Purpose: The aim of this study was to evaluate the effectiveness of microwave irradiation
sterilization on hard chairside reline resins. Materials and Methods: Specimens of three
reline resins (Kooliner, Tokuso Rebase, and Ufi Gel Hard) were fabricated and subjected to
ethylene oxide sterilization. The specimens were then individually inoculated (107 cfu/mL)
with Tryptic Soy Broth media containing one of the tested microorganisms (C albicans, S
aureus, B subtilis,and P aeruginosa).After 48 hours at 37°C, the samples were vortexed for
1 minute and allowed to stand for 9 minutes, followed by a short vortex to resuspend any
organisms present. After inoculation, 40 specimens of each material were immersed in 200
mL of water and subjected to microwave irradiation at 650 W for 6 minutes. Forty nonirradiated
specimens were used as positive controls. Replicate specimens (25 µL) of suspension
were plated at dilutions of 10–3 to 10–6 on plates of selective media appropriate for
each organism. All plates were incubated at 37°C for 48 hours. After incubation, colonies
were counted, and the data were statistically analyzed by the Kruskal-Wallis test. Twelve
specimens of each material were prepared for SEM. Results: All immersed specimens
showed consistent sterilization of all the individual organisms after microwave irradiation.
SEM examination indicated an alteration in cell morphology after microwave irradiation.
Conclusion: Microwave sterilization for 6 minutes at 650 W proved to be effective for the
sterilization of hard chairside reline resins. Int J Prosthodont 2003;16:616–620.