Purpose: To evaluate the effect of glass-ionomer cement (GIC) on gene expression (gtfC, gtfD, covR, and vicR) of Streptococcus mutans (S. mutans) biofilms at 2, 4 and 24 hours.
Methods: Six groups were tested according to the materials and time observation, as follows: ceramic (IPS Empress Esthetic), as the control group, and GIC (Ketac Molar Easymix); and time points of S. mutans biofilm formation (2, 4, and 24 hours). Round-shaped samples (10 x 2 mm) of each material were prepared according to the manufacturers' specifications. GIC discs were handled in a laminar flow hood under aseptic conditions and stored at 100% relative humidity at 37°C for 24 hours to complete setting reaction. The samples were placed in a 24-well plate and immersed in 1.5 ml BHI + 1% sucrose with an inoculum of S. mutans UA159 to allow biofilm growth during 2, 4, and 24 hours. Next, the samples were removed, vortexed and centrifuged to collect cell pellets (n=5) for each material and time point. Pellets were stored at -80°C. Then, RNA was purified using the RNeasy Mini Kit protocol. The RNA was converted in cDNA using iScript cDNA Synthesis according to the manufacturer's recommendations. Analysis of gtfC, gtfD, vicR, and covR expressions was performed using Step One Real-Time qPCR device with specific primers for each gene and the analysis normalized by 16S reference gene expression. Data from gtfC, gtfD, and vicR were analyzed by t-test to compare between groups while Mann-Whitney was used to analyze covR expression (α= 0.05).
Results: No significant differences at 2 and 4 hours between materials for all analyzed genes were noted. However, in the 24-hour period, a significant decrease in gtfC and vicR expressions were observed, while covR expression increased when GIC was compared to ceramic.
Clinical significance: The use of glass-ionomer cement decreased the virulence of S. mutans biofilms, which may imply a reduced bacterial cariogenic potential.
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