Microwave Disinfection of Complete Dentures Contaminated In Vitro with Selected Bacteria L´ ıvia Nordi Dovigo, DDS, MSc, 1 Ana Cl ´ audia Pavarina, DDS, MSc, PhD, 2 Daniela Garcia Ribeiro, DDS, MSc, 1 Juliana Aparecida de Oliveira, DDS, 3 Carlos Eduardo Vergani, DDS, MSc, PhD, 2 & Ana Lucia Machado, DDS, MSc, PhD 2 1 Postgraduate student, Department of Dental Materials and Prosthodontics, S ˜ ao Paulo State University, UNESP, Araraquara Dental School, S˜ ao Paulo, Brazil 2 Associate Professor, Department of Dental Materials and Prosthodontics, S ˜ ao Paulo State University, UNESP, Araraquara Dental School, S˜ ao Paulo, Brazil 3 Dentist, Graduated from S ˜ ao Paulo State University, UNESP, Araraquara Dental School, S ˜ ao Paulo, Brazil Keywords Disinfection; microwaves; complete denture; infection control. Correspondence Dr. Ana Cl ´ audia Pavarina, Faculdade de Odontologia de Araraquara – UNESP, Rua Humait ´ an ◦ 1680, Araraquara, S ˜ ao Paulo, Brazil, CEP 14801-903. E-mail: pavarina@foar.unesp.br This research was supported by S ˜ ao Paulo Council of Research (FAPESP Grant No. 2005/02384-4). Accepted August 29, 2008 doi: 10.1111/j.1532-849X.2009.00489.x Abstract Purpose: This study evaluated the effectiveness of microwave irradiation for disinfec- tion of simulated complete dentures. Materials and Methods: Seventy dentures were fabricated in a standardized proce- dure, 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 ◦ 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 μL) of suspensions were plated at dilutions of 10 −3 to 10 −6 on plates of selective media appropriate for each organism. After incubation (37 ◦ C for 48 hours), colonies were counted (cfu/mL). TSB beakers with the microwaved dentures were incubated at 37 ◦ C for a further 7 days to verify long-term disinfection. The data were statistically analyzed by the Kruskal-Wallis test (α = 0.05). Results: No evidence of growth was observed at 48 hours for S. aureus and P. aerug- inosa 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. Conclusion: Microwave irradiation for 3 minutes at 650 W produced sterilization of complete dentures contaminated with S. aureus and P. aeruginosa. Dentures contami- nated with B. subtilis were disinfected by microwave irradiation after 3 and 5 minutes at 650 W. Prostheses contaminated with pathogenic microorganisms serve as a potential source of infection transmission between patients and dental personnel. 1 Concern about dissemination of these organisms has produced renewed interest in denture ster- ilization and disinfection. 2,3 To prevent cross-contamination, prostheses should be completely disinfected before being sent to the laboratory and before insertion. Several methods of disinfection have been recommended to ensure infection control in dental practice. Proper disinfection of prostheses can be achieved with chemical solutions such as sodium hypochlorite, glutaraldehyde, and chlorine diox- ide. 4,5 Nevertheless, these denture-soaking solutions can cause deleterious effects on acrylic resins. Sodium hypochlorite may stain 6 or whiten the plastic components of prostheses. 4 Glu- taraldehyde has shown severe risk of cytotoxicity. 7 Chlorine dioxide has a bleaching action on the denture base resin and corrosive effects on the frameworks. 8 To overcome the problems associated with chemical solu- tions, a major research effort has been focused on alternative methods for prosthesis decontamination. Microwave irradiation is claimed to be a simple, effective, and inexpensive method for prosthesis disinfection. 9-12 Webb et al 9 indicated that mi- crowaving may be a more effective method of denture steriliza- tion than denture soaking in sodium hypochlorite. A study by Journal of Prosthodontics 18 (2009) 611–617 c  2009 by The American College of Prosthodontists 611