Phototoxic Effect of Visible Light on Porphyromonas gingivalis and Fusobacterium nucleatum: An In Vitro Study^¶†

Abstract

The antibacterial effect of visible light irradiation combined with photosensitizers has been reported. The objective of this was to test the effect of visible light irradiation without photosensitizers on the viability of oral microorganisms. Strains of Porphyromonas gingivalis, Fusobacteriurm nucleatum, Streptococcus mutans and Streptococcus faecalis in suspension or grown on agar were exposed to visible light at wavelengths of 400–500 nm. These wavelengths are used to photopolymerize composite resins widely used for dental restoration. Three photocuring light sources, quartz‐tungsten‐halogen lamp, light‐emitting diode and plasma‐arc, at power densities between 260 and 1300 mW/cm2 were used for up to 3 min. Bacterial samples were also exposed to a near‐infrared diode laser (wavelength, 830 nm), using identical irradiation parameters for comparison. The results show that blue light sources exert a phototoxic effect on P. gingivalis and F. nucleatum. The minimal inhibitory dose for P. gingivalis and F. nucleatum was 16–62 J/cm2, a value significantly lower than that for S. mutans and S. faecalis (159–212 J/cm2). Near‐infrared diode laser irradiation did not affect any of the bacteria tested. Our results suggest that visible light sources without exogenous photosensitizers have a phototoxic effect mainly on Gram‐negative periodontal pathogens.

Zinc enhances the phototoxic effect of blue light against malodour-producing bacteria in an experimental oral biofilm

“…photodynamic treatment) has been reported in the literature (Wilson, 1994;Henry et al, 1995Henry et al, , 1996Konig et al, 2000;Soukos et al, 2005), and it has been suggested that this effect is mediated through the production of ROS (Gourmelon et al, 1994). This hypothesis is further supported by the observation that obligate anaerobic oral bacteria (pigmented and non-pigmented) are more susceptible to blue light exposure treatment than facultative ones (Feuerstein et al, 2004;Sterer & Feuerstein, 2005). Various studies have reported that using the colourant erythrosine B as a photosensitizer enhances the antimicrobial properties of blue light from light-emitting diode (LED) or halogen light sources (De Lucca et al, 2012;Lee et al, 2012).…”

Rose bengal uptake by E. faecalis and F. nucleatum and light-mediated antibacterial activity measured by flow cytometry

“…Also, light irradiation alone (240 s) had no effect on E. faecalis but reduced F. nucleatum viability by approximately 10%. This strain was shown to possess several intracellular compounds such as cytochromes or flavins, which may have acted as endogenous photosensitizers [38][39][40].…”

A Possible Mechanism for the Bactericidal Effect of Visible Light

“…For example Feursteinet et al,1) showed that broadband blue light sources at 400-500nm exert a phototoxic effect on P. gingivalis and F. nucleatum, and Henry et al,2) demonstrated that low fluencies of argon laser irradiation (488-514 nm) exert a phototoxic effect on Porphyromonas and Prevotella spp., which are both Gram negative anaerobic bacteria that produce porphyrins. Oral black-pigmented bacteria (BPB) in pure cultures and in dental plaque samples were killed by 4.2 J/cm 2 blue light, whereas P. melaninogenica required 21 J/cm 2 .…”