Evaluation of the level of microbial contamination and prevalence of gram-negative non-fermentative rods in dental unit waterlines

• Published in: Revista Sul-Brasileira de odontologia Vol. 9; no. 3; pp. 245 - 53
• Main Authors: Cinthia Regiane Kotaka, Lourdes Botelho Garcia, Fernanda Akemi Nakanishi Ito, Marcel Rodrigo Fuganti, João Carnio, Jacinta Sanchez Pelayo
• Format: Journal Article
• Language: English
• Published: 30.09.2013
• ISSN: 1984-5685; 1984-5685
• DOI: 10.21726/rsbo.v9i3.996

The cross infection control in dental office has received great attention from professionals and one of the critical points is the bacteriological control of water used in dental unit. Objective: To perform a microbiological evaluation of the water used in dental units, the identification of Gram-negative non-fermentative rods (GNNR) and their ability to adhere to polystyrene, and the antimicrobial activity of disinfectants on the identified strains. Material and methods: The heterotrophic bacteria count and GNNR identification were performed on water samples collected from 25 dental units (air/water syringe and reservoir). The GNNR were assessed on their capability to adhere to polystyrene and on their antimicrobial activity to the following disinfectants: sodium hypochlorite (0.06%, 0.12%, 0.25%, and 0.5%) and chlorhexidine (0.03%, 0.06%, and 0.12%). Results: 88% of the air/water syringe collected samples and 68% of the reservoir collected samples were out of the potability standards. The quantity of isolated bacteria from the reservoir was lower than from the air/water syringe in 88% of the dental units. Methylobacterium spp. was found in highest percentage (19.7%) during GNNR genus isolation. There was a weak adherence to polystyrene in 85.04% of the samples. Sodium hypochlorite at 0.25%, inactivated 100% of the GNNRs in 10 minutes, while the highest tested concentration of chlorhexidine (0.12%), inactivated 98.5% of the GNNRs. Conclusion: These results provide information on the contamination problem of dental unit waterlines (DUWL) and indicate a need for treatment of the water used in dental units. The disinfection of DUWL can be performed with sodium hypochlorite at 0.25% (half the concentration recommended in the literature). However, further studies are necessary regarding DUWL frequency disinfection.