Does Steam Sterilization affect Accuracy of Spring- style Implant Torque Devices?
When accounting for complications over a 5 year span, Mashid et al reported that “screw loosening has been stated as the most common complication in implant” dentistry. One leading cause could be torque driver reliability.
Torque drivers include “toggle-type or friction-style,” and “beam-type or spring-style.” Many believe spring-style offer more accuracy even though accuracy becomes suspect after steam sterilization. To test the effects of steam sterilization, Mashid’s team tested 5 each from Nobel Biocare, Straumann [ITI, photo at top], and Biomet 3i [3i]). The “peak torque” of each was measured before and after steam sterilization.
Materials and Methods
All devices were tested ten times at 35 Ncm prior to steam sterilization. Sterilization of each was managed according to manufacturer directions: “Nobel Biocare devices should be dismantled for disinfection, cleaning and drying and then the parts should be assembled before sterilization. In the ITI group, dismantling of devices is proposed. Each component should be disinfected, cleaned, and dried, but sterilized separately. For 3i samples, dismantling of the device is not proposed and disinfection of the outer surface is the only protocol to be considered.” The recommended protocols and sterilizations were repeated 100 times at 134°C for 18 min, and then measured 10 times for torque accuracy.
Before steam sterilization, all the tested devices stayed within 10% of their targeted torque values. After 100 sterilization cycles, there were no significant difference in the Nobel Biocare and ITI devices. There was, however, an increase of error values in the 3i group, which showed more than a 10% difference with a maximum difference of 14% in 17% of torque measurements. The authors also reported that 3i torque devices had developed “corrosion of the spring in the handle” that may have contributed to its inaccuracy.
Different research by Santos et al, tested Biomet 3i, Nobel Biocare, Straumann, and Conexao at 20 Ncm and reported 62.5% were within 10% of the tested value. However, when tested at a 32 Ncm target, “only 33.3% of all values from each manufacturer were considered accurate,” with ITI being the most consistent in accuracy for both values. During the Santos testing, each torque device had been in clinical use for less than 2 years. With the amount of use and “sterilization protocols” unknown, their findings might better reflect the real world of clinical dentistry than would a highly controlled, laboratory testing protocol. The reports reinforce the need for manufacturer recalibration with frequency matched to use.