In vitro-activity of photoactivated disinfection using LED light in the blue spectrum against periodontopathogens

Objectives: Light in the blue spectrum is well known to cure composite materials based on camphorquinone as photoinitiator. This in vitro-study was aimed to analyze a potential antimicrobial activity when combined with riboflavin as a photosensitizer.
Methods: Photoactivated disinfection (PAD) using an LED lamp emitting in the blue spectrum for 30 s (PAD30) and 60 s (PAD60) after application of 0.1% riboflavin was compared with a LED lamp emitting in the red spectrum with the respective photosensitizer (PADred). Killing activity was analyzed against planktonic 14 single species and a 12-species mixture with and without 25% serum. In addition, reduction of viable bacterial counts in single species and a 12-species biofilm was measured after PAD.
Results: Gram-positive bacteria were less sensitive to PAD30 and PAD60 than Gram-negatives. PAD60 decreased the counts by more than 3 log₁₀ cfu in two of five Gram-positive and six of nine Gram-negative strains, the total viable counts of the mixture were reduced by 1.04 ± 0.46 log₁₀ cfu. In the presence of 25% serum PAD60 did not reduce the cfu counts by more than 3 log₁₀ cfu; a decrease by more than 2 log₁₀ cfu was only found in tests with Porphyromonas gingivalis ATCC 33277. PADred killed all included strains except for the 12-species mixture and Eubacterium nodatum ATCC 33099. PAD60 reduced the counts in P. gingivalis biofilms by 2 – 3 log₁₀ cfu, however there was no activity of PAD60 and PADred on the multi-species biofilm.
Conclusions: PAD using LED emitting in the blue spectrum combined with riboflavin is active against planktonic periodontopathic microbial species even in the presence of serum and in single-species biofilms. An elimination of multi-species biofilms appears to be impossible thus underlining the importance of mechanical biofilm removal prior to treatment.