Streptococcus Mutans Biofilm Formation on Resin-based Composites including S-PRG Fillers

Objective: This study aimed to evaluate the release of fluoride and Streptococcus mutans biofilm formation on the surfaces of experimental resin-based composites (RBCs) including different fractions of surface pre-reacted glass ionomer filler particles. Method: Standardized specimens were prepared from five experimental RBCs with an identical BisGMA/TEGDMA matrix blend but different fractions of surface pre-reacted glass-ionomer (S-PRG) fillers (0/10/30/50/70% w/v). The RBCs were light-cured against mylar strips; 50% of the specimens received no further surface treatment (MYL) and the other 50% were polished to high gloss (POL). Surface roughness (SR), surface free energy (SFE) and the release of fluoride from the specimens` surfaces were determined. Streptococcus mutans biofilm formation (SMBF) was simulated for either 48 h or 120 h using a Drip-Flow Reactor; adherent viable biomass was assessed using a MTT-based assay. Statistical analysis was performed using two-way ANOVA and Student’s t-test (p<.05). Result: Significantly highest SR was identified for POL specimens prepared from the RBC with a filler weight of 70% (P=.005). For all specimens and surface treatments, polishing caused an increase in the polar contribution to SFE. For both MYL and POL specimens, increasing the S-PRG filler fraction caused an increased release of fluoride; POL specimens with a filler fraction of 50% and 70% released significantly more fluoride than MYL specimens. After 120 h, less fluoride was released in comparison to the 48 h data. Regarding SMBF, no significant differences were identified between MYL and POL specimens with identical filler fractions after 48 h; however, with increasing filler fractions, a tendency towards decreasing SMBF was observed. After 120 h, less SMBF was identified for POL specimens with a filler fraction of 30%, 50% and 70% in comparison to MYL specimens. Conclusion: High S-PRG filler fraction and surface treatment may positively influence Streptococcus mutans biofilm formation on fluoride-releasing RBCs.