By Leslie Canham, CDA, RDAProper infection control interrupts the spread of disease agents. To be confident that our offices are safe places to deliver dental care, we must be vigilant in our infection control practices. One area of infection control that is often overlooked is making sure dental unit water is safe. Although no epidemiologic evidence indicates a public health problem, the presence of substantial numbers of pathogens in dental unit waterlines generates concern. Exposing patients or dental health-care workers to water of uncertain microbiological quality, despite the lack of documented adverse health effects, is not consistent with accepted infection control principles.1Standards for safe drinking water quality are established by the Environmental Protection Agency (EPA), the American Public Health Association (APHA), and the American Water Works Association (AWWA). These authorities dictate that safe drinking water may not exceed 500 Colony Forming Units per milliliter (CFU/mL) of heterotrophic bacteria. Dental unit water should be as safe as drinking water. How do I test dental unit waterlines for bacteria?The Centers for Disease Control (CDC) recommends monitoring dental unit water quality to ensure that bacterial counts are below 500 CFU/mL. Monitoring can be performed with commercial self-contained test kits or commercial water-testing laboratories. Some dental schools, such as Loma Linda University, offer dental unit waterline testing. What are strategies to improve dental unit water quality?In 1993, the CDC recommended that dental unit waterlines be flushed at the beginning of each clinic day to reduce the microbial load. However, studies have demonstrated this practice does not affect biofilm* in the waterlines or reliably improve the quality of water used during dental treatment. The recommended value of <500 CFU/mL cannot be achieved using this method, so other strategies should be employed. Dental unit water that remains untreated or unfiltered is unlikely to meet drinking water standards.1To control water quality, the CDC lists the following recommendations:1. Use water that meets EPA regulatory standards for drinking water (i.e., <500 CFU/mL of heterotrophic water bacteria) for routine dental treatment output water.2. Consult with the dental unit manufacturer for appropriate methods and equipment to maintain the recommended quality of dental water.3. Follow recommendations for monitoring water quality provided by the manufacturer of the unit or waterline treatment product.4. Discharge water and air for a minimum of 20 to 30 seconds after each patient, from any device connected to the dental water system that enters the patient’s mouth (e.g., handpieces, ultrasonic scalers, and air/water syringes).5. Consult with the dental unit manufacturer on the need for periodic maintenance of anti retraction mechanisms.What else can be done to improve water quality?Commercial devices designed to improve the quality of water used in dental treatment include self-contained water systems combined with chemical treatment, in-line microfilters, and water conditioning systems. Water conditioning systems that treat water by filtration, sedimentation, and/or ultraviolet germicidal irradiation (UVGI) can improve water quality, but have no residual affect on planktonic (free-floating) bacteria or biofilm within the dental unit.2Simply using source water containing <500 CFU/mL of bacteria (e.g., tap, distilled, or sterile) in a self-contained water system will not eliminate bacterial contamination in treatment water if biofilms in the water system are not controlled. Removal or inactivation of dental waterline biofilms requires use of chemical germicides.1 Before using any chemical germicide, check with the manufacturer of the dental unit for compatibility. Special precautions when performing oral surgical proceduresDo not use dental unit water when performing oral surgical procedures. Instead, sterile solutions, either sterile saline or sterile water, should be used as a coolant/irrigation. Dental units do not deliver sterile water even when equipped with independent water reservoirs because the water lines cannot be sterilized. Delivery devices (e.g., bulb syringe or sterile, single-use disposable products) should be used to deliver sterile water. Precautions during a “boil-water” advisoryDuring a “boil-water” advisory, patients should not be treated using water delivered from a dental unit that uses the public water system. Patients should rinse with bottled water until the boil-water advisory is cancelled. Also tap water should not be used to dilute germicides, or for hand hygiene unless the water has been brought to a rolling boil for at least one minute and cooled before use. *Biofilm is a mass or layer of live microorganisms attached to a surface.Author bioLeslie Canham is a dental speaker and consultant specializing in infection control and OSHA compliance. She has more than 36 years of experience in dentistry. Canham is the founder of Leslie Canham Seminars, providing in-office training, mock inspections, consulting, and online seminars and webinars to help the dental team navigate state and federal regulations. Reach Canham at (888) 853-7543 or Leslie Canham.References1 Centers for Disease Control and Prevention. Guidelines for Infection Control in Dental Health-Care Settings 2003. MMWR 2003;52(No. RR-17): 28-30.2 Molinari J. Harte J. Practical Infection Control in Dentistry. 3rd Edition. Baltimore, MD: Lippincott Williams and Wilkins, 2009. Print.