The effect of screwdriver angle variation on the off-axis implant abutment system and hexalobular screw

Abstract

Statement of problem: A recently introduced hexalobular screw system allows for off-axial screw channel access. The screwdriver angle input torque relative to the screw axis output torque has not been established. Purpose: The purpose of this in vitro study was to evaluate the effect of maximum angulation on the abutment-implant screw connection and torque values for a hexalobular screw system and to determine how input versus output varies with the angle of the screwdriver. Material and methods: Twenty angulated abutments attached to implant fixtures were tightened to the manufacturers' prescribed torque at 2 different input angles: 0 and 28 degrees off axial (n=10/group). Input and reverse torque values were recorded by using calibrated torque sensor devices and compared for significant differences by using the Mann-Whitney U test. Fifty hexalobular screws were subjected to screwdriver angle variations of 0, 10, 15, 25, and 28 degrees (n=10/group). The input torque (screw head) and output torque (screw body) were recorded. The Kruskal-Wallis rank sum test and the post hoc Dunn test were used for statistical analysis of the output torque (α=.05). Results: Significant differences in mean reverse torque existed (P