This ex
perimental study was designed to examine whether screw head design influenced the angle of a
pplication of a screwdriver at which failure of engagement or stri
pping of the screw head occurred.
Materials and methods
<
p>Four different screw head designs (slot, cross, square, star) were tested in a custom-made jig that was designed to enable the screws to be tested over a range of angles of a
pplication of the res
pective screwdrivers, to determine whether the screw head design influenced the torque value at which the screw head stri
pped or failure of driver engagement occurred.
Results
<
p>The results fell clearly into 2 grou
ps: The slot and cross designs gave the highest torque values at all angles, while the torque values for the square and star designs dro
pped to a low value with increasing angulation between the screw and driver. These differences were significant (
P < .001).
Conclusions
<
p>Although this ex
perimental situation cannot be entirely extra
polated to the clinical situation, it indicates that the slot or cross design may offer an advantage in regions of difficult access where the angulation of the screwdriver to the screw may of necessity be increased.