This study evaluated the antibacterial effects of short-time exposure of surface pre-reacted glassionomer (S-PRG) eluate on oral microcosm biofilm. Biofilms were treated with an S-PRG eluate at different concentrations (25%, 50%, and 100%), distilled water (DW), and 0.1% chlorhexidine (CHX) twice a day for 5 min repeatedly. After 7 days, the total and aciduric bacterial counts and biofilm dry weights were measured. An image analysis program calculated the red/green (R/G) ratios in the biofilm autofluorescence images. Microscopic analyses quantified the biofilm thickness and live/dead cell ratio and determined morphological changes in the biofilm. Bacterial counts and dry weights were not significantly different in the DW group for all S-PRG eluate concentrations. An increasing trend in the R/G ratio for 7 days biofilm treatment was observed for the S-PRG eluate and the DW groups. Furthermore, the live/dead cell ratios in the biofilm and the biofilm thickness of the S-PRG eluate groups were similar to those of the DW group. The bacteria morphology inside the biofilm changed only in the CHX group. Short-time S-PRG eluate treatment showed no significant antibacterial and antibiofilm effects. These results indicated that limited biofilm formation inhibition can be obtained by using only the S-PRG eluate. Dental caries is a major oral disorder caused by the pathogenic bacteria inhabiting complex microbial communities known as biofilms 1. Intraoral biofilms increase the resistance against planktonic bacteria and make it difficult for foreign substances to penetrate the extracellular matrix that forms a thick physical layer via an acquired pellicle stage 2. Physical interventions including toothbrushing and the use of dental chemicals containing effective antibacterial components have been proposed as self-management methods for removing these oral biofilms 3. Various antibacterial active ingredients are currently under development, and numerous studies have evaluated their effectiveness in preventing dental caries by examining the antibacterial and anticariogenic effects. Various recent studies have reported the remineralization and antibacterial activities of dental restorative materials constructed using a pre-reacted glass-ionomer (PRG) technology in combination with polymers 4. Surface pre-reacted glass-ionomer (S-PRG) filler is a material treated with a siliceous hydrogel that is formed via an acid-base reaction between fluoroboroaluminosilicate glass and polyacrylic acid.

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