TiO₂ Nanotubes Added to Glass Ionomer Cement Affect S.mutans Metabolism

Objectives: This in vitro study evaluated the impact of different concentrations of TiO2 nanotubes (n-TiO2) incorporated to glass ionomer cement (GIC) on Streptococcus mutans(S. mutans) characteristics at cellular and molecular levels.
Methods: n-TiO2, synthesized by the alkaline method (20 nm in size), was added to Ketac Molar EasyMix® (n=6) at 3%, 5%, 7% by weight. S. mutans were cultured on GIC disks added or not with n-TiO2 for 1, 3 and 7 days and the following parameters assessed: Inhibition halo (mm); Cell viability – Live/Dead (CFU/ml); Cell morphology (SEM); and gene expression by real-time PCR (vicR, covR, gtfB, gtfC, and gtfD). Data were submitted to Kruskal-Wallis, repeated measured ANOVA or two-way ANOVA, followed by Tukey and Dunnet tests(α=0.05).
Results: Agar diffusion test showed that a higher antibacterial property was found for 5% n-TiO2 compared to 3% and 7% (p≤0.05) with no effect of time 1, 3 and 7 days. Cell number and viability were found to be significantly affected by n-TiO2. At 3% and 5%, n-TiO2 affected cell morphology and organization. Real-time PCR analysis demonstrated that n-TiO2 reduced the expression of covR when compared to the control group (p<0.05), with no effect of time, except for 3% n-TiO2 on vicR expression. Intra- and inter-group analysis revealed that TiO2 did not affect mRNA levels of gtfB, gtfC and gtfD(p>0.05).
Conclusions: The incorporation of n-TiO2 into GIC affected S. mutans biological behavior, including cell viability/morphology and gene expression. Therefore, n-TiO2 may be a promising strategy to improve GIC’s anticariogenic properties.