Biofilm problems in dental unit water systems and its practical control

Journal of Applied Microbiology ISSN 1364-5072

REVIEW ARTICLE

Biofilm problems in dental unit water systems and its practical control
D.C. Coleman1, M.J. O’Donnell1, A.C. Shore1 and R.J. Russell2
1 Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, University of Dublin, Trinity College Dublin, Lincoln Place, Dublin 2, Ireland 2 Department ofMicrobiology, The Moyne Institute of Preventive Medicine, University of Dublin, Trinity College Dublin, Dublin 2, Ireland

Keywords biofilm, dental unit waterlines, disinfection. Correspondence David C. Coleman, Microbiology Research Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, University of Dublin, Trinity College Dublin, Lincoln Place, Dublin 2, Ireland. E-mail:david.coleman@dental.tcd.ie

Summary Dental chair units (DCUs) contain integrated systems that provide the instruments and services for a wide range of dental procedures. DCUs use water to cool and irrigate DCU-supplied instruments and tooth surfaces during dental treatment. Water is supplied to these instruments by a network of interconnected narrow-bore (2–3 mm) plastic tubes called dental unit waterlines(DUWLs). Many studies over the last 40 years demonstrated that DUWL output water is often contaminated with high densities of micro-organisms, predominantly Gram-negative aerobic heterotropic environmental bacteria, including Legionella and Pseudomonas species. Untreated DUWLs host biofilms that permit micro-organisms to multiply and disperse through the water network and which are aerosolized by DCUinstrument use, thus exposing patients and staff to these micro-organisms, to fragments of biofilm and bacterial endotoxins. This review concentrates on how practical developments and innovations in specific areas can contribute to effective DUWL biofilm control. These include the use of effective DUWL treatment agents, improvements to DCU supply water quality, DCU design changes, development ofautomated DUWL treatment procedures that are effective at controlling biofilm in the long-term and require minimal human intervention, are safe for patients and staff, and which do not cause deterioration of DCU components following prolonged use.

2008 ⁄ 1462: received 26 August 2008, revised 25 September 2008 and accepted 01 October 2008
doi:10.1111/j.1365-2672.2008.04100.x

Introduction Formore than a century, the dental chair unit (DCU) has been the single most essential item of equipment necessary for the practice of dentistry. Its original function was simply to provide support for patients while enabling easy access to the oral cavity by dental clinicians undertaking dental procedures. Over the decades DCUs have evolved considerably, combining all operating essentials into asingle, compact assembly. Modern DCUs consist of a variety of complex, integrated equipment systems that provide the services (e.g. air supply, water and electrical power) and instruments necessary for a diverse range of dental procedures (O’Donnell et al. 2005, 2006a; Coleman et al. 2007). DCUs use water to cool a range of
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DCU-associated instruments (e.g. conventional dental handpieces,high-speed turbine dental handpieces, threeway air ⁄ water syringes and ultrasonic scalers) and also to irrigate tooth surfaces during dental procedures, as the heat generated during instrument operation can be injurious to teeth (Stanley 1971; Langeland 1972; Siegel and von Fraunhofer 2002). DCU-supplied water is also used for oral rinsing by patients (water supplied via the cup filler outlet) and towash out the DCU spittoon, or cuspidor, after oral rinsing (water supplied via the bowlrinse outlet). An intricate network of interconnected narrow-bore tubes called dental unit waterlines (DUWLs) supplies water to all of the DCU-supplied instruments, cup-filler and bowl-rinse outlets (O’Donnell et al. 2006a; Coleman et al. 2007).

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