Effect of Abutment Type and Tightening Sequence on Torque Maintenance Capacity after Mechanical Cycling in Splinted Implant-Supported Restorations

Abstract

The aim of this study was to compare the screw removal torque of mini-conical prosthetic components and straight trunnion of indexed morse taper implants after mechanical cycling. The sample consisted of 40 implants and 20 mini-conical prosthetic components (MC group) and 20 straight trunnion components (ST group). Each group consisted of 10 specimens, with 2 implants in each, and cobalt–chromium metallic crowns were screwed into each sample. The components of the MC group received a torque of 20 N-cm with a digital torque wrench, and after 10 min were retightened with the same value as the initial torque. The components of the ST group received a torque of 30 N-cm, with a digital torque wrench, and after 10 min, they were retightened with the same value. The screws of the respective crowns of the two groups received a torque of 10 N-cm and after 10 min were retightened with the same value. Each group was subjected to the fatigue test in a mechanical cycler at 2,000,000 cycles, with a load of 250 N and frequency of 4 Hz. At the end of the fatigue test, the loosening torque of each screw of the specimens was measured through a digital torque wrench. The data were analyzed by two-way ANOVA and a Tukey test. In both groups, there were loss of torque. The results showed no statistic difference between MC and ST groups (p > 0.05).

Effect of Antirotational Two-Piece Titanium Base on the Vertical Misfit, Fatigue Behavior, Stress Concentration, and Fracture Load of Implant-Supported Zirconia Crowns

“…As a baseline, immediately after the storage period, the interfaces between the titanium bases and the restorations of each specimen were analyzed using an optical microscope (Discovery V20, Zeiss, Jena, Germany) at a magnification of 40×, and the vertical misfit was measured in micrometers. Ten measurements of the interfaces were taken on each side of the restorations (4 regions (buccal, mesial, distal, and palatal)) by a single trained examiner [ 29 ]. After fatigue cycling, the same protocol was applied to measure the vertical misfit in the long-term simulation.…”

“…For this purpose, forty specimens (n = 20 per group) were placed in a stainless-steel base with a 30-degree angulation relative to the ground, following ISO 14801, to assess the aging effect. Subsequently, the specimens were subjected to a load of 200 N at a frequency of 2 Hz for 2 × 10 6 cycles ( Figure 2 ) [ 10 , 29 ].…”

“…For this purpose, forty specimens (n = 20 per group) were placed in a stainlesssteel base with a 30-degree angulation relative to the ground, following ISO 14801, to assess the aging effect. Subsequently, the specimens were subjected to a load of 200 N at a frequency of 2 Hz for 2 × 10 6 cycles (Figure 2) [10,29]. All aged specimens were re-evaluated for vertical misfit and torque maintenance capacity to assess the effect of cyclic fatigue on these parameters [10].…”