ABSTRACT
PURPOSE: To investigate whether photomechanical waves generated by lasers can increase the permeability of a biofilm of the oral pathogen Actinomyces viscosus. METHODS: Biofilms of Actinomyces viscosus were formed on bovine enamel surfaces. The photomechanical wave was generated by ablation of a target with a Q-switched ruby laser and launched into the biofilm in the presence of 50 microg/ml methylene blue. The penetration depth of methylene blue was measured by confocal scanning laser microscopy. Also, the exposed biofilms were irradiated with light at 666 nm. After illumination, adherent bacteria were scraped and spread over the surfaces of blood agar plates. Survival fractions were calculated by counting bacterial colonies. RESULTS: Confocal scanning laser microscopy revealed that a single photomechanical wave was sufficient to induce a 75% increase in the penetration depth of methylene blue into the biofilm. This significantly increased the concentration of methylene blue in the biofilm enabling its photodestruction. CONCLUSIONS: Photomechanical waves provide a potentially powerful tool for drug delivery that might be utilized for treatment of microbial infections.
Subject(s)
Actinomyces viscosus/radiation effects , Anti-Bacterial Agents/administration & dosage , Biofilms , Actinomyces viscosus/drug effects , Animals , Cattle , Light , Microscopy, Confocal/methodsABSTRACT
Suspensions of Streptococcus mutans, S. sobrinus, Lactobacillus casei and Actinomyces viscosus were exposed to light from a gallium aluminium arsenide laser in the presence of aluminium disulphonated phthalocyanine and the numbers of survivors determined. Exposure to the laser light in the absence of the dye, or the dye in the absence of the laser light, had no significant effect on the viability of the organisms. However, a light-dose-related decrease in the viable count of all four target organisms was found on exposure to the laser light in the presence of the dye. The kills attributable to lethal photosensitization amounted to approximately 10(6) CFU in the case of each organisms. As appreciable kills were achieved within clinically convenient exposure times (30-90 s), these results imply that lethal photosensitization may be a useful technique for eliminating bacteria from carious lesions prior to restoration.
Subject(s)
Bacteria, Anaerobic/radiation effects , Lasers , Actinomyces viscosus/drug effects , Actinomyces viscosus/radiation effects , Arsenicals , Bacteria, Anaerobic/drug effects , Colony Count, Microbial , Dose-Response Relationship, Drug , Dose-Response Relationship, Radiation , Gallium , Indoles/pharmacology , Lacticaseibacillus casei/drug effects , Lacticaseibacillus casei/radiation effects , Microbial Sensitivity Tests , Organometallic Compounds/pharmacology , Photosensitizing Agents/pharmacology , Streptococcus mutans/drug effects , Streptococcus mutans/radiation effects , Streptococcus sobrinus/drug effects , Streptococcus sobrinus/radiation effectsABSTRACT
Suspensions of the cariogenic bacteria Streptococcus mutans, S. sobrinus, Lactobacillus casei and Actinomyces viscosus were exposed to light from a 7.3-mW helium-neon laser in the presence of toluidine blue O. A substantial killing rate (c. 10(6) cfu) of all four species was achieved with a dye concentration of 50 micrograms/ml and a light energy dose of 33.6 J/cm2. This was achieved in 60 s, an exposure time that is clinically acceptable. Exposure to laser light in the absence of the dye did not significantly affect the viability of any of the organisms. This approach may be useful in dentistry to sterilise a carious lesion prior to its repair.
