title: Evaluation of antibacterial photodynamic therapy effects on human dental pulp cell cultures.
abstract: BACKGROUND
  The antibacterial photodynamic therapy (aPDT) has been used in dentistry against oral microorganisms because of its excellent biocide effect. However, for carious lesions applications, there is little evidence that this therapy is safe for the pulp tissue.
  
  
  OBJECTIVE
  This study evaluates the effects of an aPDT protocol on human pulp cells in vitro.
  
  
  METHODS
  Pulp cells isolated from dental pulp were exposed to an aPDT protocol associating methylene blue (MB) at concentrations of 0.0125, 0.025 and 0.050mg/ml and red laser irradiation using a continuous-wave indium-gallium-aluminum-phosphide (InGaAlP) diode laser (λ=660nm, 40mW, 2.4J, 60J/cm(2) for 1min). Pre-irradiation time was 5min for each MB concentration. Cell viability was determined by MTT assay and activity of alkaline phosphatase was assessed by BCIP-NBT assay. Type of aPDT-induced cell death was assessed by flow cytometry. Data was statistically compared (ANOVA followed by Tukey' or Bonferroni's post hoc tests).
  
  
  RESULTS
  aPDT was able to kill pulp cells in a dye concentration-dependent manner. The cellular viability was significantly reduced when used MB at 0.025 or 0.050mg/ml concentrations (p<0.0001). At these concentrations, aPDT-induced cell death occurred mostly by necrosis. Alkaline phosphatase activity was significantly reduced in all experimental groups (p<0.001). Pulp cells showed suitable viability when MB at 0.0125mg/ml was exposed to laser irradiation.
  
  
  CONCLUSIONS
  aPDT with MB at 0.0125mg/ml may represent a low-risk therapy for restorative dentistry applications. aPDT protocol using concentrations above 0.025mg/ml of MB associating red laser irradiation may be harmful for dental pulp cells.
authors.affiliation: Restorative Dentistry Departament, Universidade Federal de Minas Gerais (UFMG), Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, Brazil.
authors.forename: Ivana Márcia Alves
authors.initials: IM
authors.lastname: Diniz
authors.affiliation: Restorative Dentistry Departament, Universidade Federal de Minas Gerais (UFMG), Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, Brazil.
authors.forename: Karina Imaculada Rosa
authors.initials: KI
authors.lastname: Teixeira
authors.affiliation: Restorative Dentistry Departament, Universidade Federal de Minas Gerais (UFMG), Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, Brazil.
authors.forename: Patrícia Valente
authors.initials: PV
authors.lastname: Araújo
authors.affiliation: Centro de Pesquisas René Rachou, Fundação Osvaldo Cruz, Avenida Augusto de Lima 1715, CEP 30190-002 Belo Horizonte, Brazil.
authors.forename: Márcio Sobreira Silva
authors.initials: MS
authors.lastname: Araújo
authors.affiliation: Restorative Dentistry Departament, Dentistry Faculty, Universidade de São Paulo, Prof. Lineu Prestes, 2227, CEP 05508-000 São Paulo, Brazil.
authors.forename: Márcia Martins
authors.initials: MM
authors.lastname: Marques
authors.affiliation: Restorative Dentistry Departament, Universidade Federal de Minas Gerais (UFMG), Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, Brazil.
authors.forename: Luiz Thadeu de Abreu
authors.initials: LT
authors.lastname: Poletto
authors.affiliation: Restorative Dentistry Departament, Universidade Federal de Minas Gerais (UFMG), Avenida Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, Brazil. Electronic address: mecortes@ufmg.br.
authors.forename: Maria Esperanza
authors.initials: ME
authors.lastname: Cortés
mesh_terms: D000293:Adolescent; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008751:Methylene Blue / Q000008:administration & dosage*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D017319:Photosensitizing Agents; D008751:Methylene Blue
keywords: Antibacterial photodynamic therapy; Cytotoxicity; Dental pulp cell; Methylene blue; Red laser