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

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.

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

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.

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.

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.