ABSTRACT

The aims of this study were to determine the amount of mini-implant deflection under orthodontic loading and examine the effectiveness of a newly designed ring (mini-implant ring - MIR) placed at the collar of mini-implants.

A total of 48 mini-implants were applied to the bone samples obtained from the ileum of bovine. In the study group 24 mini-implants were applied with MIR and remaining mini-implants were applied without MIR and were assigned as control. All mini-implants were subjected to a tangential force load of 200 g perpendicular to the screw, and displacement of screws was measured in millimeters by an Instron Universal Testing machine. After loading test, each mini-implant was removed, and the cortical bone thicknesses of the samples were measured. According to the cortical thickness of the samples, study and control groups were sub-grouped as having thin and thick cortical bone.

The mean displacement values of mini-implants inserted with MIR was significantly lower when compared with that of mini-implants inserted without MIR under 200 g force (p<0.001). Cortical bone thickness had an effect on the displacement of mini-implants of the control group. However, mean displacement, hence stability didn't differ significantly with respect to cortical bone thickness if the mini-implants were applied with MIR (p>0.05).

MIR might be a useful auxiliary to mini-implants especially in patients with thin cortical bone.