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.
Highlights
Dental implants offer extensive treatment options for patients who are completely or partially edentulous [1]
The reasons for the results found by analysis of variance (ANOVA) were investigated using the Bonferroni test
Of the experimental group samples subjected to dynamic fatigue testing (n = 20), 9 (45%) had screw fractures and 8 (40%) had an opening on the pressured side
Summary
Dental implants offer extensive treatment options for patients who are completely or partially edentulous [1]. Osseointegrated dental implants are the goal in clinical practice; there may be complications such as screw loosening and screw, implant, or denture fractures [1,2,3]. Preload applied by rotational movement of abutment screws is essential for retention in systems in which the connection between the implant and abutment is maintained via a screw. The elastic recovery feature of abutment screws creates a connection force that keeps components together [4]. The preload forms a compressive force between the head of abutment screws and the abutment platform, the abutment and implant, and the abutment and the implant interior grooves, and so holds these components together [5]
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