Abstract
Photoactivated disinfection has a strong local antimicrobial effect. In the field of dentistry it is an emerging adjunct to mechanical debridement during endodontic and periodontal treatment. In the present study, we investigate the effect of photoactivated disinfection using riboflavin as a photosensitizer and blue LED light for activation, and compare it to photoactivated disinfection with the widely used combination of toluidine blue O and red light. Riboflavin is highly biocompatible and can be activated with LED lamps at hand in the dental office. To date, no reports are available on the antimicrobial effect of photoactivated disinfection using riboflavin/blue light on oral microorganisms. Planktonic cultures of eight organisms frequently isolated from periodontal and/or endodontic lesions (Aggregatibacter actinomycetemcomitans, Candida albicans, Enterococcus faecalis, Escherischia coli, Lactobacillus paracasei, Porphyromonas gingivalis, Prevotella intermedia and Propionibacterium acnes) were subjected to photoactivated disinfection with riboflavin/blue light and toluidine blue O/red light, and survival rates were determined by CFU counts. Within the limited irradiation time of one minute, photoactivated disinfection with riboflavin/blue light only resulted in minor reductions in CFU counts, whereas full kills were achieved for all organisms when using toluidine blue O/red light. The black pigmented anaerobes P. gingivalis and P. intermedia were eradicated completely by riboflavin/blue light, but also by blue light treatment alone, suggesting that endogenous chromophores acted as photosensitizers in these bacteria. On the basis of our results, riboflavin cannot be recommended as a photosensitizer used for photoactivated disinfection of periodontal or endodontic infections.
Highlights
Photoactivated disinfection (PAD) has proven to have a strong antimicrobial effect on a range of different microorganisms including bacteria and fungi [1,2,3,4]
A. actinomycetemcomitans was cultivated on chocolate agar (Statens Serum Institut, Copenhagen, Denmark) in air enriched with 5% CO2; C. albicans, E. faecalis, E. coli and L. paracasei were grown on blood agar (Statens Serum Institut, Copenhagen, Denmark) under aerobic conditions; P. acnes was grown on blood agar under anaerobic conditions; P. gingivalis and P
A. actinomycetemcomitans, P. gingivalis, P. intermedia and P. acnes were cultivated in plaque medium [38]; C. albicans, E. faecalis, E. coli and L. paracasei were grown in tryptic soy broth (Scharlab, Barcelona, Spain)
Summary
Photoactivated disinfection (PAD) has proven to have a strong antimicrobial effect on a range of different microorganisms including bacteria and fungi [1,2,3,4]. Comparison of PAD with Riboflavin and Toluidine Blue O a photosensitizer (PS) by light of an appropriate wavelength, which generates reactive oxygen species (ROS) when molecular oxygen is present. The triplet state PS may react further via one or both of two pathways that lead to microbial killing: In type I reactions, triplet state PS reacts directly with microbial constituents by electron transfer. This produces radical ions which react with oxygen to generate ROS that can be detrimental to microbial membrane integrity [5, 6]. Singlet oxygen causes oxidation of microbial constituents such as lipids, proteins and nucleic acids
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