Clinical disinfection of complete dentures by microwave irradiation

Objectives: This study evaluated in vivo the effectiveness of two exposure times of microwave irradiation on the disinfection of complete dentures. Methods: Thirty denture wearers were selected and divided into two treatment groups (n=15 each): 1- patients had their maxillary denture microwaved for 3min at 650W; 2- patients had their maxillary denture microwaved for 2min at 650W. Denture samples were taken with sterile cotton swab, before (left side surfaces) and after (right side surfaces) microwave irradiation. Microbial material was diluted (10⁰ to 10^-3) and plated on selective media for Candida spp. (CHROMagar), Staphylococcus spp. (Manitol Salt Agar), mutans Streptococci (SB20) and a non-selective media (Mueller Hinton). After incubation (48h/37ºC), the number of colony-forming units (cfu/ml) was counted. Microorganisms detected on the plates after microwave irradiation were identified using biochemical methods. The data were statistically analyzed by Kruskal-Wallis test (p<0.05). Results: No growth of microorganisms was observed after 3min of microwave irradiation. After 2min of irradiation, a significant decrease of Candida spp. (p=0.0062), Staphylococcus spp. (p=0.0178), mutans Streptococci (p=0.0047) and non-identified species (p<0.0001) was achieved compared to cfu/ml obtained before irradiation. The colonies grown after irradiation were identified as Candida albicans, non-aureus Staphylococci and Streptococcus mutans. Conclusion: Microwave irradiation promoted clinical sterilization at 3min and disinfection at 2min of complete dentures.

Grant: FAPESP 2005/02384-4 and 2005/02192-8