Evaluation of the Antibacterial Activity Against Streptococcus mutans and Solubility of Different Dental Luting Cements In Vitro

The aim of this in vitro study was to evaluate the antibacterial and solubility properties of four luting cements in artificial saliva at varying pH and clarify the composition by chemical analysis. Samples of bioceramic (C1), two resin-modified glass ionomer (C2 and C3), and zinc phosphate (C4) cements were stored on media with Streptococcus mutans and artificial saliva (pH 4.6 and pH 6.5). The disc diffusion method was used to evaluate antibacterial activity. In the solubility test, cement discs were stored in artificial saliva (pH 4.6 and pH 6.5) and distilled water (pH 7). After 48 and 120 hours, the solubility of the cement specimens was determined. Chemical analysis was performed by X-ray fluorescence. The growth inhibition zones of S. mutans induced by C4 were the largest in any pH values tested (p < 0.05). The solubility of C4 was significantly higher than the solubility of other cements. C2 had the smallest inhibition zones and was least soluble in all media during the observation period, but without significant differences. After 48 hours, the solubility of C4 was significantly higher at pH 4.6 compared to control. The solubility of the cements, excluding C2, was significantly higher after 120 hours at pH 6.5. A significant association was found between larger amount of zinc oxide in cement composition and a larger zone of inhibition. Lower solubility was associated with higher amounts of aluminium and silicon oxides in the cement. Thus, cement containing higher amounts of zinc oxides had the highest antibacterial activity. In the solubility test, cements were more soluble in acidic media than in neutral media, and lower solubility was detected in cements containing more aluminium and silicon oxides. In clinical practice, C1 or C3 may be suggested when there is a higher risk of caries due to more desirable combination of antibacterial activity and lower solubility, for a lower caries risk C2 might be suggested.