Bacteriological Evaluation of Closed Dental Unit Supply Water Systems

Objectives: It was reported that water from dental lines can be heavily contaminated with micro-organisms. Dental unit water contamination is due to microcolonies of proliferating micro-organisms on the inner surface of the water lines, hand-pieces, and unit tubes. dental unit draws water from general water supply ( opened system ) or from reservoirs ( closed system ). To determine the microbiological quality of water from dental units in a general practice setting with closed system and to compare the quality of general supply water with this in the reservoir.

Methods: Twenty dental clinics were included in this study, in each clinic the water was sampled from the reservoir and from the supplying water with a sterile syringe, the samples were cultured on Blood Agar medium and incubated for 24 hours at 37 c° and the total bacterial count was done. Data were analyzed by the computer software SPSS version 17 by means of two tests, Wilcoxon and Spearman
Results: The Interquartile Range for the bacterial count in general water supply was 1800, with minimum count of 0, and maximum count of 4000. While Interquartile Range in the reservoir was 12200 with minimum count of 200, and maximum count of 20000.
Conclusions: The microbiological quality of water in the reservoir of dental units in general dental practice is poor compared with that from general water supply, sterile irrigants should be used for surgical procedures in dental practice. Further work is required for decontamination regimens of the reservoir of dental unit using closed water system