Synergic phototoxic effect of visible light or Gallium-Arsenide laser in the presence of different photo-sensitizers on Porphyromonas gingivalis and Fusobacterium nucleatum.
BACKGROUND
According to the development of resistant strains of pathogenic bacteria following 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.


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 significant 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.


CONCLUSIONS
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.
Oral and Maxillofacial Diseases Research Center and Department of Periodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
Habibollah
H
Ghanbari
Torabinejad Dental Research Center and Departments of Endodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
Seyed Amir
SA
Mousavi
Oral and Maxillofacial Diseases Research Center and Department of Periodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
Ali
A
Forouzanfar
Oral and Maxillofacial Diseases Research Center and Department of Periodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
Mahdi
M
Zakeri
Dental Research Center, Department of Orthodontics, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
Hooman
H
Shafaee
Dental Implant Research Center and Oral and Maxillofacial Surgery, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran.
Shirin
S
Shahnaseri
Laser therapy; pathogenic bacteria; periodontitis; phototherapy