Background: The aim of the present study was the evaluation of the effectiveness as sterilizer of a modified version of a microwave device, which was previously tested by the same authors and found unsatisfactory.
Materials and methods: Dental mirrors were contaminated by 10(4)-10(9) microorganisms of Stapbylococcus aureus and spores of Bacillus subtilis and Bacillus stearothermophilus. The inocula used were both wet and dry. The duration of the treatment was 4 minutes. Three series of tests were made: 1) microwaves and "adjuvant" solution (as suggested by the producer of the device); 2) microwaves only (in place of the "adjuvant" solution, a Na Cl 0.9% was used); 3) "adjuvant" solution only (into an oven at 25 degrees C).
Results: In the 1st and 3rd series of tests all the microorganisms and the spores were killed. In the 2nd series of tests a bactericidal effect against some, not all, microorganisms of the S. aureus species and against spores of B. subtilis and B. stearothermophilus was found.
Conclusions: The results of this study suggest that the device tested has a sterilizing activity, which, however, is not due to the activity of microwaves only; but to the combined activity of microwaves, "adjuvant" solution and temperature (since inside the device, at the end of the treatment the temperature on the mirrors was 94 degrees C).