Antimicrobial properties of poly (methyl methacrylate) acrylic resins incorporated with silicon dioxide and titanium dioxide nanoparticles on cariogenic bacteria

AIM: To assess the effects of adding nano-titanium dioxide (nano-TiO(2)) and nano-silicon dioxide (nano-SiO(2)) and their mixture to poly (methyl methacrylate) (PMMA) to induce antimicrobial activity in acrylic resins. MATERIALS AND METHODS: Acrylic specimens in size of 20 mm × 20 mm × 1 mm of 0.5% and 1% of nano-TiO(2) (21 nm) and nano-SiO(2) (20 nm) and their mixture (TiO(2)/SiO(2) nanoparticles) (1:1 w/w) were prepared from the mixture of acrylic liquid containing nanoparticles and acrylic powder. To obtain 0.5% and 1% concentration, 0.02 g and 0.04 g of the nanoparticles was added to each milliliter of the acrylic monomer, respectively. Antimicrobial properties of six specimens of these preparations, as prepared, were assessed against planktonic Lactobacillus acidophilus and Streptococcus mutans at 0, 15, 30, 45, 60, 75, and 90 min follow-up by broth dilution assay. The specimens of each group were divided into three subgroups: Dark, daylight, or ultraviolet A (UVA). The percent of bacterial reduction is found out from the counts taken at each time point. STATISTICAL ANALYSIS: Data were analyzed using one-way analysis of variance and Tukey's post hoc analysis. RESULTS: Exposure to PMMA containing the nanoparticles reduced the bacterial count by 3.2–99%, depending on the nanoparticles, bacterial types, and light conditions. Planktonic cultures of S. mutans and L. acidophilus exposed to PMMA containing 1% of TiO(2)/SiO(2) nanoparticles showed a significant decrease (P < 0.001) (98% and 99%, respectively) in a time-dependent manner under UVA. The S. mutans and L. acidophilus counts did not significantly decrease in PMMA containing 0.5% nano-TiO(2) and PMMA containing 0.5% nano-SiO(2) in the dark. No statistically significant reduction (P > 0.05) was observed in the counts of S. mutans and L. acidophilus in PMMA without the nanoparticles exposed to UVA. CONCLUSIONS: PMMA resins incorporated with TiO(2)/SiO(2) nanoparticles showed strong antimicrobial activity against the cariogenic bacteria.