Evaluation of the torque application accuracy of differently manufactured mechanical torque-limiting devices

The preload force applied to screw components used in implant-supported prostheses plays a critical role in long-term success by preventing screw loosening. This study aimed to evaluate the accuracy of various types and brands of new and clinically used mechanical torque-limiting devices (MTLDs) in achieving target torque values. A total of 18 devices with two different mechanisms—spring and friction types—were included (Dentis, XGate, Grealth/Universal). For each brand, three new and three clinically used (for at least six months) devices were selected. According to manufacturer instructions, target torque values were set at 20 and 30 Ncm for Dentis, 15 and 30 Ncm for XGate, and 15, 20, and 30 Ncm for Grealth. All measurements were performed using a high-precision Mark-10 Cap Torque Tester TT01-100 (Mark-10 Corp., USA) by a single operator, applying torque for approximately 4 seconds. Each torque level was repeated 10 times per device. Data were recorded using MESURLite (Mark-10 Software) at a sampling rate of 10 Hz. All MTLDs examined in the study exhibited mean deviations within the clinically acceptable range of ±10%. No statistically significant differences were found between brand, mechanism type, or usage condition (p>0.05). However, subgroup analyses revealed a significant Torque × Usage interaction for Dentis devices (p<0.001), with higher deviations at 30 Ncm in new devices and at 20 Ncm in used ones. In Grealth (Universal) devices, deviations at 15 Ncm exceeded the acceptable limit, and new devices at 30 Ncm approached the threshold, although these differences were not statistically significant (p>0.05). In XGate devices, greater variation was observed in the used group at 15 Ncm, with some measurements exceeding 15% deviation, yet the results were not statistically significant (p=0.052). Brand and usage condition were found to be more influential on device accuracy than mechanism type. For clinical reliability, regular calibration of all devices, more frequent validation at lower torque levels, and pre-use testing of new devices are recommended.