Reduction of CFUs in high-speed handpiece water lines over time

Many methods are being investigated for reducing bacteria in the high-speed water lines of dental units. One of these is flushing water through the water lines prior to use. The objective of this study was to determine the actual change over time in the number of CFUs during flushing. Four consecutive samples were collected over time from the water lines of 20 different dental units that had been in disuse for over 48 hours. Next, autoclaved handpieces were connected and two additional samples were obtained. After culturing and determining CFUs per ml, data were analyzed to determine differences between samples. There were significant reductions between the first and second, second and third, third and fourth samples prior to adding the handpiece. There were no significant differences in the next two samples obtained after adding the handpiece.