CDA Essentials 2019 • Volume 6 • Issue 6

37 Issue 6 | 2019 | S upporting Y our P ractice Dr. Nita Mazurat recently retired as associate professor in the Department of Restorative Dentistry, College of Dentistry, at the University of Manitoba where she was director for Regulatory Compliance, including infection prevention and control. She is the first Canadian dentist to be a member of the CSA Technical Committee on Sterilization and participated in the development of the 2018 National Standard of Canada for medical device reprocessing (CAN/CSA-Z314-18) . Maintaining Optimal Quality TreatmentWater in Dental UnitWaterlines The Challenge Thanks to research that has advanced our understanding of water quality in dental units, we now recognize the factors that contribute to the development of biofilms in dental unit waterlines (DUWL). We know that biofilms found in DUWL are structured communities with sophisticated feedback mechanisms. We appreciate how growth of biofilm is influenced by the dental unit’s design and use—in the size and composition of its waterlines and the way water flows through those lines, with little or no interaction with biofilm. We understand that using negative pressure to prevent an air/water syringe or handpiece from dripping when not in use can contaminate water in DUWL with microbes from patient “suck back.” And finally, we are aware that stagnant water in unused sections of tubing, also known as “dead legs,” can promote biofilm growth and contaminate the water supply. We also better understand the requirements for maintaining DUWL, including the role of waterline flushing and cleaning, and the efficacy of various disinfectants. In particular, use of validated continuous waterline disinfectants while treating patients has been shown to be safe for patients with no deleterious effects on dental materials. And finally, water quality monitoring now can be accomplished in-office using affordable, convenient and validated methods. Formation of Biofilms Why do DUWL become colonized by biofilms? Most bacteria that occur in nature survive as biofilms in environments where there is moisture and a surface for attachment. Therefore, it is not surprising that bacteria found in water would colonize DUWL and form biofilm. Organic particles from water adsorb onto the inner surface of the narrow diameter plastic tubing and form a conditioning layer that makes it easier for bacteria to colonize. Other factors also aid in colony formation. When waterlines are used intermittently (e.g., between evenings, weekends and vacation times) bacterial colonies have time to grow, potentially doubling every 4–20 minutes. Water lines are designed to use laminar flow, meaning that the water moves mainly through the centre of the tubing to provide the operator with consistent pressure; however, this results in minimal disturbance to biofilm colonies. Dissolved minerals in water such as calcium and magnesium—the main determinants of water hardness—can be a food source for certain organisms and can strengthen crosslinks in the biofilm structures. 1 Nita Mazurat, DDS, MSc Theviewsexpressedarethoseoftheauthorand donotnecessarilyreflecttheopinionsorofficial policiesoftheCanadianDentalAssociation. Infection Prevention and Control at the Dental Office