How Does Time‐Dependent Dental Unit Waterline Flushing Affect Planktonic Bacteria Levels?

Abstract

The purpose of this study was to evaluate how time-dependent waterline flushing affects the presence of biofilm in otherwise-untreated dental unit waterlines (DUWLs). Water samples were obtained from twelve highspeed handpiece DUWLs located in the undergraduate treatment clinic at the University of Missouri-Kansas City, School of Dentistry. Baseline water samples (50 cc) were collected prior to the start of continuous flushing. Additional 50 cc samples were collected after two-, three-, and four-minute flushing intervals from the baseline. The levels of planktonic bacteria in DUWLs were quantified by counting colony forming units (CFUs). In addition, segments of water tubing from each of the highspeed handpiece waterlines were examined by scanning electron microscopy, which confirmed the presence of a residual biofilm in the lumen of each dental unit waterline. A one-factor repeated measures ANOVA showed a statistically significant (p< 0.01) reduction in CFUs at all intervals compared to baseline and between each successive time interval. Indeed, after four minutes of continuous flushing, all waterlines still harbored CFU levels that exceed current American Dental Association (ADA) recommendations. It was concluded that water flushing of DUWLs produced a statistically significant reduction in planktonic bacteria at each time interval compared to the baseline and between each successive time interval. However, the level of CFUs after four minutes of continuous water flushing still exceeds the current ADA recommendations for acceptable levels of microorganisms.

An audit improves the quality of water within the dental unit water lines of general dental practices across the East of England

“…My thanks to all of the dentists who participated in this audit, to Martin each time interval, compared to baseline and between each time interval. 38 The slight reduction in the mean levels of DUWL contamination between the pre-start and midsession samples from the pre-audit survey stage of this study (Tables 3 and 4), as well as the halving of the mean readings taken between the pre-start and mid-session samples during the audit stage (Tables 6 and 7) would seem to bear this out.…”

Dental unit water: bacterial decontamination of old and new dental units by flushing water

“…The municipal water distribution systems may be connected directly to dental units (23, 25, 27, 35). Nevertheless, water may supply independent reservoirs made of metal, plastic or glass.…”

“…The flushing times have been reported from 1 to 20 min (9, 22–27, 35). All authors observed a reduction of bacterial contamination in dental unit water.…”

“…The Plate Count Agar medium has been used to count total aerobic bacteria in water by pour plate technique (3, 24). Moreover, the employment of plating onto surface of R 2 A Agar and Trypticase Soy Agar, as well as the use of membrane filtration technique is reported in the literature (24, 25, 27, 36, 39).…”

“…Several authors have been reported flushing water through waterlines to reduce the level of microbial contamination of dental unit water (22–27).…”