Abstract
BackgroundDespite the high survival rate of dental implants, screw loosening is frequently reported. Screw loosening can cause a misfit of the implant-abutment connection leading to peri-implantitis or abutment screw fracture. Therefore, studies about related factors and mechanism of screw loosening are needed. The aim of this study was to evaluate the decreasing pattern of removal torque values (RTVs) of a combined cone and octalobule index implant-abutment connection under different numbers of mechanical loading cycles.Materials and methodsThe study was performed in accordance with ISO 14801:2007. Eighty-four implants with the combined cone and octalobule index implant-abutment connection (PW Plus dental implant system, PW Plus Company) were used. All abutment screws were tightened 30 N cm twice with a 10-min interval. The control group was without cyclic loading and the experimental groups underwent different numbers of loading cycles until 2,000,000 cycles. Then, the abutment screws of all samples were untightened to measure the RTVs. The data were analyzed using ANOVA and Tukey’s HSD test.ResultsThe RTVs of the control group decreased 7.78% compared to the insertion torque. All experimental groups from 50,000 to 2,000,000 cycles showed significant decreases in RTVs compared to the control group (P < 0.05). RTVs in the group of 50,000 cycles to 1,800,000 cycles did not change significantly, but there was a significant reduction of RTVs in the group of 2,000,000 cycles when compared to the group of 50,000 cycles (P < 0.05).ConclusionsAccording to the setting condition for the fatigue test complied to ISO 14801:2007, the RTVs of the combined cone and octalobule index implant-abutment connection reduced significantly after 50,000 cycles and did not change significantly until 2,000,000 cycles.
Highlights
Despite the high survival rate of dental implants, screw loosening is frequently reported
According to the setting condition for the fatigue test complied to ISO 14801:2007, the removal torque values (RTVs) of the combined cone and octalobule index implant-abutment connection reduced significantly after 50,000 cycles and did not change significantly until 2,000,000 cycles
The mean initial RTV of the control group was 27.67 N cm, a decrease of 7.78% compared to the insertion torque
Summary
Despite the high survival rate of dental implants, screw loosening is frequently reported. Despite the high survival rate of implants, technical complications, such as screw loosening, are frequently reported [1,2,3]. The Octatorx-cone connection is a combination of a Morse taper connection with a 6° tapered angle and star-shaped “octalobules” indices with eight rounded points [9] (Fig. 1). This Octatorx-cone connection provides an anti-rotational characteristic and surface frictional resistance at the implant-abutment interface, which may prevent micromovement and screw loosening during function
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