Titanium dioxide nanoparticles reinforced experimental resin composite for orthodontic bonding

The aim of this laboratory study was to evaluate the effect of titanium dioxide (TiO₂) nanoparticles reinforced experimental adhesive resin for orthodontic bonding. The experimental resin (bis-Phenol-A free) was prepared using urethane dimethacrylate, hydroxypropyl methacrylate, camphorquinone and N, N-cyanoethyl methylaniline. TiO₂ nanoparticles were added at 1 weight-% and 3 weight-% of the experimental resin composite and were labeled as RC1 (1 weight-% TiO₂) and RC3 (3 weight-% TiO₂), and non-reinforced resin composite was used as control (RC). A total of 90 extracted human premolars were randomly assigned into 3 groups. In group RC, metal orthodontic brackets were bonded to the enamel surface using experimental resin (without TiO₂). In the group RC1, the brackets were bonded using resin RC1, and in the group RC3, the brackets were bonded using resin RC3. Fifteen randomly selected specimens from each study group were subjected to artificial aging, and the remaining fifteen served for the baseline adhesion strength measurements. Adhesion strength was measured and recorded using a universal testing machine. Fluidity and anti-bacterial activity of the experimental and reinforced resins were determined. The highest adhesion strength at baseline was seen in group RC1 (13.2 ± 1.8 MPa), and the lowest values was seen in the group RC (12.5 ± 1.8 MPa). Following thermo-cycling, the highest adhesion strength was observed in the group RC1 (12.4 ± 2.4 MPa) and the lowest values were seen in the group RC (10.6 ± 1.6 MPa). A significant difference (ANOVA) was observed between the groups (both baseline and thermo-cycled groups) except for group RC1 (p > 0.05). The resin in the RC group demonstrated more fluidity compared to the experimental groups. Among the experimental groups, group RC3 demonstrated less fluidity compared to group RC1. The colony forming units (CFUs) were high in group RC and the least values were found in group RC1. Addition of 1% TiO₂ to the BPA and bis-GMA free experimental resin demonstrated promising flow and anti-bacterial effect without compromising the adhesion strength or chemical properties. (paper)