Investigating the effect of incorporating nanosilver/nanohydroxyapatite particles on the shear bond strength of orthodontic adhesives

Introduction: Development of clinically acceptable orthodontic adhesives with additional anti-microbial and remineralizing features could be undertaken only if their mechanical properties have also been considered. The purpose of this study was to investigate the effect of incorporating Silver and Hydroxyapatite (HA) nanoparticles on the shear bond strength (SBS) of an orthodontic adhesive. Methods: Silver and HA nanoparticles were prepared and inspected by scanning electron microscopy and EDAX analysis. The nanoparticles were added to the primer of Transbond XT in 1%, 5% and 10% silver concentrations. Each compound (along with a control) was used for bonding stainless steel brackets to 12 human premolars (48 in total) and the SBS of all samples, along with their ARI scores were measured. Results: The SBS of the control, 1%, 5% and 10% nanoparticle groups were 12.06 +/- 5.48, 20.66 +/- 5.72, 10.77 +/- 8.16 and 5.40 +/- 2.00 MPa, respectively. A significant difference existed between all study groups (p < 0.05), except for the control-5% and 5%-10% study groups (p = 0.99 and p = 0.35). There was no statistically significant difference in distribution of ARI scores across the study groups (p = 0.44). Conclusions: Incorporation of silver/HA nanoparticles containing 5% and 1% silver maintains and increases the SBS of orthodontic adhesives, respectively, whereas increasing the amount of particles to 10% has an undesirable effect when compared to the control group.