The change of Streptococcus mutans biofilm inhibition effect of composite resins containing bioactive glass-ursolic acid after 6 month water storage

Abstract

1. Objective

The aim of this study was to investigate the S.mutans biofilm formation on composite

surface containing bioactive glass and ursolic acid when exposed to distilled water for 6

months compared with fresh antibacterial composite resin specimen.

2. Materials and methods

Four experimental groups and one control group were prepared : Conventional

composite (10%wt OX50 silica nanofiller instead of BAG) as control, BAG filler group

(BAG), BAG filler coated with UA group (UA BAG), UA added to resin matrix (BAG+UA

Monomer), and UA added to BAG and resin matrix (UA BAG+UA Monomer). All

specimens were stored in distilled water for 6 months (the aged resin group). After

sterilization with ethylene oxide gas, biofilm assay was performed again on all five groups.

The specimens for the aged resin group were fabricated on the previous study by Kim

(Kim B, 2013), and re-used for this study.

For biofilm assay, S. mutans was incubated for 24 hours with each composite resin disk

specimen in a biofilm medium with either glucose or sucrose in the presence or absence of

a salivary coating. The adherent bacteria were quantified after sonication of the specimen

by counting the colony forming units of viable bacteria.

Calcium and fluoride ions concentration released from new and aged specimens were

analyzed quantitatively by using Ion Chromatography (IC).

Five disk specimens of each group were immersed and stored in 5 ml distilled water for

24 hours. The measurement of ion release was carried out by using the IC on 1-day

interval for 7 days.The t-test for variable CFU was used for biofilm assay to analyze statistical significance between new and aged groups. To analyze the effect of composite composition on the biofilm formation, one-way analysis of variance (ANOVA) followed by a multiplecomparison Tukey test was performed. The amount of calcium and fluoride ion release between old resin groups and new resin groups was compared using t- test at a 5% level of significance.

3. Result

When glucose was given as a carbohydrate source, there was no significant difference

between new and aged resin under saliva non-coating condition. In new resins, the CFU

values of all experimental groups were significantly lower than control group. However, in

aged resin, only the BAG + UA Monomer group showed significantly lower CFU value than

control group. In saliva coating condition, the CFU value of all aged resin groups

significantly increased compared to all new resin groups. In the new resin groups, the CFU

value of all experimental groups was significantly lower than control. However, there was

no significant difference between control and BAG group on aged resin.

When sucrose was given as a carbohydrate source, under salivary non-coating condition,

CFU value of aged resin significantly increased more than new resin on all experimental

groups except in the control group. In the new resin groups, the CFU value of BAG + UA

Monomer, UA BAG + UA Monomer group was significantly lower than control. However,

there was no significant difference between all groups in aged resin groups. In saliva

coating condition, the CFU value of BAG + UA monomer, UA BAG + UA Monomer group

was significantly lower than control group in aged resin and new resin.

On both calcium and fluoride, new resin showed higher amount of ion release than aged

resin. A significant difference was shown on fluoride ion release all day, and new resin

showed significantly higher release of calcium ion on the 1st, 5th day. On both calcium and

fluoride, a significantly high concentration of ion release was shown on the 1st day in new

resin specimen. The amount of ion release showed significant decrease on the 2nd day, but

increased on the 3rd day.

4. Conclusion

In glucose source, experimental new composites containing BAG and/or UA showed

significant reduction of biofilm formation by S. mutans. However, after storage in distilled

water for 6 months, experimental composites containing BAG showed decreased biofilm

inhibition effect. The composites with UA added to the monomer still showed significant

inhibition effect of the biofilm formation by S. mutans even after storage in distilled water.

In sucrose source, the new composites of UA Monomer group showed significant

antibacterial effect under any salivary treatment. After storage in distilled water for 6

months, the biofilm formation was affected by salivary treatment. In Saliva non-coating

groups, there were no significant difference in all groups, and in saliva coating groups, BAG

+ UA Monomer and UA BAG + UA Monomer groups showed lower CFU values.

Following the results of this experiment, it can be concluded that the UA incorporated in

monomer was more effective method to keep the antibacterial effect in any biofilm

formation condition after 6 month water storage condition.

Within the limitation of this experiment, this result indicates that UA inhibits biofilm

formation by S. mutans and suggests that UA has potential for use as an effective

antibacterial agent to prevent dental caries in the future.