Maintaining Dental Unit Water Lines
Compiled by Kristin Hohman
The problem of microbial contamination in dental unit waterlines is the result of how water is used during routine dentistry and the design of the dental equipment itself. Factors including small-diameter waterlines, low flow rates, long periods of stagnation, improper waterline termination, and even occasional backward contamination from the patient to the delivery system all contribute to microbial contamination.
The unfortunate reality is that even quality input water can quickly become contaminated in dental unit waterlines. Even a single microorganism that survives filtration and chemical treatment can replicate exponentially. As such, microbiological contamination of dental unit waterlines is a challenging issue that must be addressed rigorously.
COVID-19 renewed the dental industry’s focus on infection control and mitigation. Even though the pandemic did not exacerbate dental unit waterlines (DUWL) issues, it should still cause practices to be more vigilant.
The Centers for Disease Control and Prevention (CDC) laid out safety measures in its 2003 Guidelines for Infection Control in Dental Health-Care Settings. These include1:
- Use water that meets Environmental Protection Agency regulatory standards for drinking water (ie, ≤ 500 CFU/mL of heterotrophic water bacteria) for routine dental treatment output water
- Consult with the dental unit manufacturer for appropriate methods and equipment to maintain the quality of dental water
- Use sterile saline or sterile water as a coolant/irrigant when performing surgical procedures
Commercial devices and procedures designed for dental units include2:
- Self-contained water systems (eg, independent water reservoir) combined with chemical treatment (eg, periodic or continuous chemical germicide treatment protocols)
- Systems designed for single-chair or entire-practice waterlines that purify or treat incoming water to remove or inactivate microorganisms
- Combinations of these methods
Whether dental operatories are plumbed directly to municipal water supply lines, utilize independent bottle systems, or have a water filtration system installed, the following protocols and guidelines should be observed at all times for dental waterline maintenance3:
- Discharge air and waterlines for a minimum of 20 to 30 seconds after each patient, as recommended by the CDC. This procedure is intended to flush out patient material that might’ve entered the handpiece turbine, air, or waterlines.
- Don’t use waterline heaters, as they serve to increase the growth rate of any microorganisms that might be present in the lines.
- Never use water from a standard dental delivery system during surgical procedures. Instead, use sterile water or saline delivered by sterile means, such as autoclavable bulb syringes or autoclavable or disposable sterile tubing.
- Monitor water quality throughout the operatory environment at least quarterly by submitting water samples to a laboratory for heterotrophic plate count (HPC) testing, or by using an in-office testing product, to ensure compliance with water-quality standards of less than 500 colony-forming units (CFU) of bacteria per milliliter, as recommended by the CDC.
- If using any type of water filtration system—whether plumbed directly to the dental delivery unit or for filling dental bottles—it’s important to follow the manufacturer’s instructions for use.
1. Key recommendations for dental unit water quality in dental settings. Centers for Disease Control and Prevention. Updated June 18, 2018. Accessed May 20, 2021. https://www.cdc.gov/oralhealth/infectioncontrol/summary-infection-prevention-practices/dental-unit-water-quality.html
2. What can be done to ensure dental unit water quality? Centers for Disease Control and Prevention. Updated March 25, 2016. Accessed May 20, 2021. https://www.cdc.gov/oralhealth/infectioncontrol/faqs/dental-unit-water-quality.html
3. Elsenpeter R. How to maintain dental unit waterlines. Dental Products Report®. Published January 24, 2019. Accessed May 20, 2021. https://www.dentalproductsreport.com/view/maintaining-dental-unit-waterlines