Background and aims. Current chemical methods may not efficiently disinfect dental stone casts. The aim of this study
was to investigate if microwave irradiation is effective for disinfection of stone casts.
Materials and methods. In this laboratory study, three groups (n = 162) of prepared spherical stone beads as carriers
with a diameter of 10 mm were inoculated by separately soaking in three broth culture media, each containing a study microorganism—Pseudomonas
aeruginosa, Staphylococcus aureus or Candida albicans. Six inoculated carriers were used for
every test, including irradiation in a household microwave oven at 300, 450, 600 or 900 W energy level, or soaking in
0.03%, 0.06%, 0.12%, 0.25% or 0.50% concentration of sodium hypochlorite solution, at 1, 2, or 3-minute test times. Positive
and negative control groups were considered for each test. All treated carriers were then individually transferred to nutrient
broth culture medium and one milliliter from each tube was cultured in nutrient agar media over night. Colony forming
unit per milliliter (CFU/mL) was counted, and multi-factor ANOVA was used to analyze data (α = 0.05).
Results. Microwave irradiation at 600 W resulted in high-level disinfection in 3 minutes. Immersion of the stone casts in
hypochlorite solution at 0.06% concentration resulted in disinfection after 2 minutes.
Conclusion. According to the results, high level disinfection of the stone casts can be achieved by microwave irradiation
at 600 W in 3 minutes, similar to a validated chemical method