Assessment of Efficacy of Implant Screwdrivers' During Multiple Tightening/ Untightening Cycles. An in vitro Study.

Introduction: It is unclear the number of times a screwdriver may be reused without loosening its efficacy or inducing damage to implant screws while keeping appropriate torque values.

Objective: Evaluate the effect of the screwdriver and internal threads on the tightening efficacy by assessing the reverse torque value (RTV).

Methods: The efficacy was tested with four groups of screws: two titanium groups and two gold-platted (n=5). Each screw was tightened 10 times at 20 Ncm using the screwdriver attached to ISD900 (NSK®). In the first protocol one implant was used for the five screws. In the second protocol for each screw a new implant was used. At each untightening, the RTV was measured and recorded.

Results: RTVs for Gold were statistically lower compared to the Titanium. The RTVs differed among the tested screws. In the first protocol, the first serie tightening/untightening differed statistically from the last three series.

Conclusion: Titanium screws from Zimmer Biomet achieve better RTV than gold-platted. By increasing the number cycles it is expected to have a decrease in the RTV. The extensive use of screwdrivers and the internal threads of the dental implants might be factors influencing the loss of RTV.