Comparison of effectiveness of microwave disinfection on wet and dry type III dental stone casts contaminated with bacterial and fungal strains

Abstract

Objectives: Dental practice contains the use of instruments and multiuse items that should be sterilized or disinfected properly. The aim of the current study was to investigate the effect of microwave irradiation on dental stone cast disinfection in moist and dry condition. Materials and Methods : In this in vitro study, 76 stone casts were prepared by a sterile method. The casts were contaminated by Pseudomonas aeruginosa (ATCC 9027), Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212) as well as Candida albicans (ATCC 10231). Half the samples were dried for two hours and the other half was studied while still moist. The samples were irradiated by a household microwave at 600 W for 3, 5 and 7 minutes. The microorganisms on the samples were extracted by immersion in tryptic soy broth and .001 ml of that were cultured in nutrient agar media,incubated over night and counted and recorded as colony forming unit per milliliter (CFU/mL) . Results: The findings showed that microorganisms were reduced to 4.87 logarithem of CFU/mL value on dental cast within seven minutes in comparison with positive control. Although microbial count reduction was observed as a result of exposure time increase, comparison between moist and dried samples showed no significant difference. Conclusions: Seven-minute microwave irradiation at 600 W can effecte in considerable reducing the microbial load of dental stone casts. Wetting of the casts does not seem to alter the efficacy of irradiation.