Effectiveness of Six Different Disinfectants on Removing Five Microbial Species and Effects on the Topographic Characteristics of Acrylic Resin Francine Cristina da Silva, MSc, 1 Estev ˜ ao Tomomitsu Kimpara, DDS, PhD, 2 Maria Nadir Gasparotto Mancini, PhD, 1 Ivan Balducci, MSc, 3 Antonio Olavo Cardoso Jorge, PhD, 1 & Cristiane Yumi Koga-Ito, PhD 1 1 Department of Oral Biosciences and Diagnosis, S ˜ ao Jos ´ e dos Campos Dental School, S ˜ ao Paulo State University (UNESP), S ˜ ao Paulo, Brazil 2 Department of Oral Prosthesis and Dental Materials, S ˜ ao Jos ´ e dos Campos Dental School, S ˜ ao Paulo State University (UNESP), S ˜ ao Paulo, Brazil 3 Department of Dental Clinics and Social Dentistry, S ˜ ao Jos ´ e dos Campos Dental School, S ˜ ao Paulo State University (UNESP), S ˜ ao Paulo, Brazil Keywords Acrylic resins; disinfection; dental prothesis; disinfectants; infection control; surface properties; surface roughness. Correspondence Cristiane Yumi Koga-Ito, Department of Oral Biosciences and Diagnosis, School of Dentistry, UNESP, Av. Eng., Francisco Jos ´ e Longo, Number 777, S ˜ ao Jos ´ e dos Campos, S˜ ao Paulo, Brazil, C.E.P. 12.245-000. E-Mail: cristianeykito@directnet.com.br This study was supported by FAPESP (Fundac ¸˜ ao de Amparo ` a Pesquisa do Estado de S ˜ ao Paulo—Process number 2005/57029-4). Accepted September 12, 2007 doi: 10.1111/j.1532-849X.2008.00358.x Abstract Purpose: The aim of this study was to evaluate the effectiveness of disinfectant solutions (1% sodium hypochlorite, 2% chlorhexidine digluconate, 2% glutaraldehyde, 100% vinegar, tabs of sodium perborate-based denture cleanser, and 3.8% sodium perborate) in the disinfection of acrylic resin specimens (n = 10/group) contaminated in vitro by Candida albicans, Streptococcus mutans, S. aureus, Escherichia coli, or Bacillus subtilis as measured by residual colony-forming unit (CFU). In a separate experiment, acrylic resin was treated with disinfectants to monitor potential effects on surface roughness, Ra (μm), which might facilitate microbial adherence. Materials and Methods: Three hundred fifty acrylic resin specimens contaminated in vitro with 1×10 6 cells/ml suspensions of standard strains of the cited microorganisms were immersed in the disinfectants for 10 minutes; the control group was not submitted to any disinfection process. Final counts of microorganisms per ml were performed by plating method for the evaluation of microbial level reduction. Results were compared statistically by ANOVA and Tukey’s test (p ≤ 0.05). In a parallel study aiming to evaluate the effect of the tested disinfectant on resin surface, 60 specimens were analyzed in a digital rugosimeter before and after ten cycles of 10-minute immersion in the disinfectants. Measurements of superficial roughness, Ra (μm), were compared statistically by paired t-test (p ≤ 0.05). Results: The results showed that 1% sodium hypochlorite, 2% glutaraldehyde, and 2% chlorhexidine digluconate were most effective against the analyzed microorganisms, followed by 100% vinegar, 3.8% sodium perborate, and tabs of sodium perborate-based denture cleanser. Superficial roughness of the specimens was higher after disinfection cycles with 3.8% sodium perborate (p = 0.03) and lower after the cycles with 2% chlorhexidine digluconate (p = 0.04). Conclusion: Within the limits of this experiment, it could be concluded that 1% sodium hypochlorite, 2% glutaraldehyde, 2% chlorexidine, 100% vinegar, and 3.8% sodium perborate are valid alternatives for the disinfection of acrylic resin. Prosthodontics has been cited as one of the dental specialties that most neglect cross-infection control measures during clini- cal and laboratory procedures. Cotrim et al 1 related that 52% of dentists interviewed did not believe in the possibility of cross- infection between the dental office and laboratory. There are several routes of microbial contamination in den- tal laboratories, including the felt disks and pumice used in the polishing process and contact with contaminated hands. Other forms of contamination occur when prostheses are sent to den- tal offices for adjustments or repairs, because in certain steps of treatment, these materials may be contaminated by microor- ganisms from the patient’s oral cavity. 1,2 Microbial adherence capacity is influenced by differences in the surfaces of prostheses. 3,4 Davenport 5 suggested that the roughness in prostheses’ surfaces may cause micro traumas in oral tissues, and Williams and Lewis 6 concluded that surface Journal of Prosthodontics 17 (2008) 627–633 c  2008 by The American College of Prosthodontists 627