An in vitro assessment of the accuracy of new and in-use torque-limiting devices

Statement of problem: Recent studies have shown that torque-limiting devices (TLDs) do not meet their torque targets and are affected by factors such as the use of the TLDs and the sterilization processes used. Purpose: The purpose of this in vitro study was to investigate the accuracy of TLDs currently in use in the Advance Education Program in Prosthodontics at the New York University College of Dentistry. Material and methods: Five new and 46 in-use TLDs (Nobel BioCare) from the implant kits of the graduate students were evaluated. One investigator was trained and calibrated before testing and after every 10 evaluations. A 3-jaw chuck was mounted on the center of a cap testing device by using the provided mounting screws. A LOCATOR torque driver was clamped into the chuck, and a torque wrench driver was attached to it. The device was placed on a flat table with direct overhead lighting that allowed the investigator to have a consistent view of the notches on the TLDs. A piece of cardboard was attached to the device to ensure that the investigator could not see the readouts. The blinded researcher inserted the wrench and applied the appropriate torque force at the designated notches while another researcher recorded the results. Two readings were made for each TLD at 15, 35, and 45 Ncm. A 2-way ANOVA and an intraclass correlation coefficient to test for intraclinician reliability were performed by using a statistical software program (α=.05). Results: Two TLDs were damaged and not tested. The 2-way ANOVA demonstrated no significant difference (P>.05) between graduate students in year 1, 2, and 3 or between the autoclaved and new TLDs. The intraclass correlation coefficient was 0.861 for 15 Ncm, 0.589 for 35 Ncm, and 0.764 for 45 Ncm. Conclusions: In this in vitro study, new and used TLDs all met the recommended torque values. No significant differences were found among groups, suggesting that autoclaving and use did not affect the accuracy of the TLDs tested.