Dental Unit Waterlines

Dental Unit Waterlines

Dental Unit Waterlines consist of any line or tubing connected to the dental unit or chair that water runs through to instruments or items that enter the patient’s mouth. This includes high- and low-speed handpieces, prophylaxis angles, air abrasion devices, air/water syringes, and ultrasonic scalers. Studies have shown that dental waterlines can become colonized with bacteria, fungi, and protozoa.

These organisms can form a layer on the internal channel of the waterlines, which is challenging to remove. You may be more familiar with the term “biofilm,” which is the more technical name for this stubborn layer of organisms. The organisms can break off from the biofilm and enter the patient’s mouth during irrigation, with the potential to cause an infection, depending on the procedure that was performed, among other factors.

Recent History and Background

According to the Centers for Disease Control and Prevention (CDC), there have been documented cases of infections transmitted to patients from dental unit waterlines. In 2011, an 82-year-old woman in Italy was diagnosed with legionellosis and died two days later. The only known risk factor for exposure were two appointments. Molecular testing identified the dental unit waterline as the source. In 2015, 24 children who underwent pulpotomies developed severe infections caused by Mycobacterium abscessus.

All affected children were hospitalized, 17 patients required surgical excision, and 10 received outpatient intravenous (IV) antibiotics. M. abscessus was identified in the dental unit water. Molecular testing determined the water samples, and patient specimens were indistinguishable. In other words, there wasn’t any doubt that the dental unit waterlines were the source of the infections.

Another more significant outbreak in size occurred in 2016 among more than 60 children that underwent a pulpotomy at a dental practice in California. The CDC investigation determined the practice used untreated water from the dental unit for irrigation that resulted in the M. abscessus infections. These infections highlight the need to adhere to the CDC and the American Dental Association (ADA) recommendations for dental unit waterlines.

The CDC published the Guidelines for Infection Control in Dental Health-Care Settings in 2003. More recent publications are still based on this guideline and refer the reader to the 2003 edition for additional information. The American Dental Association (ADA) concurs with the CDC recommendations. Another useful resource is the Organization for Safety, Asepsis, and Prevention (OSAP). Although the ADA and OSAP require memberships to access the entire site, some information is available on both sites, even if you aren’t a member.

How to Keep Patients Safe

The CDC, ADA, and OSAP recommend using water that meets the environmental protection agency regulatory standards for drinking water, which is < 500 colony forming units (CFU)/mL for non-surgical dental water irrigant/coolant. The drinking water standard is the maximum level of organisms contained in dental waterlines. The most prudent stance is to keep the microbial count as low as possible.

Utilize a Self-Contained Water System

This is also known as an independent water system or reservoir. This type of system provides water to patients that is filled and maintained by the dental practice staff, meaning the practice has control over the quality of the water supplied to patients. Additionally, self-contained water systems provide a method to chemically disinfect the waterlines and use water of known microbiological quality. Studies have shown that the organism count can reach about 200,000 colony forming units (CFU)/mL within five days after the installation of new dental unit waterlines.

Consult With Dental Unit Manufacturer

During your phone call or meeting, determine the best methods and equipment to maintain the recommended water quality levels by ensuring you avoid using chemicals that may be harmful to your system. There are several methods to disinfect dental unit waterlines continuously. Disinfectant ‘straws’ that can be placed into the chairside bottle and replaced only once or twice a year, and tablets that are put into the chairside container daily or more often if the bottle is refilled during the day. There are also periodic disinfection options that involve purging the lines, adding a chemical disinfectant to the water reservoir, allowing the disinfectant to remain in the lines and reservoir for a specified amount of time followed by copious flushing.

Most disinfectant product manufacturers recommend ‘shocking’ the water system as an initial treatment. However, when switching brands of disinfectants, consult the manufacturer to determine if the new disinfectant manufacturer recommends shocking the system. Disinfection of the dental unit should occur even if distilled, deionized, or reverse osmosis water is used to fill the water reservoirs for the reasons previously stated.

Follow Product Manufacturer’s Recommendations

Monitor water quality by referring to the product manufacturer’s suggestions for the frequency of culturing water in the dental units. There are in-house water testing kits as well as kits that can be sent off to a lab that tests water quality. It is important to note that water cultures should never be sent to a lab that isn’t certified for testing water.

Run Water and Air After Each Patient

This practice should be implemented for a minimum of 20-30 seconds from any device connected to the dental water system that enters the patient’s mouth. According to the CDC, studies of high-speed handpieces using dye expulsion have shown the potential for retraction of oral fluids into internal components of the handpiece. This means there is a possibility that saliva and other material can be expelled intraorally into the next patient’s mouth. Additionally, studies have shown that viral DNA and the viable virus can be retained inside high-speed handpieces and prophylaxis angles.

Although studies haven’t been performed on other types of handpieces or scalers, these studies form the basis of these recommendations. The intent of running water and air for 20-30 seconds is to flush out any material that may have entered the turbines and air and waterlines. This recommendation should be incorporated between patient activities since the handpiece, etc. must remain connected until air and water are discharged through the device.

CDC Dental Infection Control Guidelines: Boil Water Advisory

This resource also contains a section for “boil water” advisories, which states the following:

  • Do not deliver water from the public water system to the patient through the dental operative unit, ultrasonic, scalar or other dental equipment that uses the public water system
  • Do not use water from the public water system for dental treatment, patient rinsing, or handwashing
  • For handwashing, use antimicrobial containing products that do not require water for use (e.g., alcohol-based hand rubs). If hands are visibly contaminated, use bottled water, if available, and soap for handwashing or an antiseptic towelette

Once the ‘Boil Water’ Advisory Is Discontinued:

  • Follow the guidance given by the local water utility regarding adequate flushing of waterlines. If no direction is provided, flush dental waterlines and faucets for 1–5 minutes before using for patient care
  • Disinfect dental waterlines as recommended by the dental unit manufacturer

In summary, as stated by the ADA: “strict adherence to maintenance protocols is required to sustain the quality of dental unit water,” which will keep dental patients safe and your practice out of the headlines.



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