Novel Dental Technologies for Antibacterial Blue Light Irradiation

Objectives: Periodontal biofilms may be a source for dissemination and development of systemic infections by pathogenic species that have been detected in high prevalence and levels in the periodontal microbiota. The aim is to develop novel technologies to study photodisinfection in pathogens and to assess the effects of bacteria species, strain, wavelength and exposure time/energy delivered.
Methods: A LED array was manufactured using light emitting diodes (LEDs). The array was designed to fit intimately into a 96-well microplate and consisted of 5 channels of different wavelengths (375nm, 395nm, 405nm, 420nm and 450nm) calibrated to an irradiance of 350mW/cm². Heating was managed using heat sinks and directional air-flow through the irradiation compartment. Blue light irradiation efficacy was assessed in overnight planktonic broth cultures of 5 strains of Staphylococcus aureus and Pseudomonas aeruginosa in black 96-well plates at standardised optical density (OD₆₀₀ = 0.01). Following seeding, the broth cultures were immediately irradiated for exposure times of 5-20minutes. After 20h, OD₆₀₀ was determined using a microplate reader. Multifactorial analysis of variance and post-hoc Tukey tests (P=0.05) were used to identify significant differences.
Results: Antimicrobial effects were wavelength, exposure time, bacteria species and strain dependent (P<0.05). Generally, a significant decrease that was comparable to the optical density of sterile broth was measured at 395nm and 405nm for 20 minute exposures in both species and most strains (P<0.05). Shorter exposure times decreased the efficacy of irradiation in a dose dependent manner with 5 minute exposures resulting in non-significant differences between the non irradiated control in most cases (P>0.05). Reduced blue light efficacy even after 20minute exposure was measured (<20% reduction) in one strain of Pseudomonas aeruginosa (4135).
Conclusions: Bacteria specific and strain specific irradiation parameters may allow targeted photon delivery for optimised antibacterial effects and has the potential to advance as a disruptive technology for decontamination.