钉传递扭矩对于在螺钉连接中产生理想的预紧力以及防止螺钉松动至关重要。出于这个原因，机械扭矩限制装置（MTLDs）应运而生。在本研究中，测定了一种摩擦式和两种弹簧式MTLDs在基线、疲劳条件和灭菌过程后的精度。
从士卓曼（ITI）、阿斯特拉技术和CWM系统中各选取5个未使用过的MTLDs。为了测量每个MTLD的输出，使用带有三爪卡盘的数字扭矩计来固定驱动器。对MTLDs施加力，直到摩擦式在预先校准的扭矩值下释放，或者弹簧式弯曲到预先校准的极限（目标扭矩值）。记录峰值扭矩值，每个MTLD重复该过程5次。然后将MTLDs分别进行500次和1000次的疲劳试验，以及50次和100次的蒸汽灭菌处理，并在每个阶段再次记录峰值扭矩值。
所有3个系统在各阶段测量扭矩值与目标扭矩值之间的调整差异均有显著不同。在所有阶段，各系统之间的调整差异无显著不同，但在基线和500次疲劳阶段，两种不同类型之间的调整差异有显著不同。
士卓曼（ITI）装置在所有阶段与目标扭矩值的差异最小。在基线和500次疲劳试验中，弹簧式MTLDs在达到目标扭矩值方面比摩擦式装置显著更精确。
