Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum

Abstract

treatment with antimicrobial chemotherapeutic agents, alternative approaches such as lethal

photosensitization are being used. The aim of this study was to evaluate the effect of visible light

and laser beam radiation in conjugation with three different photosensitizers on the survival of two

main periodontopathogenic bacteria including Porphyromonas gingivalis and Fusobacterium nucleatum

in different exposure periods.

Materials and Methods: In this in vitro prospective study, strains of P. gingivalis and F.

nucleatum were exposed to visible light at wavelengths of 440 nm and diode laser light,

Gallium-Arsenide, at wavelength of 830 nm in the presence of a photosensitizer (erythrosine,

curcuma, or hydrogen peroxide). They were exposed 1-5 min to each light. Each experiment

was repeated 3 times for each strain of bacteria. Data were analyzed by two-ways ANOVA

and least significant difference post-hoc tests. P < 0.05 was considered as significant. After 4

days the colonies were counted.

Results: Viability of P. gingivalis was reduced 10% and 20% subsequent to exposure to visible light

and diode laser, respectively. The values were 65% and 75% for F. nucleatum in a period of 5-min,

respectively. Exposure to visible light or laser beam in conjugation with the photosensitizers

suspension caused signifi cant reduction in the number of P. gingivalis in duration of 5-min,

suggesting a synergic phototoxic effect. However, the survival rate of F. nucleatum following

the exposure to laser with hydrogen peroxide, erythrosine and rhizome of Curcuma longa

(curcumin) after 5-min was 10%, 20% and 90% respectively.

Conclusion: Within the limitations of this study, the synergic phototoxic effect of visible light in

combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic

phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on

F. nucleatum was not shown.

Key Words: Laser therapy, periodontitis, pathogenic bacteria, phototherapy