Evaluation of the Effects of the Universal Bond on the Shear Bond Strength of Orthodontic Brackets Bonded with 2 Types of Composites Containing Primers

Aim: The primer-containing composites, which eliminate the bonding step, decrease clinical time and securely attach the bracket to the tooth. Given the significant role of bonding in the bond strength of orthodontic adhesives, this study aims to investigate the effect of using a universal bond with two types of primer-containing composites on the bond strength of these composites. Methods: Sixty healthy premolars were collected and divided into four equal groups: GC Ortho Connect composite, GC Ortho Connect composite with a universal bond, OrthoCem composite, and OrthoCem composite with a universal bond. The shear bond strength was measured using a universal testing machine, and the residual adhesive index was measured using a stereomicroscope at a 10x magnification. Results: The shear bond strengths of the GC Ortho Connect group without a universal bond, the GC Ortho Connect group with a universal bond, the OrthoCem group with a universal bond, and the OrthoCem group without a universal bond were calculated to be 21.54, 12.88, 12.37, and 11.68 MPa, respectively. The analysis of variance (ANOVA) showed that the GC Ortho Connect group without a universal bond had a significantly higher shear bond strength than the other groups. The results also indicated that the universal bond reduced the shear bond strength in the GC Ortho Connect composite (p-value 0.001) and had no significant effect on the shear bond strength of the OrthoCem composite (p-value=1.000). Conclusion: While the application of a universal bond considerably diminishes the shear bond strength in the GC Ortho Connect composite, it does not exert a significant influence on the OrthoCem composite. This suggests that the effectiveness of a universal bond may be dependent on the specific composite used, necessitating further investigations into optimizing bonding methods for different composite materials in orthodontics.