Efficacy of mini implant ring apparatus on the stability of mini screws in different bone densities

The aim of this study is to evaluate the influence of cortical bone density on mini screw stability and to investigate the efficacy of mini implant ring apparatus (MIR) on the stability of mini screws in different bone densities. For this purpose, 108 conical mini screws (1.6 mm diameter, 8 mm length), 54 MIR apparatus and artifical bone samples with different cortical densities were used in this study. Control groups consisted of mini screws applied to artificial bone samples with densities of 20, 30 and 40 pcf whereas experiment group included MIR supplemented mini screws mounted to artificial bone samples with the same densities as the former group. Maximum insertion torque (MIT), force resistance (FR) and maximum removal torque values (MRT) were measured for each group. The findings were evaluated statistically. Statistically significant differences were found among MIT, FR and MRT values measured in different cortical bone densities (p<0.001). MIT, FR and MRT values for MIR group were found to be statistically significantly higher than those for control group in all cortical bone densities (p<0.001). To conclude, increase in cortical bone density also enhances the primary stability of mini screws. Likewise, stability of MIR supplemented mini screws increased accordingly with the bone densities. Application of MIR apparatus influences anchorage values in a positive manner Key words: Mini screws, Mini implant ring (MIR) apparatus, cortical bone density, primary stability.