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Title: 0212 - Effectiveness of an Ultraviolet Light-emitting Diode (UV-LED) on Cariogenic Bacteria

Authors:

Shigeki Uchinuma (Presenter)
Tokyo Medical and Dental University

Yasushi Shimada, Tokyo Medical and Dental University
Khairul Matin, Tokyo Medical and Dental University
Yasunori Sumi, National Center for Geriatrics and Gerontology
Junji Tagami, Tokyo Medical and Dental University

Abstract:

Objectives: To determine the optimal UV dose from different wavelengths irradiating from a newly developed LED source for UV radiation generation device to inactivate cariogenic bacteria.

Methods: Streptococcus mutans MT8148 (S. mutans) and Streptococcus sobrinus 6715 (S. sobrinus) were cultured for18h in brain heart infusion broth (BHI). After washing, suspensions were prepared in PBS to an OD490=0.5 using a spectrophotometer. Aliquots of bacterial suspensions in a 96-well culture-plate were irradiated immediately by UV at 265nm (UV-C) and 310nm (UV-B) wavelengths and Blue-light (450nm; as control) for 2.5min or 5min separately. A LIVE/DEAD BacLight Bacterial Viability Kit (BacLight-kit) and a fluorescence-microscope (FM) were used to evaluate immediate bactericidal effects. Suspensions from all groups were serially diluted in PBS, plated on Mitis Salivarius agar plates and incubated anaerobically (48h). The number of colonies was counted and calculated as colony forming units (CFU)/ml. In addition, BHI was added to the suspensions at 3h after irradiation and incubated (37°C), and the absorbance was measured at every 3h up-until 15h at 490nm. CFU/ml were statistically analyzed (ANOVA, Bonferroni correction, p<0.05).

Results: An immediate bactericidal effect was observed on BacLight-kit stained FM images in case of UV-C. CFU/ml was significantly lower in the UV groups than non-treated group and Blue-light group regardless of the type of bacteria and irradiation time (p<0.05). The kinetic growth of S. mutans and S. sobrinus in BHI showed two different patterns. Non-treated group demonstrated exponential growth, whereas irradiation group (UV and Blue-light) had more linear growth.

Conclusions: The new UV-LED device appears to be a useful and handy device to control cariogenic bacteria as UV-B at a less powerful doses compared to UV-C have shown bactericidal effect considerably well. From the transition of absorbance, it was suggested that the long-term bactericidal effect of UV-LED on cariogenic bacteria depends on environmental conditions.

Student Presenter

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE

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