Effect of washers on reverse torque displacement of dental implant gold retaining screws.
BACKGROUND
Gold screw loosening is a frequent problem that affects dental implants.


OBJECTIVE
This study determined the effect of spring washers on gold screw displacements during applied removal torque in dental implants.


METHODS
A 3-unit fixed partial denture was cast in semiprecious alloy and fixed to 2 dental implants with gold-retaining screws. Implants were embedded in acrylic resin and restrained from movement. A miniature load sensor was attached to a torque controller handpiece to accurately measure the time and torque needed to completely loosen the gold screws. Rotational displacements were calculated for 4 experimental setups, involving washers placed on (a) both, (b) the mesial, (c) the distal, and (d) no implants. Screw displacement data were compared between implants in all 4 combinations by means of paired t tests.


RESULTS
Gold screws with underlying conical spring washers underwent on average up to 35% (14.1 microm) more rotational displacement during applied removal torque than those without washers.


CONCLUSIONS
Inclusion of a conical spring washer significantly increased the amount of rotational displacement needed to completely loosen an implant gold retaining screw.
Korioth
T W
TW
Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, MN 55455, USA. korio001@tc.umn.edu
Cardoso
A C
AC
Versluis
A
A
D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003781:Denture Retention / Q000295:instrumentation*; D003830:Denture, Partial, Fixed; D006047:Gold Alloys; D006801:Humans; D019415:Torque
D006047:Gold Alloys