ACCURACY OF THE IMPLANT TORQUE WRENCH FOLLOWING TIME IN CLINICAL SERVICE

Thirty-five implant torque wrenches were rested for torque delivery ac curacy. Seven of these drivers had a 10-Ncm value, 12 had a 20-Ncm val ue, 10 had a 30-Ncm value, and six had a 35-Ncm value. All of the wren ches had been in clinical service for a minimum of 1 month or a maximu m of 3 years and were assumed by the clinicians to be fully effective in delivering the required torque values. Torque delivery accuracy was determined using a Tohnichi torque wrench calibrated to +/- 1% of the scale value. All torque wrenches had been subjected to steam steriliz ation following clinical use. Data collected on all wrenches included (1) age since purchase, (2) number of sterilization cycles to which ea ch wrench had been subjected during the use period, and (3) 10 sequent ial torque readings using the Tohnichi wrench as the torque reading de vice. The results of this study showed that there was no significant c orrelation of delivered torque with (1) age or (2) number of steriliza tion cycles. Furthermore, in each torque category there were torques b oth above and below the control values. For the 10-Ncm torque wrenches , the largest value was 455.0% greater than the control, the largest v alues were 41.6% greater for 20-Ncm wrenches, 17.0% greater for the 30 -Ncm torque wrenches, and 58.6% greater for the 35-Ncm wrenches. Corro sion oi the spring in the handle of the torque wrench was found to be the reason for the 455.0% value.