Disinfection Effect of Microwave against Bacterial Biofilm on Acrylic Resin

Objectives: To evaluate the minimal time of microwave irradiation at 600 Watt, 850 Watt and 1,000 Watt to disinfect the bacterial biofilm on acrylic sample and to compare the disinfectant potential of microwave irradiation to that of heated water. Methods: The studied bacterias, S. mutans and S. aureus, were inoculated and established the biofilm on the acrylic resin specimens for 24 hours. The contaminated specimens were immersed in the tap water and disinfected by microwave oven for difference duration and power. Then the disinfected specimens were shaked in the Nacl solution to removed the survival microorganism. The Nacl suspension was serial diluted and cultured in the selective agar for plate count after 48 hours. Another group of contaminated specimens were disinfected by similar temperature water related to microwave oven. The Scanning Electron Microscope (SEM) was used to evaluated the morphology of the microorganism after been microwave disinfection. The data were analyzed by Two-way ANOVA. Results:  There was no viable cell being detected for both S. mutans and S. aureus after irradiated in microwave with powers 600 Watt for 120 seconds and 850 and 1,000 Watt for 90 seconds. There were no any difference between microwave group and high temperature water group. Conclusions:  The minimal time for microwave disinfection power 600 Watt is 120 senconds and for 850 Watt and 1000 Watt is 90 seconds and the main factors that affect the microwave disnifection is the temperature of water.