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Dental Unit Waterlines


Dental Unit Waterlines: Dental Unit Water Line Fact Sheet

The oral health professions have traditionally assumed responsibility for assessing and improving the quality of healthcare provided to patients. For example, today oral health workers routinely wear disposable gloves masks, protective garments, and eyewear, and sterilize instruments - all generally initiated since baby boomers first started visiting the dental offices.

Similarly, oral health staff members throughout the country should be familiar with the issue of dental unit waterline contamination and be prepared to discuss the issue with their patients. Following is the "What , Where , When , Why and How"

What - Dental unit waterline contamination consist of slime-producing bacteria, fungi and protozoans. These microorganisms colonize and replicate on the interior surfaces of waterline tubing, inevitably resulting in adherent heterogeneous microbial accumulations termed "biofilms."

Where - Microbial biofilms are ubiquitous in nature and can be found virtually anywhere there is moisture and a suitable solid substrate for attachment. In dentistry, biofilms form on the walls of small-bore plastic tubing in dental units which deliver coolant water for high-speed dental hand-pieces, air-water syringes, and ultrasonic scalers.

When - Water coming into buildings from city water supplies or wells is not sterile and contains a number of waterborne bacteria and trace amounts of nutrients that may support the growth of bacteria. Inevitably, some bacteria attach to, and accumulate on, the inside of the lines forming a biofilm. Once formed, biofilms serve as a reservoir significantly amplifying the numbers of free-floating microorganisms in the water exiting the waterlines.

Why - The biofilm "issue" is important to understand. Although there is no currently definable public health problem, the presence in dental unit waterlines of clinically proven human pathogens including Pseudomonas, Legionella, and nontuberculosis Mycobacterium species supports the dental industry's objective of improving water quality. This objective specifies the development and validation of standard protocols for the maintenance and monitoring of water delivered to patients during nonsurgical dental procedures equivalent to an existing quality assurance standard utilized in hemodialysis units.

How - The American Dental Association (ADA) recently published a statement on dental unit waterlines that challenges the industry to produce systems that can reduce the level of bacteria used in dental treatment water to 200CFU/ml or fewer by the year 2000. There are several commercially available options for improving dental unit water quality including independent water reservoirs, chemical treatment regimens, daily draining and air purging regimens, and point of use filters. Preliminary data suggest that some combination of these strategies will be necessary to control biofilm formation and achieve the desired level of water quality. To date, however, there are insufficient data to establish the effectiveness of all available methods as used in the dental office. It is important to ensure that any sterile water system or device marketed to improve dental water quality has received Food and Drug Administration (FDA) clearance. Research is currently underway to validate other proposed water treatment methods and water quality monitoring indicators.
In the interim, there are many steps oral health practitioners can take to improve the quality of dental unit water. However, please note that practitioners should always consult with manufacturer of their dental units before initiating any waterline treatment protocol.

  1. Follow current OSAP, ADA, and CDC recommendations to flush lines for several minutes each morning. Flush handpieces with air/water for 20 to 30 seconds between patient appointments. Installing sterilized handpieces and sterile or disposable syringe tips after flushing will reduce cross-contamination.
  2. Always obtain and follow the dental unit manufacturer's recommendations for treating dental unit waterlines. Implementing protocols not recommended by the unit manufacturer could cause equipment damage and void warranties.
  3. If recommended by the dental unit manufacturer, install and maintain antiretraction valves to prevent oral fluids from being drawn into dental waterlines.
  4. Avoid heating dental unit water. While it was common to heat water to increase patient comfort, warming the water may amplify biofilm formation and select organisms pre-adapted to growth in a human host.
  5. Consider using a separate water reservoir system to eliminate the inflow of municipal water into the dental unit. In addition to having better control over the quality of the source water used in patient care, it would eliminate interruptions in dental care when "boil-water" notices are issued by local health authorities. Contact the manufacturer of the dental unit for a compatible system and treatment protocols before undertaking this step.
  6. Use sterile solutions for all surgical irrigations. Additionally, ensure that only heat-sterilized/sterile-disposable bulb syringes or sterile water delivery devices are employed to deliver the sterile water.
  7. Educate and train oral healthcare workers on effective treatment measures to ensure compliance and minimize risks to equipment and personnel.
  8. Monitor scientific and technological developments in this area to identify improved technical approaches as they become available.
  9. Cooperate with the oral healthcare industry to develop and validate standard protocols for maintaining and monitoring dental unit waterlines.
  10. Because insufficient data currently exist to establish the effectiveness of all available methods as used in the dental office, it is important to ensure that any sterile water system or device marketed to improve dental water quality has been cleared for market by the U.S. Food and Drug Administration (FDA).

Staff also may consider utilizing a "Message to Patients."


This fact sheet is presented to you by the American Dental Hygienist's Association and the Organization for Safety and Asepsis Procedures (OSAP). It was prepared with the assistance of OSAP Editorial Team members Nancy Andrews, RDH; Mary Govoni, CDA,RDH; Therese Long; Chris Miller, PhD; John Molinari, PhD, John Tullner, DDS; Phil Westover; and Jeff Williams, PhD, MRCVS.


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