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, Fusobacterium 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.

Blue LED inhibits the growth of Porphyromonas gingivalis by suppressing the expression of genes associated with DNA replication and cell division

“…The red LED irradiation (135 J/cm 2 ) did not lead to any differences in the bacterial cells compared to the non‐irradiated control in terms of their growth. In contrast, blue LED irradiation (135 J/cm 2 ) delayed the growth of P. gingivalis , which was in agreement with the results of previous studies 9, 20–23, 28, 29. However, the molecular mechanisms underlying the effects of blue light/LED exposure on bacterial growth were unclear with regard to whether blue light/LED light actually kills bacteria or only inhibits their growth.…”

“…In addition, there have been many reports about the effects of LED on bacteria. Red light or near infrared light was reported to exert no antimicrobial effects 18–20. In contrast, blue light has been reported to possess a bactericidal effect; the delivery of blue light (representing 15–58.8 J/cm 2 energy density) is sufficient to reduce the viability of bacteria such as H. pylori 9, methicillin‐resistant Staphylococcus aureus 21, Pseudomonas aeruginosa , and S. aureus 22.…”

“…In contrast, blue light has been reported to possess a bactericidal effect; the delivery of blue light (representing 15–58.8 J/cm 2 energy density) is sufficient to reduce the viability of bacteria such as H. pylori 9, methicillin‐resistant Staphylococcus aureus 21, Pseudomonas aeruginosa , and S. aureus 22. Regarding periodontal pathogens, blue light/blue LED (4.2–94 J/cm 2 ) reduce the survival rates of P. gingivalis 20, Fusobacterium nucleatum 20, Prevotella internedia 23, and Prevotella nigrescens 23. Upon the blue LED irradiation, it has been speculated that endogeneous prophyrin produced by bacteria is excited and leads to photodynamic reaction through the singlet oxygen production, thus resulting in bacterial killing 24.…”

Antimicrobial effect of photodynamic therapy using high‐power blue light‐emitting diode and red‐dye agent on Porphyromonas gingivalis

“…BL at a wavelength of 405 nm (15 J/cm 2 ) achieved reduction rates of 95.1% and nearly 90% for Pseudomonas aeruginosa and S. aureus , respectively . Regarding periodontal pathogens, BL at 94 J/cm 2 (3 min) reduced the survival rates of P. gingivalis and Fusobacterium nucleatum by 90% and 40%, respectively . Moreover, BL irradiation at 4.2 J/cm 2 (1 min) resulted in complete killing of Prevotella intermedia and Prevotella nigrescens , and irradiation at 42 J/cm 2 (10 min) reduced P. gingivalis by 98.5% .…”

“…On BL irradiation, it has been speculated that endogenous porphyrin produced by bacteria is excited, leading to a photodynamic reaction through singlet oxygen production, resulting in an antimicrobial effect . In contrast, some in‐vitro studies reported that red light or near‐infrared light exerted no antibacterial effect .…”