The Effect of Aging on the Accuracy of New Friction-Style Mechanical Torque Limiting Devices for Dental Implants

Objective: High variability in delivering the target torque is reported for friction- style mechanical torque limiting devices (F-S MTLDs). The effect of aging (num- ber of use) on the accuracy of these devices is not clear. The purpose of this study was to assess the effect of aging on the accuracy ( + 10% of the target torque) of F-S MTLDs. Materials and Methods: Fifteen new F-S MTLDs and their appropriate drivers from three different implant manufacturers (Astra Tech, Biohorizon and Dr Idhe), five for each type, were selected. The procedure of peak torque measurement was performed in ten sequences before and after aging. In each sequence, ten repeti- tions of peak torque values were registered for the aging procedure. To measure the output of each device, a Tohnichi torque gauge was used. Results: Before aging, peak torque measurements of all the devices tested in this study falled within 10% of their preset target values. After aging, a significant dif- ference was seen between raw error values of three groups of MTLDs (P<0.05). More than 50% of all peak torque measurements demonstrated more than 10% difference from their torque values after aging. Conclusion: Within the limitation of this study, aging as an independent factor affects the accuracy of F-S MTLDs. Astra Tech MTLDs presented the most con- sistent torque output for 25 Ncm target torque.