Phototoxic effect of blue light on the planktonic and biofilm state of anaerobic periodontal pathogens

Abstract

PurposeThe purpose of this study was to compare the phototoxic effects of blue light exposure on periodontal pathogens in both planktonic and biofilm cultures.MethodsStrains of Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, and Porphyromonas gingivalis, in planktonic or biofilm states, were exposed to visible light at wavelengths of 400.520 nm. A quartz-tungsten-halogen lamp at a power density of 500 mW/cm2 was used for the light source. Each sample was exposed to 15, 30, 60, 90, or 120 seconds of each bacterial strain in the planktonic or biofilm state. Confocal scanning laser microscopy (CSLM) was used to observe the distribution of live/dead bacterial cells in biofilms. After light exposure, the bacterial killing rates were calculated from colony forming unit (CFU) counts.ResultsCLSM images that were obtained from biofilms showed a mixture of dead and live bacterial cells extending to a depth of 30-45 µm. Obvious differences in the live-to-dead bacterial cell ratio were found in P. gingivalis biofilm according to light exposure time. In the planktonic state, almost all bacteria were killed with 60 seconds of light exposure to F. nucleatum (99.1%) and with 15 seconds to P. gingivalis (100%). In the biofilm state, however, only the CFU of P. gingivalis demonstrated a decreasing tendency with increasing light exposure time, and there was a lower efficacy of phototoxicity to P. gingivalis as biofilm than in the planktonic state.ConclusionsBlue light exposure using a dental halogen curing unit is effective in reducing periodontal pathogens in the planktonic state. It is recommended that an adjunctive exogenous photosensitizer be used and that pathogens be exposed to visible light for clinical antimicrobial periodontal therapy.

Effect of Antimicrobial Photodynamic Therapy as an Adjunct to Nonsurgical Treatment of Deep Periodontal Pockets: A Clinical Study

“…It is supported by in vitro studies that report effective killing of periodontal microbes in planktonic and biofilm samples. 16,17 Therefore, the aim of the present study was to evaluate the additional benefit of aPDT, if any, in addition to SRP alone. At the baseline examination, there was no statistically significant difference between the two groups in any of the recorded parameters i.e.…”

The effect of chlorhexidine mouth wash and visible blue light on Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis of patients with chronic periodontitis ( an in–vitro study)

“…suggested that increases in temperature could damage bacteria after exposure to blue light. Oxidative stress occurs with reactive oxygen species such as superoxide anion, hydrogen peroxide, and hydroxyl radicals that damage proteins, DNA, lipid, and the cell membrane 32 .Hyun-Hwa Song et al (2013) showed that blue light exposure is available to reduce periodontal pathogens in the planktonic state. However, periodontal pathogens in the intraoral environment exist in a biofilm state.…”

“…And found a Little phototoxic effect even in the biofilm states of A. actinomycetemcomitans and F. nucleatum. Therefore he recommended that an adjunctive exogenous photosensitizer (e.g., methylene blue, toluidine blue O, erythrosine) be used when visible light exposure is used for antimicrobial periodontal therapy 17 .…”

“…However, some bacteria do not require exogenous photosensitizers. Black-pigmented bacteria (BPB) indicate the use of an endogenous photosensitizer such as porphyrins, we hypothesize that killing effect is a result of light excitation of their endogenous porphyrins [17][18][19] .Although classified as anaerobes, the BPB species found in the oral cavity can tolerate low concentrations of oxygen, comparable to those levels in untreated human periodontal pockets. These small amounts of oxygen render periodontal diseases susceptible to Photodynamic therapy (PDT)…”

The antimicrobial effect of blue light: What are behind?

“…25,27,28 Other studies demonstrated that aBL did not cause significant damages to host cells and did not impair wound healing. 18,26,28,34,39,40 In this issue of Virulence, Fila et al 22 investigated the effectiveness of aBL inactivation of Pseudomonas aeruginosa using a panel of wide types and clinical strains, including multidrug-resistant and extensively drug-resistant strains. In agreement of previous studies, the authors found that aBL exerted significant antimicrobial effect on all Pseudomonas aeruginosa strains tested, resulting in 5.2-to 8-log 10 reduction of colony forming units (CFU).…”