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Orthodontic treatment involves the use of apparatuses that impairs oral hygiene making patients susceptible to periodontal diseases and caries. To prevent increased antimicrobial resistance A-PDT has shown itself a feasible option. The aim of this investigation was to assess the efficiency of A-PDT employing 1,9-Dimethyl-Methylene Blue zinc chloride double salt - DMMB as a photosensitizing agent combined with red LED irradiation (λ640 ± 5 ηm) against oral biofilm of patients undertaking orthodontic treatment. Twenty-one patients agreed to participate. Four biofilm collections were carried out on brackets and gingiva around inferior central incisors; first was carried out before any treatment (Control); second followed five minutes of pre-irradiation, the third was immediately after the first AmPDT, and the last after a second AmPDT. Then, a microbiological routine for microorganism growth was carried out and, after 24-h, CFU counting was performed. There was significant difference between all groups. No significant difference was seen between Control and Photosensitizer and AmpDT1 and AmPDT2 groups. Significant differences were observed between Control and AmPDT1 and AmPDT2 groups, Photosensitizer and AmPDT1 and AmPDT2 groups. It was concluded that double AmPDT using DMBB in nano concentration and red LED was capable to meaningfully decrease the number of CFUs in orthodontic patients., Competing Interests: Declaration of Competing Interest None, (Copyright © 2023 Elsevier B.V. All rights reserved.)

Objective: To carry out a histological and morphometric analysis of the antimicrobial effect of Er:YAG laser irradiation combined with photodynamic therapy (PDT) on root canals infected with Enterococcus faecalis . Background: PDT and Er:YAG laser irradiation may be alternatives for effective endodontic disinfection but there are no data on the combination of these therapies. Materials and methods: Forty single-rooted bovine teeth had their roots contaminated with E. faecalis for 72 h. The teeth were randomly divided into four groups ( n  = 10): group 1, irrigation with 2.5% sodium hypochlorite (NaOCl); group 2, Er:YAG laser (λ2940 nm, 15 Hz, 100 mJ); group 3, PDT with 0.07% methylene blue as photosensitizer and laser irradiation (λ660 nm, power 40 mW, 5 min); and group 4, Er:YAG laser + PDT. After treatment, the teeth were examined by confocal laser scanning microscopy to verify bacterial viability, and morphometric analysis of the images was performed. Results: The PDT and Er:YAG + PDT treatments promoted the greatest reduction in bacteria among the proposed therapies, whereas 2.5% NaOCl was the least effective in bacterial elimination. A statistically significant difference ( p  < 0.05) was observed among the groups studied, except between the group combining Er:YAG and PDT and the group treated with PDT alone. Conclusions: PDT combined or not with Er:YAG laser was found to be more effective in root canal disinfection when compared with the other groups.

Antimicrobial Photodynamic Therapy (aPDT) is an alternative to conventional treatments of local infections such as the use of antibiotics, which may lead to the development of resistance. aPDT besides requiring the use of a photosensitiser also needs a light source do be carried out. In the search for efficient and low-cost procedure the use of multispectral polarized light (λ400-2000 nm) emerges as a possibility for the execution of aPDT. The use of a highly effective photosensitizer is also of great importance. 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt - DMMB is a potent phenothiazine derivative that presents high photodynamic action due to its high lipophilicity as well as a greater quantum yield of Singlet oxygen and phototoxicity when compared to other Photosensitizers. The aim of this study was to assess, In Vitro, the efficacy of aPDT on Staphylococcus aureus (ATCC 25923) using different concentrations of DMMB associated to a Polarized light source (Bioptron®, 40 mW, ᴓ = 15.8 cm 2 ) using different energy densities. Based on the IC 50 , 150 and 300 ng/mL of DMMB concentrations were chosen for this study. Twelve experimental groups were used: (Control, PLs, PSs and aPDTs). Serial dilutions (up to 10 -8 ) of the bacterial inoculum were used and the DMMB was added using the two previously determined concentrations. After 5 min of preincubation the dilutions of the inoculum were illuminated by the polarized light source. Subsequently, 100 μL of each dilution, in triplicate, were inoculated into Petri dishes containing TSA medium and incubated in a bacteriological oven at 37 °C for 24-h and quantification of UFCs was done. The results showed significant exponential reduction (p < .0001) of 99.93% (150 ng/mL + LP 10 J/cm 2 ) and 99.97% (300 ng/mL + LP 5 J/cm 2 ) the CFU counts in comparison to non-illuminated control. The results of this study allow to conclude that aPDT carried out with 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt-DMMB and a PL souce was efficacious on the reduction (99.97%), in vitro, of the bacterial counts of S. aureus., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The objective of this study was to evaluate, in vitro, the bactericidal effect of AmPDT on Staphylococcus aureus (ATCC 25923) using different concentrations (100, 50, 25, 12.5 and 6.25μg/mL) of phenothiazine compound combined with LED light (λ632±2nm) using varied energy densities (12, 9.6, 7.2, 4.8 and 2.4J/cm 2 ). The experiments were carried out in triplicate and the samples were divided into groups: Control, Irradiated (treated only with light at different energy densities), Photosensitizer (treated only in the presence of the dye), AmPDT (treatment with light associated with dye). Counts of the colony forming units and the data obtained were statistically analyzed (ANOVA, Tukey's test, p<0.05). The results showed no difference between irradiated and Control groups. However, using the photosensitizer alone caused significant increased cytotoxicity and consequent reduction on the CFU counts (12.5μg/mL (p<0.001), 25μg/mL, 50μg/mL and 100μg/mL (p<0.0001). When AmPDT was used significant inhibition above 70% were detected for all concentrations of the photosensitize (p<0.0001) except for 6.25μg/mL. The results indicate a dose-response dependent when the photosensitizer is used alone but not for the sole use of the light is used. It is concluded that, a single application of AmPDT, using energy density of 12J/cm 2 associated either to 12.5 (81.52%) or 25μg/mL (91.57%) resulted in higher in vitro inhibition of S. aureus., (Copyright © 2017 Elsevier B.V. All rights reserved.)