title: Microwave disinfection of complete dentures contaminated in vitro with selected bacteria.
abstract: OBJECTIVE
  This study evaluated the effectiveness of microwave irradiation for disinfection of simulated complete dentures.
  
  
  METHODS
  Seventy dentures were fabricated in a standardized procedure, subjected to ethylene oxide sterilization, individually inoculated (10(7) cfu/mL) with Staphylococcus aureus (n = 20), Pseudomona aeruginosa (n = 20), and Bacillus subtilis (n = 30) and incubated for 24 hours at 37 degrees C. After that, 40 dentures were selected for microwaving. For each microorganism, 10 dentures were submitted to microwave irradiation at 650 W for 3 minutes. In addition, 10 dentures contaminated with B. subtilis were irradiated for 5 minutes. Thirty non-microwaved dentures (n = 10 for each bacteria) were used as positive controls. Replicate aliquots (25 microL) of suspensions were plated at dilutions of 10(-3) to 10(-6) on plates of selective media appropriate for each organism. After incubation (37 degrees C for 48 hours), colonies were counted (cfu/mL). TSB beakers with the microwaved dentures were incubated at 37 degrees C for a further 7 days to verify long-term disinfection. The data were statistically analyzed by the Kruskal-Wallis test (alpha= 0.05).
  
  
  RESULTS
  No evidence of growth was observed at 48 hours for S. aureus and P. aeruginosa on plates, and no turbidity was visible in the TSB beakers of these specimens after 7 days of incubation. Dentures contaminated with B. subtilis and irradiated for 3 minutes produced microbial growth on six plates and turbidity on all TSB beakers. Microwaving for 5 minutes resulted in survival of B. subtilis in two plates and two beakers.
  
  
  CONCLUSIONS
  Microwave irradiation for 3 minutes at 650 W produced sterilization of complete dentures contaminated with S. aureus and P. aeruginosa. Dentures contaminated with B. subtilis were disinfected by microwave irradiation after 3 and 5 minutes at 650 W.
authors.affiliation: Department of Dental Materials and Prosthodontics, São Paulo State University, UNESP, Araraquara Dental School, São Paulo, Brazil.
authors.forename: Lívia Nordi
authors.initials: LN
authors.lastname: Dovigo
authors.forename: Ana Cláudia
authors.initials: AC
authors.lastname: Pavarina
authors.forename: Daniela Garcia
authors.initials: DG
authors.lastname: Ribeiro
authors.forename: Juliana Aparecida
authors.initials: JA
authors.lastname: de Oliveira
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Vergani
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Machado
mesh_terms: D001412:Bacillus subtilis / Q000528:radiation effects; D015169:Colony Count, Microbial; D003764:Dental Materials / Q000528:radiation effects; D003827:Denture, Complete, Upper / Q000382:microbiology*; D004203:Disinfection / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008872:Microwaves / Q000627:therapeutic use*; D011550:Pseudomonas aeruginosa / Q000528:radiation effects; D013211:Staphylococcus aureus / Q000528:radiation effects; D013242:Sterilization / Q000295:instrumentation / Q000379:methods; D013997:Time Factors
chemical_list: D003764:Dental Materials