Red fluorescence of dental biofilm as an indicator for assessing the efficacy of antimicrobials

Abstract

The study aimed to determine whether the red fluorescence (RF) of a dental microcosm biofilm as measured with quantitative light-induced fluorescence (QLF) technology is useful for assessing the efficacy of antimicrobials. Dental microcosm biofilms were formed on bovine enamel discs and grown under 0.3% sucrose challenge and treated with chlorhexidine (CHX) solutions at different concentrations (0.05%, 0.1%, and 0.5%) plus a negative control [sterile distilled water (DW)] twice daily for 7 days. The biofilms were photographed using a QLF-digital system to evaluate the RF by calculating the red/green ratio, and pH values of the medium were measured daily. After 7 days, the bacterial viability of the biofilm was assessed by measuring the counts of viable total bacteria and aciduric bacteria, and the percentage surface microhardness changes (%SHC) was evaluated. The RF and cariogenic properties were compared for the different concentrations of CHX, and their correlations were examined. The RF and its increase rate were much lower for CHX-treated biofilms than for DW-treated biofilms. The RF after 7 days of maturation decreased significantly with increasing CHX concentrations (p<0.001) and was from 31% (for 0.05% CHX) to 46% (for 0.5% CHX) lower than that of the DW group. Strong correlations were reported between the RF of the 7-day-maturation biofilms and cariogenic properties, such as the number of total bacteria (r=0.93), number of aciduric bacteria (r=0.97), supernatant pH (r=0.43), and %SHC (r=0.98). In conclusion, the RF of dental biofilms as measured with QLF technology can be used to nondestructively assess and monitor the effect of antimicrobials against biofilm.

Effects of short-time exposure of surface pre-reacted glass-ionomer eluate on dental microcosm biofilm

“…Furthermore, in accordance with the findings of Kim et al 18 , the R/G ratio in the present study increased considerably, exhibiting significant differences between the groups after maturation for more than three days (from the third day). These results are also consistent with previously published reports, which evaluated the effects of CHX in a microcosm biofilm model 19 . The positive control, 0.1% CHX, showed a slight increase in the R/G ratio from the third day, which is different from the results obtained for other groups.…”

“…Thus, red fluorescence corresponds to the cariogenicity of the biofilm and can be useful for examining the pathogenic levels. Consistent with the prior reports, the R/G ratio in this study increased with the maturation of the biofilm 12,19 . Furthermore, in accordance with the findings of Kim et al 18 , the R/G ratio in the present study increased considerably, exhibiting significant differences between the groups after maturation for more than three days (from the third day).…”

“…The red fluorescence of the biofilm is associated with the change in the microbial composition and periodontopathic pathogens in the biofilm, and the increase in maturity and pathogenicity can be determined by dental plaque emitting the red fluorescence 16 . Previous studies have shown that red fluorescence is proportional to the degree of maturation of the biofilm and strongly correlates with the number of bacteria and enamel demineralization [17][18][19] . Thus, red fluorescence corresponds to the cariogenicity of the biofilm and can be useful for examining the pathogenic levels.…”

“…Dental microcosm biofilms were formed using the model described in detail by Lee et al 19 Ethical approval for collecting human saliva was granted by the Ethics Committee of Yonsei Dental Hospital, Korea (IRB No. 02-2015-0051).…”

Antibacterial and antibiofilm activities of cinnamon essential oil nanoemulsion against multi-species oral biofilms

“…Biofilms were photographed once per day, immediately prior to treatment with the designated solution. QLF-D images were taken under the following conditions, while maintaining a consistent distance between the camera lens and each specimen of biofilm: shutter speed, 1/60 s; aperture value, 5.0; and ISO speed, 1600 27 . For fluorescence images, red and green values in the same area on each biofilm specimen were analyzed.…”