Effects of Surface Prereacted Glass on Saliva-Derived Polymicrobial Biofilms in an Active Attachment Biofilm Model

Abstract

Bioactive restorative materials are being developed to either influence the de/remineralization balance of the dental hard tissues locally or to release components that interact with the oral microbiota. Surface prereacted glass (S-PRG, Shofu, Japan) is a material that may influence both processes. S-PRG releases fluoride, which can interact with the de/remineralization process, and a range of other compounds that may influence the oral microbiota. In the current study, several experiments were performed to investigate the potential of S-PRG to influence both the growth and lactic acid production of saliva-derived polymicrobial biofilms. Biofilm formation was studied using the Amsterdam Active Attachment model. An eluate of the S-PRG particles was tested by adding it to the growth medium or by exposing the biofilms to it for 1 h. The effect of S-PRG particles was tested by adding the particles to the growth medium. The current experiments showed that the presence of S-PRG eluate in the medium influenced biofilm growth and lactic acid production even at low concentrations. The composition of the biofilms changed in the presence of S-PRG eluate, even at concentrations of S-PRG eluate at which biofilm viability was not affected. Treatment of developing biofilms with S-PRG eluate did neither show an effect on biofilm viability nor on lactic acid production. The addition of S-PRG particles to the growth medium resulted in both a lower biofilm viability and lower lactic acid production, indicating that the release of ions from the particles was fast enough to influence biofilm formation. From the current experiments, it can be concluded that S-PRG has the potential to influence biofilm growth, but the presence of the released ions during biofilm formation is required to show an effect.

Keywords: Antimicrobial agents; Biofilms; Microbiology; Next-generation sequencing; Surface prereacted glass.

Fig. 1

Effect of repeated treatment of developing biofilms with S-PRG eluent on biofilm viability (a) and lactic acid production (b) versus time points (h) of the treatments. Groups (n = 6) were not statistically different from each other.

Fig. 2

Effect of presence of diluted S-PRG eluent during growth on biofilm viability (a) and lactic acid production (b). Bars show the average and standard deviation of the mean. Groups (n = 4) with the same letter are not statistically significantly different to each other.

Fig. 3

Principal component analysis of the biofilm microbiota profiles formed in the presence of different amounts of S-PRG eluent. At 12.5% and 50% of S-PRG eluent, the composition was clearly different from the other groups (a). PCA with the lower S-PRG concentrations only shows the differences in these groups: also at lower levels (with no effect on biofilm viability), differences in composition can be observed (b).

Fig. 4

Effect of adding S-PRG particles to the growth medium on biofilm viability (a) and lactic acid production (b). Biofilm formation was started with different inoculation ratios of saliva versus growth medium. Bars show the average and standard deviation of the mean. Groups (n = 4) with the same letter are not statistically significant different.

Fig. 5

Biofilm viability (a) and lactic acid production (b) of biofilms that were grown 24 h in the absence of S-PRG particles and subsequently 24 h in the presence of S-PRG particles. Biofilm formation was started at two different inoculation ratios (1:50 and 1:5,000). S-PRG particles (0.8 μm) were added after 24 h at two different ratios (1:50 and 1:250). Bars show the average and standard deviation of the mean. Groups (n = 4) with the same letters are not statistically significantly different.