Exploring different photodynamic therapy parameters to optimize elimination of Enterococcus faecalis planktonic forms

Publication date: Available online 29 March 2018
Source:Photodiagnosis and Photodynamic Therapy
Author(s): Janir Alves Soares, Suelleng Maria Cunha Santos Soares, Rudys Rodolfo de Jesus Tavarez, Claudia de Castro Rizzi, Silvana Cristina Gama Vaz Rodrigues, Etevaldo Matos Maia Filho, Manoel Brito-Júnior, Rodrigo Dantas Pereira, Paula Prazeres Magalhães, Luiz de Macêdo Farias
BackgroundThe failure of endodontic treatment is linked to the presence of Enterococcus faecalis in the root canals. The scope of study was to evaluate the influence of the energy dose and frequency of photodynamic therapy (PDT cycles), as well as the volume of bacterial suspensions (BS) in the elimination of Enterococcus faecalis planktonic forms.MethodsIn four successive assays BS of Enterococcus faecalis ATCC 19433 were irradiated with a diode laser (40 mW) using the photosensitizer (PS) methylene blue (MB) (0.005 µg/mL). Group 1 - Effect of energy dose: 100 µ L of BS and 100 µ L of PS were irradiated by 1, 2.5, 5, 7.5 and 10 minute s. Group 2 - Effect of PDT cycles: The BS received 1, 2, 3 or 4 PDT cycles (in each cycle 100 m L of PS was added and irradiated by 2.5 minutes). Group 3 - Effect of energy dose and bacterial suspension volume: 10 µ L of BS and 10 µ L of PS were irradiated similar to group 1. Group 4 - Effect of energy dose, bacterial suspension volume and PDT cycles: 10 µ L of BS and 10 µL of PS were irradiated according to group 2. The laser source and MB isolated represented the controls.ResultsThe mean log reduction after separate applying laser light and MB were 0.01 and 0.07, respectively. It was found that wells with 100 µ L of BS irradiated with 2.4 to 24 J of energy did not cause significant bacterial elimination (p > 0.05), on the other hand PDT cycles above 12 J increased significantly bacterial elimination (p < 0.05). In 10 µ L wells irradiation from 12 J of energy provided higher bacterial elimination (p < 0.05) which combined with PDT cycle resulted in the logarithmic elimination of E. faecalis (p < 0.05).ConclusionsThe energy dose, the volume of the bacterial suspension and, especially, the PDT cycles optimized the bacterial elimination of Enterococcus faecalis planktonic forms.



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