the effect of sterilization and number of use on the accuracy of friction-style mechanical torque limiting devices for dental implants

background: mechanical torque limiting devices (mtlds) are necessary tools to control a peak torque and achieving target values of screw component of dental implants. due to probable effect of autoclaving and number of use on the accuracy of these devices, this study aimed to evaluate the effect of sterilization and number of use on the accuracy of friction-style mechanical torque limiting devices (f-s mtlds) in achieving their target torque values. materials and methods: peak torque measurements of 15 new f-s mtlds from three different manufacturers (astra tech, biohorizons, dr. idhe) were measured ten times before and after 100 steam sterilization using a digital torque gauge. to simulate the clinical situation of aging (number of use) target torque application process was repeated 10 times after each sterilization cycle and the peak torque values were registered. comparison of the mean differences with target torque in each cycle was performed using one sample t test. considering the type of mtlds as inter subject comparison, one-way repeated measure anova was used to evaluate the absolute values of differences between devices of each manufacturer in each group (α = 0.05). results: the results of this study in dr. idhe group showed that, mean of difference values signifi cantly differed from the target torque ( p = 0.002) until 75 cycles. in astra tech group, also mean of difference values with under estimation trend, showed a signifi cant difference with the target torque ( p < 0.001). mean of difference values signifi cantly differed from the target torque with under estimation trend during all the 100 cycles in biohorizons group ( p < 0.05). conclusion: the torque output of each individual device stayed in 10% difference from target torque values before 100 sterilization cycles, but more than 10% difference from the target torque was seen in varying degrees during these consequent cycles. key words: calibration, dental implants, equipment failure, torque