Dental Unit Water Quality

Biofilm is a thin, slimy film of bacteria that sticks to moist surfaces, such as those inside dental unit waterlines. Biofilm occurs in dental unit waterlines because of the long, small-diameter tubing and low flow rates used in dentistry, the frequent periods of stagnation, and the potential for retraction of oral fluids.1 As a result, high numbers of common water bacteria can be found in untreated dental unit water systems. Disease-causing microorganisms found in untreated dental unit water include Legionella, Pseudomonas aeruginosa, and nontuberculous Mycobacteria. Dental health care personnel and patients could be placed at risk of adverse health effects if water is not appropriately treated.

For all non-surgical dental treatment output water, dental health care personnel should use water that meets environmental protection agency regulatory standards for drinking water (i.e., ≤500 colony forming units (CFU)/mL of heterotrophic water bacteria).2 Consult with the dental unit manufacturer for appropriate methods and equipment to maintain the quality of dental water. Commercial devices and procedures designed for this purpose include:

  • Self-contained water systems (e.g., independent water reservoir) combined with chemical treatment (e.g., periodic or continuous chemical germicide treatment protocols).
  • Systems designed for single-chair or entire-practice waterlines that condition or treat incoming water to remove or inactivate microorganisms.
  • Combinations of these methods.

Available products to treat waterlines include tablet systems, continuous release straws and cartridges, initial and periodic shock treatments, and centralized systems. All products and systems must be used and maintained according to the manufacturer instructions for use (IFUs). If you have questions about the IFUs, contact the manufacturer of the treatment product or device that you are using.

For surgical procedures, sterile saline or sterile water should be used as a coolant/irrigant. Conventional dental units cannot reliably deliver sterile water even when equipped with independent water reservoirs containing low-microbial or sterile water because the water-bearing pathway cannot be reliably sterilized. Appropriate delivery devices (e.g., bulb syringe; sterile, single-use disposable products; or sterile water delivery systems that bypass the dental unit by using sterile single-use disposable or sterilizable tubing) should be used to deliver sterile water during surgery.

For all non-surgical pulpal and endodontic procedures, clinicians can also consider using sterile irrigants or antimicrobial solutions.3-6


  1. Guidelines for Infection Control in Dental Health-care Settings – 2003. MMWR2003; 52(No. RR-17):1–66.  Accessed September 22, 2022.
  2. US Environmental Protection Agency. National Primary Drinking Water Regulations. Accessed September 22, 2022.
  3. American Academy of Pediatric Dentistry, Guidelines for Infection Control,–recommendations/infection-control/. Accessed September 22, 2022.
  4. American Academy of Pediatric Dentistry, Pulp Therapy for Primary and Immature Permanent Teeth, Accessed September 22, 2022.
  5. American Association of Endodontists, AAE Position Statement on Vital Pulp Therapy,. Accessed September 22, 2022.
  6. Organization for Safety, Asepsis and Prevention (OSAP). Dental Unit Water Quality: Organization for Safety, Asepsis and Prevention White Paper and Recommendations– 2018. 1, Issue 1, 2018 October 31.
  7. Hatzenbuehler LA, Tobin-D’Angelo M, Drenzek C, Peralta G, Cranmer LC, Anderson EJ, Milla SS, Abramowicz S, Yi J, Hilinski J, Rajan R, Whitley MK, Gower V, Berkowitz F, Shapiro CA, Williams JK, Harmon P, Shane AL. Pediatric Dental Clinic-Associated Outbreak of Mycobacterium abscessus Infection. J Pediatric Infect Dis Soc. 2017 Sep 1;6(3):e116-e122. doi: 10.1093/jpids/pix065. PMID: 28903524.
  8. Singh J, O’Donnell K, Nieves DJ, Adler-Shohet FC, Arrieta AC, Ashouri N, Ahuja G, Cheung M, Holmes WN, Huoh K, Tran L, Tran MT, Pham N, Zahn M. Invasive Mycobacterium abscessusOutbreak at a Pediatric Dental Clinic. Open Forum Infect Dis. 2021 Apr 15;8(6):ofab165. doi: 10.1093/ofid/ofab165. PMID: 34113683; PMCID: PMC8186244.
  9. Pérez-Alfonzo R, Poleo Brito LE, Vergara MS, Ruiz Damasco A, Meneses Rodríguez PL, Kannee Quintero CE, Carrera Martinez C, Rivera-Oliver IA, Da Mata Jardin OJ, Rodríguez-Castillo BA, de Waard JH. Odontogenic cutaneous sinus tracts due to infection with nontuberculous mycobacteria: a report of three cases. BMC Infect Dis. 2020 Apr 21;20(1):295. doi: 10.1186/s12879-020-05015-5. PMID: 32316920; PMCID: PMC7171849.
  10. Ricci ML, Fontana S, Pinci F, et al. Pneumonia associated with a dental unit waterline. Lancet2012; 379(9816):684.
  11. American Academy of Pediatric Dentistry, Use of Vital Pulp Therapies in Primary Teeth with Deep Caries Lesions, Accessed September 22, 2022.