Dental unit waterline (DUWL) maintenance and monitoring remain an area of concern for dental facilities. Agencies such as the CDC, FDA, and ADA have issued guidance for dental offices on maintaining DUWL. It is the recommendation of these agencies that waterlines are to be treated with a disinfectant/chemical and then monitored (tested) to ensure the water quality meets the EPA safe drinking water standards of less than 500 colony forming units per milliliter of water.
Many dental settings use water from the municipal water supply through office plumbing. Other ways to deliver water to the dental unit are through self-contained bottles, in-line microfilter, cartridges and central systems. Dental units carry the water through the thin plastic tubing (hoses) that are small diameter tubes that deliver water to the air/water syringe, handpieces, and ultrasonic scalers to the patient’s mouth. Due to the nature of the tubing being small and the material the lines are made of, they can become colonized with microorganisms. These microorganisms can include bacteria, fungi, and protozoa. The most common bacteria found in DUWL are Legionella, Pseudomonas, nontuberculous Mycobacterium, staphylococcus and streptococcus. This colony of microorganisms is called biofilm.
Biofilm is described as a thin, slimy film of bacteria that sticks to the inside of tubing and can form in any water environment. Biofilms form due to the long, small-diameter tubing, low flow rates and frequent periods of stagnation. The biofilm must be treated with a chemical disinfectant to be destroyed, making the water safe to deliver to patients.
There are several ways to treat biofilm. Contact the manufacturer of your dental units to find out which method(s) of treatment would work best for your dental unit. They may recommend a self-contained water system, an in-line filter, or a combination of these. Self-contained water systems are used with shock treatment, tablets, and straws with either distilled or potable water. Utilizing distilled or potable water alone in the self-contained system is not enough. The water must be treated to ensure safe drinking water standards are met. In-line filters have disinfectants in the filters to control the biofilm; hence delivering safe water to patients.
There have been outbreaks where illness has occurred due to untreated DUWL. Those cases have been reported in Georgia and California where pediatric dental patients developed Mycobacterium abscessus after pulpotomy procedures. The infections required hospitalization of several children ranging in age from 4-8. The infections were linked to the untreated contaminated water from dental units. Treatments ranged from IV antibiotics to surgery for some of the children. Georgia now requires that dental offices test waterlines quarterly. Washington also requires quarterly testing.
The steps in maintaining and delivering safe water to your patients are to shock, treat, test and then maintain. Shock is the use of a strong disinfectant/cleaner that is used to attack and reduce biofilm. Shock must be done before starting an independent water reservoir system or any other method intended to improve incoming water quality. Shock frequency would be determined in following manufacturers’ instructions for use from the dental unit or product used.
After your lines have been shocked, treatment will be necessary. Treatment occurs by using tablets, straws, cartridges, in-line filters, and central systems. Treatment is a continuous disinfectant that is used daily.
Once you have determined the treatment that is best for your facility, CDC recommends that you consult with the manufacturer on the frequency of monitoring (testing). However, CDC does recommend routine monitoring. Monitoring dental unit water quality helps identify any problems in performance or adherence with maintenance protocols. It also provides documentation of compliance. Monitoring is the only way to ensure your product is working for you and that safe drinking water standards are met. Association of Dental Safety, formerly OSAP, recommends that testing of DUWL be done at least quarterly. ADA also recommends routine monitoring of DUWL. If the manufacturer issues no guidance for monitoring, the facility should monitor (test) on a routine basis. Best practice would be to test monthly until two passing tests are achieved, then you can move to quarterly. This was stated in OSAP’s white paper on dental unit waterlines.
Testing of DUWL can be performed by using commercial self-contained test kits or commercial water-testing laboratories. If your water quality doesn’t meet drinking water standards, actions should be taken to correct the issue. Those actions would include a shock treatment followed by treatment (straws, tablet, in-line filter) and then re-testing immediately after treatment. However, always consult with the manufacturer of the product or dental equipment for guidance.
Dental unit water that is not treated is likely to contain high numbers of microorganisms and most likely will not meet drinking water standards. Not treating DUWL is inconsistent with accepted infection control principles. Dental facilities should work with equipment manufacturers to ensure their water treatment meets or exceeds the standards set by the EPA for safe drinking water. Remember the steps in delivering safe drinking water are:
Having a safe dental unit waterline program is a necessity in dental practices. A program would be built on consistent, documented processes: shock, treat, routine testing. These processes should align with the manufacturer instructions and meet the established standard of < 500 CFU/mL for routine dental treatment. Staff training must take place to ensure the process is followed. Accountability helps prevent contamination of DUWL and provides safe care for every patient.
