Control of DUWS Microbial Contamination in UK General Dental Practices

Water delivered by dental unit water systems (DUWS) in general dental practices may harbour high numbers of bacteria, including opportunistic pathogens. Biofilms in the tubing of DUWS provide a reservoir for these microbes, and so also need controlling. Objectives: This study evaluated three products in a head-to-head trial to control the bacterial load in UK DUWS outflow water to below the American Dental Association's guideline of 200 CFU/ml; this was part of a larger EU study. Methods: DUWS (n=13) in South West England were tested with Alpron, Bioblue and Sanosil. A four week baseline measurement of the microbial load of DUWS out-flowing water was followed by eight weeks of disinfection. Weekly water samples were tested for total viable counts (TVC) and, where possible, the effect of the products on biofilm TVC was also measured. Results: Baseline mean TVC before disinfection was 3.49 log CFU/ml). The products reduced the median TVC by 2.40 (Alpron), 3.39 (Bioblue) and 2.74 (Sanosil) log CFU/ml. During the treatment period, 81%, 92% and 87% of water samples were below the ADA guidelines of 200 CFU/ml when treated with Alpron, Bioblue and Sanosil, respectively. Biofilm TVCs were reduced to non-detectable levels following treatment with all three products. Conclusion: High bacterial numbers in untreated DUWS outflow water in GDPs are common, but treatment with particular disinfectant products can reduce the biofilm, and the microbial load of out-flowing water to <200 CFU/ml. This work was supported by the EC (QLK4 –00097-2000).