title: Photodynamic therapy with two different photosensitizers as a supplement to instrumentation/irrigation procedures in promoting intracanal reduction of Enterococcus faecalis.
abstract: BACKGROUND
  This in vitro study aimed to investigate the antibacterial effects of photodynamic therapy (PDT) with methylene blue (MB) or toluidine blue (TB) (both at 15 microg/mL) as a supplement to instrumentation/irrigation of root canals experimentally contaminated with Enterococcus faecalis.
  
  
  METHODS
  Seventy extracted teeth had their root canals contaminated with an endodontic strain of E. faecalis for 7 days, instrumented with nickel-titanium instruments and irrigated either with 2.5% NaOCl or with 0.85% NaCl, and then randomly distributed into four experimental groups: MB/NaOCl (PDT with MB and NaOCl as the irrigant), TB/NaOCl (PDT with TB and NaOCl as the irrigant), MB/NaCl (PDT with MB and NaCl as the irrigant), and TB/NaCl (PDT with TB and NaCl as the irrigant). For PDT, the photosensitizer remained in the canal for 2 minutes before exposed to red light emitted from a diode laser for 4 minutes. Samples were taken before and after instrumentation/irrigation and following the specific PDT procedure for each group, plated onto Mitis-salivarius agar and the colony forming units counted.
  
  
  RESULTS
  Regardless of the irrigant used (NaOCl or NaCl), instrumentation significantly reduced bacterial counts in comparison to the baseline (p < 0.001). NaOCl as the irrigant was significantly more effective than NaCl, and this difference persisted after PDT, irrespective of the photosensitizer used (p < 0.05). PDT with either MB or TB did not significantly enhance disinfection after chemomechanical preparation using NaOCl as irrigant (p > 0.05). No significant differences were observed between the two photosensitizers (p > 0.05).
  
  
  CONCLUSIONS
  These in vitro results suggest that PDT with either MB or TB may not exert a significant supplemental effect to instrumentation/irrigation procedures with regard to intracanal disinfection. Further adjustments in the PDT protocol may be required to enhance predictability in bacterial elimination before clinical use is recommended.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Brazil.
authors.forename: Letícia C
authors.initials: LC
authors.lastname: Souza
authors.forename: Patrícia R R
authors.initials: PR
authors.lastname: Brito
authors.forename: Julio C Machado
authors.initials: JC
authors.lastname: de Oliveira
authors.forename: Flávio R F
authors.initials: FR
authors.lastname: Alves
authors.forename: Edson J L
authors.initials: EJ
authors.lastname: Moreira
authors.forename: Hélio R
authors.initials: HR
authors.lastname: Sampaio-Filho
authors.forename: Isabela N
authors.initials: IN
authors.lastname: Rôças
authors.forename: José F
authors.initials: JF
authors.lastname: Siqueira
mesh_terms: D015169:Colony Count, Microbial; D003131:Combined Modality Therapy; D003786:Dental Pulp Cavity / Q000382:microbiology* / Q000528:radiation effects; D004203:Disinfection / Q000295:instrumentation / Q000379:methods; D013293:Enterococcus faecalis / Q000528:radiation effects*; D006801:Humans; D008751:Methylene Blue / Q000627:therapeutic use; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000379:methods*; D012965:Sodium Chloride / Q000627:therapeutic use; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D018709:Statistics, Nonparametric; D014048:Tolonium Chloride / Q000627:therapeutic use
chemical_list: D017319:Photosensitizing Agents; D012388:Root Canal Irrigants; D014048:Tolonium Chloride; D012965:Sodium Chloride; D012973:Sodium Hypochlorite; D008751:Methylene Blue