Objective:

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

Materials and Method:

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.

Results:

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.

Conclusion:

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.

Keywords: Bone Cement, Mini screw, Pull-out, Shear