title: Effect of photodynamic therapy with two photosensitizers on Streptococcus mutants: In vitro study.
abstract: OBJECTIVE
  Streptococcus mutans (S. mutans) colonizes the oral cavity and causes dental caries and periodontal diseases. Considering the importance of the treatments that decrease pathogenic microorganisms, the aim of the present research was the assessment of the antimicrobial effect of Photodynamic Therapy (PDT) with Methylene Blue (MB) and Indocyanine Green (IG) photosensitizers on S. mutans.
  
  
  METHODS
  In this In vitro experimental study, Sixty four caries-free first premolars were contaminated with 0.5 McFarland S.mutans suspension and were randomly assigned to 4 groups. The teeth in the first group were impregnated with 2% MB while the teeth in the second group were impregnated with 0.2% IG. The teeth in the first group were irradiated with continuous-wave 660nm dod laser with 40mw output power, energy density of 2.4J/cm2and 100% duty cycle for 60s, while the teeth in the second group were irradiated with continuous -wave 810nm diode laser with 100mw out power, density energy of 6J/cm2and 100% duty cycle for 60s in contact mode. In the third group, the teeth were suspended in 0.2% Chlorhexidine for 30s. The fourth group was considered as the control. The teeth were sampled before and after the interventions and the samples were incubated in Blood Agar for 24h. Afterwards, the number of S. mutans colonies were counted. Data were statistically analyzed by Kruskal-Wallis, Dunn's and Friedman tests.
  
  
  RESULTS
  In the groups treated with a combination of MB and IG and laser irradiation and also in the Chlorhexidine group, the final number of S. mutans colonies equaled zero. In "MB and IG groups without laser irradiation", although the amount of microorganisms decreased, but the number of colonies did not reach zero. Pair comparisons by Dunn's test showed that there was a significant difference between "MB and IG groups without laser irradiation" and the other experimental groups p=0.03).
  
  
  CONCLUSIONS
  PDT with MB and IG photosensitizers and also Chlorhexidine mouthwash, have the ability to completely eradicate S. mutans bacterial colonies.
authors: Islamic Azad University, Dental Branch, Tehran, Iran. Electronic address: drarashazizi@yahoo.com.
authors: Arash
authors: A
authors: Azizi
authors: Islamic Azad University, Dental Branch, Tehran, Iran. Electronic address: samira_dentist_2020@yahoo.com.
authors: Samira
authors: S
authors: Shademan
authors: Microbiology Department, Islamic Azad University, Dental Branch, Tehran, Iran. Electronic address: maryamrezai_51@yahoo.com.
authors: Maryam
authors: M
authors: Rezai
authors: Biophysics Department, Islamic Azad University, Science and Research Branch, Tehran, Iran. Electronic address: arash_dds@yahoo.com.
authors: Arash
authors: A
authors: Rahimi
authors: Islamic Azad University, Dental Branch, Tehran, Iran. Electronic address: drshlawaf@yahoo.com.
authors: Shirin
authors: S
authors: Lawaf
mesh_terms: D001641:Bicuspid / Q000187:drug effects* / Q000382:microbiology*; D002470:Cell Survival / Q000187:drug effects; D004203:Disinfection / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004359:Drug Therapy, Combination / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques; D007208:Indocyanine Green / Q000008:administration & dosage*; D008027:Light; D008751:Methylene Blue / Q000008:administration & dosage*; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D013295:Streptococcus mutans / Q000187:drug effects* / Q000502:physiology; D016896:Treatment Outcome
chemical_list: D017319:Photosensitizing Agents; D007208:Indocyanine Green; D008751:Methylene Blue
keywords: Indocyanine green; Laser; Methylene blue; Photodynamic therapy; Photosensitizing agents; Streptococcus mutans