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J Prosthet Dent. 1999 Sep;82(3):312-6.

Effect of washers on reverse torque displacement of dental implant gold retaining screws.

Author information

1
Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, MN 55455, USA. korio001@tc.umn.edu

Abstract

STATEMENT OF THE PROBLEM:

Gold screw loosening is a frequent problem that affects dental implants.

PURPOSE:

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

MATERIAL AND 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.

CONCLUSION:

Inclusion of a conical spring washer significantly increased the amount of rotational displacement needed to completely loosen an implant gold retaining screw.

PMID:
10479258
DOI:
10.1016/s0022-3913(99)70086-7
[Indexed for MEDLINE]

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