Comparative In-Vitro Evaluation of Torque Accuracy in Spring-Type vs. Toggle-Design Wrenches in Implant Dentistry

Abstract Objective: This in vitro study compared the accuracy and reliability of spring-type versus toggle-design torque wrenches used in implant dentistry, evaluating torque deviation at clinically relevant settings. Materials and Methods: Twelve new, factory-calibrated torque wrenches (six spring-type and six toggle-design) were tested at two torque levels (spring: 15 and 35 N·cm; toggle: 10 and 30 N·cm). Each device underwent 30 torque applications per setting using a digital torque meter under standardized laboratory conditions. Primary outcomes were mean percentage error, absolute torque deviation (N·cm), and frequency of torque deviations beyond ±0.5% of target. Statistical analysis included Mann-Whitney U tests and Wilcoxon signed-rank tests. Results: Both wrench types exhibited substantial deviations from manufacturer-specified values, with over 90% of applications exceeding ±0.5% tolerance. Spring-type wrenches showed mean percentage errors of 15.74% at 15 N·cm and 5.06% at 35 N·cm. Toggle-design wrenches demonstrated 14.66% error at 10 N·cm and 7.96% at 30 N·cm. Error frequency was 94.71% for spring-type and 92.5% for toggle-design wrenches. Toggle-design wrenches showed significantly lower absolute error at high torque settings (P = 0.01), but no significant difference in low torque ranges (P = 0.15). Conclusion: Both spring-type and toggle-design torque wrenches exhibit notable torque inaccuracies, especially at lower torque settings. Toggle-design wrenches demonstrated greater accuracy at higher torque levels. Given the high frequency of torque deviation, routine calibration verification and consideration of supplemental verification methods are recommended.