Suppression of Streptococcus mutans Biofilm Formation and Gene Expression by PRG Barrier Coat: A Molecular and Microscopic Study for Preventing Dental Caries.

Purpose: This study aimed to investigate the inhibitory effect of a PRG Barrier Coat on biofilm formation and structure by Streptococcus mutans and propose an effective method for preventing dental caries.

Materials and methods: Streptococcus mutans MT8148 biofilms were obtained from hydroxyapatite disks with and with- out a PRG Barrier Coat. Scanning electron microscopy (SEM) was used to observe the 12- and 24-h-cultured biofilms, while reverse-transcription polymerase chain reaction (qRT-PCR) was used to quantify caries-related genes. Biofilm adhe- sion assessments were performed on glass. Statistical analysis was performed using a two-sample t-test.

Results: A statistically significant difference in Streptococcus mutans biofilm adhesion rate was observed between the con- trol and PRG Barrier Coat-coated samples (p < 0.01). However, there was no statistically significant difference in total bacter- ial count or biofilm volume (p > 0.05). SEM revealed that the PRG Barrier Coat inhibited biofilm formation by Streptococcus mutans. Real-time RT-PCR revealed that the material restricted the expression of genes associated with caries-related bio- film formation. However, the suppression of gtfD and dexB differed from that of other genes.

Conclusion: PRG Barrier Coat suppressed biofilm formation by Streptococcus mutans by inhibiting the expression of in- soluble glucan synthase, which is associated with primary biofilm formation. The material also affected gene expression and altered the biofilm structure. Tooth surface-coating materials, such as PRG Barrier Coat, may improve caries preven- tion in dental practice.