Ensuring Water Quality in Dental Care: Importance of Dental Unit Waterline Testing and Maintenance
In my day-to-day visits to dental practices and conversations with staff, one crucial but often overlooked area of infection prevention and control is the water quality in dental unit waterlines (DUWLs). Dental unit waterline testing plays a vital role in preventing the transmission of pathogenic organisms from water used for dental procedures to patients and, incidentally, to dental practitioners.
In this blog post, I will provide a primer on dental unit waterline testing and maintenance presenting recent evidence justifying the importance of testing and maintenance to patient and staff safety.
Understanding Dental Unit Waterlines
Dental unit waterlines (DUWL) are thin plastic tubes that deliver water to dental equipment such as high and low-speed drills, air-water syringes, ultrasonic scalers and water bottle tanks (Lizardo et al., 2019). This water is used to cool and irrigate oral tissue during hygiene and restorative dental procedures. However, due to their narrow shape, ambient temperature, moist environment, and suitable width, DUWLs are prone to biofilm formation and are challenging to remove due to the tubes’ low water flow rate (Lizardo et al., 2019). The primary bacteria responsible for biofilm formation in DUWLs are Legionella Pneumophilia and Pseudomonas Aeuriginosa (Bayani et al., 2023). The sequence of events for these bacteria is that they first adhere to the hard inner surfaces of the tubes, then form microcolonies, and eventually, once their populations are significant enough, they form biofilms (Bayani et al., 2023).
The source of these bacteria is often the water supply to the DUWLs, which can cause the number of microorganisms, including fungi, bacteria and some viruses, to increase when the water in the tubes is stagnant for extended periods ( However, the primary bacterial burden originates from the microflora of a patient’s mouth, which becomes the salient contamination factor when DUWLs do not have or have anti-retraction valves that have been improperly maintained (Buitrago et al., 2023).
Biofilm formation in these lines can cause cross-infection via aerosols during cooling, spraying and ultrasonication, which can pose a severe threat to the health of patients and cause severe respiratory tract infections, especially among those patients who are immunocompromised (Dahlen, 2021; Lizardo et al., 2019).
A recent systematic review and meta-analysis of over 700 studies related to the contamination of DUWLs by Bayani and Colleagues (2023) found a high reported prevalence of bacterial biofilm, indicating the need for regular monitoring and rigorous, evidence-informed and consistent disinfection protocols (Bayani et al., 2023).
Developing a Dental Unit Waterline Testing and Management Program
- Plan Your Protocol
As you start to plan your protocol, review the public health guidelines and standards for testing and disinfecting dental unit waterlines in your province or territory and the recommendations or standards set by your respective professional dental or hygiene college. For instance, the IPAC Standards of Practice of the Royal College of Dental Surgeons of Ontario (RCDSO) suggest purging waterlines for two minutes at the beginning and end of each day, along with running handpieces for at least 20 seconds between patients to eliminate any microbial contamination. However, these standards do not provide guidance on water testing or disinfection measures. The IPAC Guide from the College of Dental Hygienists of Ontario suggests following the manufacturer’s guidelines for testing, maintenance, and preventative maintenance of lines, but nothing beyond that. These guidelines and standards serve as a starting point for developing a comprehensive standardized monitoring and testing program for dental unit water lines. When designing the plan for your dental unit waterline testing and management policy and program, look at other non-Canadian resources like the Centre for Disease Control, as they have established a threshold value for biofilm in dental unit waterlines, which can provide more specificity to your program objectives and goals. Reviewing these guidelines will also assist you in coming up with a waterline maintenance protocol, which includes daily waterline maintenance, monitoring and shock treating.
- Find a Suitable Water Testing System
In the field of dentistry, there are numerous water quality testing products available in the marketplace. Each product has its advantages and disadvantages, ranging from cost to ease of use. However, in my experience, the issue portends less to the selection of the product, which is essential, but to staff familiarity, knowledge and comfort with using the product.
Most clinical staff I speak with about water quality testing need clarification about the product they are using, whether they are using it correctly, and what the test results mean. Additionally, when asked what actions to take if the test results show higher than acceptable numbers of microbes, the staff often need clarification about what to do next. These are common concerns among dental staff.
To investigate this phenomenon, a retrospective study was conducted by Buitrago and Colleagues in 2023 found that out of the 4,093 test results collected from 137 dental clinics, 859 tests failed, but of those 859 failed tests, only 60 (7%) prompted a retest within two weeks by the staff. Even after re-testing, almost 50% of the results had a heterotrophic plate count above the acceptable 500 CFU/ml threshold. The results of this retrospective study demonstrate a profound lack of staff knowledge and training about what measures to take when a water test result exceeds the established threshold.
- Educate
Once you select a reliable dental unit waterline testing system, staff will need to be trained on how to take and interpret a water sample, use the testing system, and what to do if a sample returns as a failure. This training could be provided by the company representative from the product you selected, through online modules, or with a consultant from IPAC Consulting.
Sampling and testing, carried out by knowledgeable and informed dental staff using reliable testing kits and able to correctly interpret the results, can provide a snapshot of the number of bacteria and other microbes in the dental unit waterlines and provide valuable insights to make well-informed decisions on whether further action is necessary.
- Act
The next step is to establish a monitoring program. If there is a recommended frequency suggested by the manufacturer of the water testing kit you select, then follow that. Otherwise, the most common sampling frequency is monthly.
If one of the water testing results shows higher than acceptable CFUs/ml based on your testing kit parameters, it is essential to know what to do next. As part of the education process, many water testing kit instructions will guide what to do in the event of a failed test. If the water testing kit product contains these instructions, follow them. Otherwise, the best evidence-based approach is to shock the waterlines using some form of chemical disinfectant, which is distinct from evacuation line cleaners or treatment products for bottled water. When selecting a product for DUWL treatment, ensure that it mentions the words “shock treatment” or the word “shock” in the description. These shock disinfectants’ main active ingredients are non-ionic surfactants, sodium lauryl sulphates, which synergistically remove many bacteria, and organic and inorganic soils, including biofilms (Umer et al., 2022). Whatever shock treatment product you choose, always follow the manufacturer’s instructions for preparation and use.
Waterline maintenance is the final, and most important step in the process. Just like patients come in for routine cleanings to prevent oral health issues from developing, or catching them in their early stages before they become a serious health issue, the same goes for dental unit waterline maintenance. This involves line purging at the interval recommended by your professional college or public health authority, manual line cleaning using a lumen brush, to prevent biosolids from accumulating in the lines, anti-retraction valve maintenance and routine disinfection of waterlines to keep the CFUs/ml low, using an approved product. As for any products used in dentistry, always follow the manufacturers recommendations and instructions for use. This particularly applies to the disinfectant product. All water disinfectants have an active time, and should always be replaced before the conclusion of that active time to ensure continual disinfection.
Dental unit waterline testing and maitenance are vital components of quality assurance of patient safety in dental care. By using established guidelines to develop regular testing and maintenance protocols, and dental professionals can protect patients’ and dental staff’s health and safety. Incorporating a comprehensive waterline maintenance protocol at your pratice further demonstrates your commitment to providing high-quality and safe dental care and cultivating a safe environment for everyone involved.
References
Bayani, M., Raisolvaezin, K., Almasi-Hashiani, A., & Mirhoseini, S. H. (2023, March 18). Bacterial biofilm prevalence in dental unit waterlines: a systematic review and meta-analysis. BMC Oral Health, 23(1). https://doi.org/10.1186/s12903-023-02885-4
Buitrago, J. M., Kolbe, R. J., & Siqueira, M. F. (2023, November 15). Dental unit waterline testing practices: an 11-Year retrospective study. BMC Oral Health, 23(1). https://doi.org/10.1186/s12903-023-03590-y
Dahlen, G. (2020, December 21). Biofilms in Dental Unit Water Lines. Oral Biofilms, 12–18. https://doi.org/10.1159/000510195
Lizzadro, J., Mazzotta, M., Girolamini, L., Dormi, A., Pellati, T., & Cristino, S. (2019, January 24). Comparison between Two Types of Dental Unit Waterlines: How Evaluation of Microbiological Contamination Can Support Risk Containment. International Journal of Environmental Research and Public Health, 16(3), 328. https://doi.org/10.3390/ijerph16030328
Umer, F., Khan, M., Khan, F. R., & Tejani, K. (2022, June). Managing dental unit waterlines: a quality improvement programme. BMJ Open Quality, 11(2), e001685. https://doi.org/10.1136/bmjoq-2021-001685
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