Abstract:
This in vitro investigation compared the effect of using either
gold or titanium retaining screws on preload in the dental implant-
abutment complex. Inadequate preload can result in
screw loosening, whilst fracture may occur if preload is excessive.
These are the most commonly reported complications
in implant-retained prostheses, and result in unscheduled,
costly and time-consuming visits for the patient and the
clinician. This study investigated changes in preload generation
after repeated torque applications to gold and titanium
screws. The test set-up consisted of an implant body, a cylindrical
transmucosal abutment, and the test samples of gold
and of titanium retaining screws. The implant bodies were
anchored using a load cell, and the transmucosal abutments
were attached using either gold or titanium retaining screws.
A torque gauge was used to apply torque of 20Ncm, 32Ncm,
and 40Ncm to the retaining screws. The preloads generated
in each screw type were compared at each torque setting,
and after repeated tightening episodes. In addition, the effect
of applying torque beyond the manufacturers’ recommendations
was also examined. Gold retaining screws were found
to achieve consistently higher preload values than titanium
retaining screws. Preload values were not significantly different
from the first to the tenth torque cycle. Titanium screws
showed more consistent preload values, albeit lower than
those of the gold screws. However due to possible galling
of the internal thread of the implant body by titanium screws, gold screws remain the retaining screw of choice. Based on
the findings of this study, gold retaining screws generate better
preload than titanium. Torque beyond the manufacturers’
recommendations resulted in a more stable implant complex.
However, further investigations, with torque applications repeated
until screw breakage, are needed to advise on ideal
maintenance protocols.
