Physicochemical Properties and White Spot Lesion Inhibition of an Orthodontic Adhesive Containing Zinc Oxide Nanoparticles: An In Vitro Study

Aim This study aimed to experimentally synthesize a homogeneous orthodontic adhesive containing zinc oxide (ZnO) nanoparticles and to evaluate its physicochemical properties and its indirect effects on caries-related fluorescence and demineralization associated with Streptococcus mutans biofilm activity.Methods This in vitro study evaluated ۳۰ extracted premolars that were subjected to bracket bonding with three types of adhesives: (I) experimentally synthesized adhesive without ZnO (basic/control), (II) experimentally synthesized adhesive containing ۱.۶ wt% ZnO nanoparticles (optimized), and (III) American Orthodontics (AO) adhesive (Gold standard). To assess the antibacterial activity of the adhesives, the teeth were immersed in Streptococcus mutans suspension after bracket bonding, and DIAGNOdent was used to assess the formation of white spot lesions (WSLs) at different time intervals (۰,۷,۱۴,۲۱ and ۲۸ days). The shear bond strength (SBS) and adhesive remnant index (ARI) scores, as well as the water sorption and water solubility of the adhesives, were evaluated. Data were analyzed using one-way ANOVA, repeated-measures ANOVA, Tukey, Kruskal-Wallis, and t-tests (α=۰.۰۵). Results The optimized adhesive containing ZnO nanoparticles demonstrated clinically acceptable SBS values comparable to those of the control and AO adhesives (P = ۰.۰۸۶). DIAGNOdent values were significantly lower in the optimized adhesive group compared with the basic and AO adhesives at all time intervals (P < ۰.۰۰۱), indicating reduced caries-related fluorescence and demineralization potential. Water sorption and water solubility of the optimized and basic adhesives were within the acceptable range according to ISO ۴۰۴۹ and were significantly lower than those of the AO adhesive (P < ۰.۰۵). Zn ion release from the optimized adhesive remained substantially below reported cytotoxic thresholds.ConclusionThe experimentally synthesized orthodontic adhesive containing ۱.۶ wt% ZnO nanoparticles demonstrated favorable physicochemical properties and lower DIAGNOdent values associated with reduced cariogenic activity around orthodontic brackets. In addition, Zn ion release remained well below reported cytotoxic levels. Further microbiological and clinical studies are required to confirm the long-term antimicrobial efficacy and clinical performance of this material.

کلیدواژه ها:

Dental bonding ، nanoparticles ، Orthodontic Brackets ، Shear strength