Antibacterial and physicochemical properties of a zinc oxide nanoparticle-modified orthodontic adhesive : An in vitro study.

PURPOSE

White spot lesions (WSLs) can result from bacterial plaque around orthodontic brackets, leading to enamel demineralization. While other preventive strategies rely on patient compliance, incorporating zinc oxide (ZnO) nanoparticles into adhesives offers antimicrobial protection, independent of compliance. This study aimed to develop a ZnO-containing adhesive and evaluated its antibacterial and mechanical properties for clinical application.

METHODS

This in vitro study, conducted at Shahid Beheshti University of Medical Sciences, sampled 30 extracted premolar teeth and randomly assigned them to three groups: (1) control (synthesized adhesive without ZnO), (2) ZnO (1.5% ZnO nanoparticles), and (3) XT (Transbond XT, 3M, St. Paul, MN, USA). The adhesive's antibacterial effect was assessed using Streptococcus mutans biofilm inhibition, while mechanical and physicochemical properties were evaluated by measuring shear bond strength (SBS), adhesive remnant index (ARI), degree of conversion (DC), water sorption, water solubility, and microhardness. Data were analyzed using one-way analysis of variance (ANOVA), Tukey's honestly significant difference (HSD), Kruskal-Wallis test, and Mann-Whitney test using SPSS software (IBM, Armonk, NY, USA). P-values less than 0.05 were considered statistically significant.

RESULTS

Statistically significant differences were found among the three groups with respect to SBS (P = 0.023), microhardness (P < 0.001), antibacterial activity (P < 0.001), water sorption (P = 0.003), and water solubility (P < 0.001). No significant differences were observed in DC or ARI. Post hoc tests showed that ZnO outperformed the control in all properties except SBS and did not differ significantly from XT in tested properties.

CONCLUSION

Incorporating 1.5% ZnO nanoparticles into the synthesized adhesive enhanced antibacterial properties and inhibited biofilm formation without compromising bond strength, DC, water sorption, water solubility, or microhardness. Given its superior antibacterial efficacy over Transbond XT, the ZnO adhesive shows potential as a viable option for orthodontic bonding.