Studies of the effects photodynamic therapy antimicrobial and gene expression of S. Mutans biofilms and caries dentin

The application of Antimicrobial Photodynamic Therapy (PACT) in dentistry emerged as an effective treatment in reducing microbial populations present in oral biofilms and dental caries lesions. In this context, the objectives of this work are: a) to compare the antimicrobial effect of photodynamic therapy using different photosensitizers and evaluate the production of singlet oxygen for each of them (chapter 1), b) to determine the penetration degree of toluidine blue ortho dye (TBO) in in vitro and in situ demineralized dentin using confocal Raman microspectroscopy (chapter 2), c) to evaluate the antimicrobial effect of photodynamic therapy and its ability to alter the expression of genes gtfB, gtfC, gbpB and luxS in Streptococcus mutans oral biofilms formed in vitro (Chapter 3), d) to investigate the performance of PACT by the association of toluidine blue ortho and a light emitting diode using a clinical trial (chapter 4). As methodological approaches, in vitro, in situ and clinical studies were performed. The results showed that the TBO was the only photosensitizer, which significantly reduced the counts of S. mutans (p < 0.05). However, the singlet oxygen generation was not directly related to the bactericidal activity of PACT (Chapter 1). The TBO penetration profiles in sound and demineralized dentin in vitro and in situ were similar, besides different degrees of demineralization (chapter 2). While PACT has been effective in killing S. mutans biofilms formed in vitro, the change in virulence genes was observed only for luxS, a oxidative stress related gene (chapter 3). Finally, the results of clinical trial demonstrated that dentin caries lesions showed a decrease in the cariogenic microflora when treated with PACT (Chapter 4). In summary, antimicrobial photodynamic therapy is effective to kill S. mutans both as planktonic culture as well as biofilm, the photosensitizer used is able to penetrate into demineralized dentin in vitro and in situ, PACT can alter the expression of biofilm formation associated genes, and significantly reduce the in vivo microflora. However safe clinical protocols should be established for clinical use may be indicated.A aplicação da Terapia Fotodinâmica Antimicrobiana - TFA na Odontologia surge como um tratamento eficaz na redução das populações microbianas presentes nos biofilmes orais e nas lesões de cárie dental. Nesse contexto, os objetivos desse trabalho são: a)comparar o potencial antimicrobiano da TFA utilizando diferentes fotossensibilizadores e determinar a capacidade de produção de oxigênio singlete para cada um deles (capítulo 1); b) determinar o grau de penetração do corante azul de orto toluidina em dentina desmineralizada in vitro e in situ utilizando a microscopia confocal Raman (capítulo 2); c) avaliar o potencial antimicrobiano da TFA e sua habilidade de alterar a expressão dos genes gtfB, gtfC, gbpB e luxSem biofilmes orais de Streptococcus mutans formados in vitro (capítulo 3); d) investigar, através de um ensaio clínico, a performance da TFA utilizando a associação do azul de orto toluidina e um diodo emissor de luz (capítulo 4). Como abordagens metodológicas foram realizados estudos in vitro, in situ e um ensaio clínico. Como resultados, observou-se que o azul de orto toluidina foi o único fotossensibilizador que reduziu significantemente as contagens de S. mutans (p