Evaluation of Bacterial Contamination of Water Supply in Dental Unit Water Lines at Zahedan Dental School 2008

: Background : Assessment of microbial contamination in dental unit waterlines has been focused on because of high risk of dangerous infections in immunocompromised patients. The purpose of this study was to evaluate the bacterial contamination of water supply in dental unit water lines at Zahedan Dental School. Materials and m ethods: In this descriptive analytical study we investigated 400 water samples collected from four parts of each unit including air/water syringe, turbine handpiece (before & after flushing), cup filler and 1 water sample collected from city water reservoir in Zahedan faculty of dentistry during 2008. Water samples were taken on Saturdays (the first working day in a week) and Wednesdays (the last working day in a week), before and after treatment on the same unit. Samples were transported in closed sterile containers to microbiology laboratory. All samples were incubated on blood agar and McCankey plates for 72 hours at 37 ° C . Bacterial contamination were then evaluted. Data were analyzed by ANOVA and t-test. Results: Total mean bacterial count was 6914 cfu/ml. Mean bacterial contamination on Saturdays (8859 cfu/ml) were higher than Wednesdays (4969 cfu/ml). Mean bacterial contamination before treatment was (5155 cfu/ml) less than the end of treatment (8673 cfu/ml) on the same unit. m ean bacterial contaminations of prosthetics clinic (13439cfu/ml) was higher than other clinics. The mean of periodentology clinic bacterial contaminations (3012 cfu/ml) was the least. Conclusion : The result of this study demonstrated that microbiological level of dental unit water lines is high. The dentists must be aware of the high level of microorganisms in the dental unit's water and thus minimize the risk of infection in both staff and patients.