Lethal photosensitization of periodontal pathogens by a red-filtered Xenon lamp in vitro.
BACKGROUND
The ability of Helium-Neon (He-Ne) laser irradiation of a photosensitizer to induce localized phototoxic effects that kill periodontal pathogens is well documented and is termed photodynamic therapy (PDT).


OBJECTIVE
We investigated the potential of a conventional light source (red-filtered Xenon lamp) to activate toluidine blue O (TBO) in vitro and determined in vitro model parameters that may be used in future in vivo trials.


METHODS
Porphyromonas gingivalis 381 was used as the primary test bacterium.


RESULTS
Treatment with a 2.2 J/cm2 light dose and 50 micro g/ml TBO concentration resulted in a bacterial kill of 2.43 +/- 0.39 logs with the He-Ne laser control and 3.34 +/- 0.24 logs with the lamp, a near 10-fold increase (p = 0.028). Increases in light intensity produced significantly higher killing (p = 0.012) that plateaued at 25 mW/cm2. There was a linear relationship between light dose and bacterial killing (r2 = 0.916); as light dose was increased bacterial survival decreased. No such relationship was found for the drug concentrations tested. Addition of serum or blood at 50% v/v to the P. gingivalis suspension prior to irradiation diminished killing from approximately 5 logs to 3 logs at 10 J/cm2. When serum was washed off, killing returned to 5 logs for all species tested except Bacteroides forsythus (3.92 +/- 0.68 logs kill).


CONCLUSIONS
The data indicate that PDT utilizing a conventional light source is at least as effective as laser-induced treatment in vitro. Furthermore, PDT achieves significant bactericidal activity in the presence of serum and blood when used with the set parameters of 10 J/cm2, 100 mW/cm2 and 12.5 micro g/ml TBO.
Matevski
Donco
D
Faculty of Dentistry, University of Toronto, University of Toronto, Ontario, Canada.
Weersink
Robert
R
Tenenbaum
Howard C
HC
Wilson
Brian
B
Ellen
Richard P
RP
Lépine
Guylaine
G
D016976:Aggregatibacter actinomycetemcomitans / Q000187:drug effects; D001439:Bacteroides / Q000187:drug effects; D001769:Blood; D016967:Fusobacterium nucleatum / Q000187:drug effects; D006371:Helium; D006801:Humans; D053685:Laser Therapy; D009356:Neon; D010510:Periodontal Diseases / Q000382:microbiology; D010778:Photochemotherapy / Q000295:instrumentation / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D016966:Porphyromonas gingivalis / Q000187:drug effects*; D018713:Prevotella intermedia / Q000187:drug effects; D011829:Radiation Dosage; D014048:Tolonium Chloride / Q000627:therapeutic use*; D014978:Xenon
D017319:Photosensitizing Agents; D014048:Tolonium Chloride; D006371:Helium; D014978:Xenon; D009356:Neon