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Why Testing for Legionella in Dental Water Lines Important?

According to HTM 01-05: Decontamination in primary care dental practices ‘Registered Managers of dental practices have an overriding general duty of care under the Health and Safety at Work Act 1974’. Part of this duty of care is ensuring that the water supply, storage and distribution services should comply with the best practice guidance given in:

Legionella bacteria and other organisms live in water supplies; some are completely harmless, whilst others such as Mycobacteria spp and Pseudomonads can cause disease.   Dental Practices have not only their domestic water system to look after but also their dental water line systems which can pose greater risks to patients and staff.  Dental water lines are prone to developing ‘biofilm’ on the inside of the tubes and provide ideal conditions for bacteria to survive.

Remember, water in dental water lines is going into patients mouths. It comes into contact with open wounds as a result of oral surgery and is swallowed by patients. There is also potential for occupational risk to the dental team from exposure to contaminated dental unit waterlines aerosols. Likewise vulnerable patients such as those suffering from chronic respiratory diseases, alcoholics, diabetics and immuno-compromised patients may potentially be at increased risk of respiratory infection or colonisation from inhaling contaminated aerosols during dental treatment.

In the UK, dental practices are required to perform risk assessments and to draw up a written waterline management scheme and Legionella risk assessment. The registered managers of dental offices must also ensure that recommendations following the risk assessment are closely followed. Dental offices are also required to fit anti-retraction valves to water and air lines and to control Legionella within the water system.

In cases which involve contracting infections after a visit to a dental practice, the main culprit is usually the dental unit waterlines which can facilitate the growth of bacteria. The main reason behind this is that water in the dental practice is not used continuously. Instead, water is used in a start and stop basis, usually when the dentist is working or when the patient needs to rinse his mouth. That creates stagnant water.

When a biofilm consisting of microbes, fungi and bacteria forms along the waterlines, decontamination can prove to be a difficult task. This is because the microbes in the biofilm feed and protect each individual member. The outer layer can be killed but the inner layer can survive.

One difficulty faced by dentists in keeping waterlines safe is the fact that there is no single approach that is deemed to be truly effective. Most dental practices use chemicals which are either used intermittently or continuously along with disinfectant cartridges and filters.

Testing for Legionella, Mycobacteria spp and Pseudomonads in water lines will provide you with peace of mind that your control measures continue to be effective.