Snaking in and around dental chairs, dental unit waterlines (DUWLs) are the arteries of every practice, delivering essential water to handpieces and scalers and enabling a consistent number of patients to be treated every day. Because of their importance, diligent maintenance is required to keep them functional – and safe.
Waterborne pathogens can be acquired through unclean drinking water, from contact with animals or their environment, or through person-to-person transmission. In the dental practice, contaminated DUWLs can release pathogens directly to patients through inhalation or wounds, increasing the risk of infection. But research has also found a potential association between DUWL contamination, respiratory illness and the perceived risk for dental professionals.[i] A deeper understanding is needed to better protect members of the dental team.
Perilous pathogens
Most of the organisms isolated from DUWL are of low pathogenicity.i However, a few of the most common waterborne microorganisms that can cause illness include:
- Legionella
- coli
- Campylobacter
- Salmonella
- Pseudomonas aerugunosa
- Giardia
- Cryptosporidium[ii]
With a reported prevalence between 0-68%, legionella is notable and varies wildly in DUWLs.i It grows at temperatures of 25-50 degrees Celsius, especially in stagnant water, and can cause the form of pneumonia known as Legionnaire’s disease – it has been frequently evaluated for its role in infecting dental professionals.[iii]
Identifying the source
Microbial contamination in DUWLs may originate from both waterborne pathogens but also germs from a patient’s oral cavity due to the suck-back of saliva.iii In cases of the latter, microbes like Porphyromonas gingivalis, which increases the build-up of bacterial plaque, can enter the water supply. Similarly, dental turbines operate with fast rotations; when slowing down the tip of the instrument draws organic material from the oral cavity inside, creating back-contamination. Whilst handpieces may feature anti-retraction valves, there can on occasion be failute, and these fluids may be sprayed onto the next patient’s oral mucosae, even if the handpiece has been replaced.iii
Even with comprehensive sterilisation of the handpieces, the dental unit will still be a source of pathogens if connected to a contaminated water supply. The undisturbed existence of pathogens in a DUWL leads to the formation of biofilm on the interior surface of the pipes. This is a universal problem; bacteria adhere to the surface of a substrate and are able to maintain a stable synergy among different species of microorganisms, whilst also becoming resistant to biocidal agents that is 2-3 orders of magnitude greater than that of non-adherent microbial cells – this demands tough decontamination action.
The dominant species isolated from DUWLs are Gram-negative bacteria; these are among the world’s most significant public health problems because of their ability to resist antibiotics, leading to a heightened risk of morbidity and mortality.[iv] Respiratory complications, such as asthma and Legionnaire’s disease, can be triggered or exacerbated by the production of cell wall endotoxins, of which Gram-negative bacteria is a potent source.i This is the occupational risk that dental professionals face if DUWLs are not regularly decontaminated, as the resulting bacteria can spread through the air – patients are at a much lower risk.i It has been further reported that higher rates of Legionella antibodies have been found among dental personnel than among the general public.iii
Prevention first
More than 81 million people in Europe are affected by chronic respiratory diseases, the sixth leading cause of death.[v] It is therefore paramount that correct decontamination protocols are followed to reduce the risk of respiratory diseases, protecting both patients and the dental professionals who are more consistently exposed to pathogenic transmissions.
Among the recommended practices are anti-stagnation practices to keep water circulation constant, manually flushing through all devices and instruments connected to a waterline before use, and disinfecting the water through both continuous and discontinuous treatments. The combined effect of these protocols prevents biofilm formation and the subsequent risk of infection transmission.
Ready for action
A reliable solution for water maintenance is Bioclear Daily from Dentisan. Reducing the planktonic bacteria count in water flowing through the dental unit, it is designed for daily use to disrupt biofilm formation and maintain water quality to the HTM 01-05 standard. Able to be diluted and readied in advance, prepared solutions can keep for up to 10 days in suitable plastic containers for ease of use. Ensure compliance and prevent the risk of infection with the help of Dentisan.
The association between contaminated DUWLs and the risk of respiratory illness is an alarming occupational hazard for dental professionals. An effective decontamination workflow that regularly prevents pathogen build-up keeps the dental team safe from infectious diseases for a consistent, uninterrupted working environment.
For more information about Dentisan, please visit https://dentisan.co.uk/
Book your in-practice CPD by emailing your request to the expert in your area:
For the Midlands, North Wales & North of England, contact Jenny: jenny.nixon@getinge.com
For the South of England, Wales & Channel Islands, contact Anne: anne.harris@getinge.com
For Scotland, Ireland & Northern Ireland, contact Holly: holly.dickinson@getinge.com
Author: Jenny Nixon – Business Development Dentisan
[i] Pankhurst, C.L. and Coulter, W.A. (2007). Do contaminated dental unit waterlines pose a risk of infection? Journal of Dentistry, 35(9), pp.712–720. doi:https://doi.org/10.1016/j.jdent.2007.06.002.
[ii] Ramírez-Castillo, F., Loera-Muro, A., Jacques, M., Garneau, P., Avelar-González, F., Harel, J. and Guerrero-Barrera, A. (2015). Waterborne Pathogens: Detection Methods and Challenges. Pathogens, 4(2), pp.307–334. doi:https://doi.org/10.3390/pathogens4020307.
[iii] Spagnolo, A.M., Sartini, M. and Cristina, M.L. (2020). Microbial Contamination of Dental Unit Waterlines and Potential Risk of Infection: A Narrative Review. Pathogens, [online] 9(8). doi:https://doi.org/10.3390/pathogens9080651.
[iv] Oliveira, J. and Reygaert, W.C. (2023). Gram Negative Bacteria. [online] Nih.gov. Available at: https://www.ncbi.nlm.nih.gov/books/NBK538213/.
[v] World (2025). Chronic respiratory diseases: more than 80 million affected and many more undiagnosed, warns new WHO and European Respiratory Society report. [online] Who.int. Available at: https://www.who.int/europe/news/item/12-06-2025-chronic-respiratory-diseases–more-than-80-million-affected-and-many-more-undiagnosed–warns-new-who-and-european-respiratory-society-report.
