Modification of glass-ionomer cement properties by quaternized chitosan-coated nanoparticles.

Glass ionomers (GICs), because of their qualities, are in a good position to be modified to resist masticatory stresses as permanent posterior restoration and prevent recurrent caries. The purpose of the present study was to evaluate the effect of adding quaternized chitosan-coated mesoporous silica nanoparticles (HTCC@MSNs) to conventional GIC on its mechanical properties, antimicrobial activity and fluoride release and the effect of 1- and 3-month water aging on the studied properties. HTCC@MSNs was synthesized, added to commercially available conventional GIC at 1%, 3%, and 5% by weight forming three experimental groups and compared with plain GIC as a control group. Flexural strength, modulus, Vickers microhardness and wear volumes were evaluated. Antibacterial activity was tested against Streptococcus mutans and fluoride release in de-ionized water was measured. All properties were evaluated before and after one- and three-month aging (n = 10 specimens per test/per time). Two-way ANOVA was used for statistical analysis. Characterization confirmed successful preparation of HTCC@MSNs. The flexural strength, modulus, hardness and wear resistance of the GICs improved significantly by adding 1-3% HTCC@MSNs, while 5% HTCC@MSNs group showed no significant difference compared to control group. Bacterial inhibition zones and fluoride release increased proportionally to the amount of filler added. Mechanical properties were improved by artificial aging. Fluoride release values, and bacterial inhibition zones decreased with aging for all groups. HTCC@MSNs as a filler with the optimized proportion provides strengthening and antibacterial effect. In addition, aging is an important factor to be considered in evaluating experimental fillers.