Torque Accuracy of Spring-Style Dental Torque Wrenches After Repeated Mechanical Loading and Sterilization: An In Vitro Study.

This in vitro study evaluated the torque accuracy of spring-style mechanical torque-limiting devices (MTLDs) from three manufacturers under clinically simulated conditions. Nine devices (Implance, Astra Tech, and DIO) were tested with a digital torque tester. Target torque values were 25 and 35 Ncm for Implance and Astra Tech and 20 and 35 Ncm for DIO. Each device underwent 40 experimental cycles, including baseline measurement, mechanical fatigue by 20 loading repetitions at target torque, post-fatigue measurement, and steam sterilization. Torque difference and percentage deviation from target value were calculated; deviations exceeding ±10% were classified as outside the acceptable range. Torque difference and percentage deviation were analyzed using aligned rank transform (ART) mixed ANOVA with Holm-adjusted comparisons. The experimental cycle significantly affected torque difference in all manufacturers, whereas the measurement stage did not. Percentage deviation was significantly associated with experimental cycle, manufacturer, and their interaction. Overall median percentage deviation was 11.43% for Implance, 3.33% for Astra Tech, and 16.67% for DIO. Torque accuracy was manufacturer-dependent and changed over repeated experimental cycles comprising mechanical loading and sterilization, supporting verification before clinical use and periodic recalibration of spring-style MTLDs.