In Vitro Evaluation of Manual Torque Values Applied to Implant-Abutment Complex by Different Clinicians and Abutment Screw Loosening.
Abstract
Preload
is applied to screws manually or using a torque wrench in dental
implant systems, and the preload applied must be appropriate for the
purpose. The aim of this study was to assess screw loosening and
bending/torsional moments applied by clinicians of various specialties
following application of manual tightening torque to combinations of
implants and abutments. Ten-millimeter implants of 3.7 and 4.1 mm
diameters and standard or solid abutments were used. Each group
contained five implant-abutment combinations. The control and
experimental groups comprised 20 and 160 specimens, respectively.
Implants in the experimental group were tightened by dentists of
different specialties. Torsional and bending moments during tightening
were measured using a strain gauge. Control group and implants with
preload values close to the ideal preload were subjected to a dynamic
loading test at 150 N, 15 Hz, and 85,000 cycles. The implants that
deformed in this test were examined using an optical microscope to
assess deformities. Manual tightening did not yield the
manufacturer-recommended preload values. Dynamic loading testing
suggested early screw loosening/fracture in samples with insufficient
preload.
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