ABSTRACT

The purpose of this study was to determine whether bone cement increased the resistance of miniscrews against pull-out and shear forces.

Sixty commercially available miniscrews were placed into bovine bone samples (one each) at a 90° angle, using a custom-made orientation jig and controlling torque (30 N-cm) and rotation (20 rpm) with a rechargeable screwdriver. The miniscrews were inserted using three different methods: self-drilling, predrilling, and predrilling with bone cement application. Pull-out strengths and shear tests were performed using a universal testing machine.

Nonparametric Kruskal-Wallis tests were used for comparisons between groups, and Bonferroni-adjusted Mann-Whitney U tests were used to detect different group(s) (α/3=0.016). There was a statistically significant difference between the pull-out strengths of the groups (p<0.01). The self-drilling group had a significantly lower pull-out strength at failure than the other groups (p<0.016). The pullout strengths of the miniscrews placed with bone cement had a significantly higher pull-out strength than the predrilling group. In shear tests, there was no statistically significant difference among the groups.

This study is the first report demonstrating the effects of bone cement on stability and resistance to failure at the bone-miniscrew interface. These results show that the use of miniscrews with bone cement is a promising method that may extend the limits of force application.