It is universally agreed, and in fact reconfirmed in HTM 01-05, that the water entering patients’ mouths in a dental surgery via DUWL should be of an acceptable quality. According to HTM 01-05, ‘acceptable’ is defined as falling below 200cfu/ml, the equivalent of the European water quality standard.
As part of infection control procedures, a risk assessment of water provision is required, which should be written by a ‘competent person’ and used to identify potential issues such as excess storage capacity, temperature distribution problems, low water usage, or inappropriate materials. This risk assessment then forms the basis for creating an action plan, which addresses any of the issues that pose a potential risk to either staff or patient safety. It is essential that all staff, not just the infection control lead, have an appreciation of those procedures that might affect water hygiene and safety, and that each member of the team can interpret the appropriate guidance and perform required tasks in a competent manner.
So what constitutes the journey of the water used in practice? Where does it come from and how can the responsible internal staff ensure that it is within the required standards?
All the equipment within a practice that uses any kind of water requires constant checking and also has strict protocols with which to adhere. One of the critical factors affecting the quality of water is the extent of its usage. For example, in the case of taps used infrequently, flushing should be carried out once a week with the procedure being be fully documented and covered by written instructions. For autoclaves there is a standard which input water must meet and a requirement of reservoirs to be emptied and cleaned at the end of each day. It is not considered good practice to leave water in any machine overnight, as there is the potential for water borne pathogens to develop even in a relatively short period of time. Even the water used to clean instruments is covered in the guidance, where it specifies that instruments washed manually by ultrasonic methods or in a washer disinfector should be carried out using satisfactory potable water, RO water or distilled water.
So, with so much attention on water quality throughout the practice it is not surprising that the water actually entering a patients’ mouth via dental unit water lines must also be closely monitored.
Guidance states that only distilled or RO water should be used in DUWLs, however the source of water for this purpose in some dental practices is most likely to be from the mains supply and as such the practice is reliant on the relevant utility company to ensure that the quality meets mentioned standards. This fact is recognised in HTM 01-05 guidance, which states, “For systems making use of potable water (that is, where the water supply is drawn from a mains water system), the nature of the building’s water-supply arrangements may be an important consideration.” However, in a field study carried out by Dentisan, evaluation of stored water for use in DUWL at four UK practices, monitored over a three month period, showed that only seven samples (20 per cent) had bacterial counts below the 200 cfu/ml limit, regardless of its source. These results indicate that in most cases (80 per cent of 35 samples) the water being introduced into a DUWL system did not meet the required standard for microbial contamination specified for output water. A unit fed with such water cannot be in compliance with guidelines as microbial contamination can only increase as water passes through the unit.
The failure of input water to meet quality standards must be addressed within the practice’s risk assessment and procedures established to ensure that input water is always of sufficient quality. In order to check water quality there are a number of options available to practices, and the use of Dip Slides is considered a reliable means of assessing relative levels of microbiological contamination in water. Plate counts can give more precise results but what is important with waterlines is to know the order of magnitude of contamination - does the water have 20cfu/ml, 200cfu/ml or 2000cfu/ml? The difference between 18 and 20cfu/ml or 1800 and 2000cfu/ml is irrelevant. Both 18 and 20cfu/ml would be interpreted as within limits, whereas 1800 and 2000cfu/ml would both be interpreted as over limit.
The need to continuously monitor contamination levels in dental unit water lines is to some extent determined by the nature of biofilm itself. In aqueous environments, biofilms form when individual planktonic (free floating) bacteria adhere to a surface, such as the wall of a tube. Biofilms form naturally when conditions are conducive and they are perfect in dental unit water lines where a series of conditions and properties such as a low flow rate, small bore tubing and an ambient temperature, combine to create the ideal environment for biofilm formation.
The only real way to ensure that the growth of biofilm is controlled, is to understand that eradication involving a one-time, purge of the system will not provide a long-term solution. It is still necessary to ensure that water lines are regularly monitored and maintained. As with all organic matter biofilm will grow wherever and whenever the prevailing conditions are right and because of this, dental practices need to ensure that they have systems in place to regularly monitor contamination levels. This can either be done using internal processes or by availing themselves of the services of an external testing laboratory, which will test water quality, produce a report and provide recommendations for treatment where appropriate.
Engaging with a third party in this manner can be a great advantage as it not only provides substantive evidence of testing and results for CQC and regulatory compliance, but also provides external validation for the processes being employed at individual practices.
When you don’t feel well, chances are the first thing someone does is take your temperature, thus providing a benchmark for whether your condition is improving or otherwise. For the same reasons the monitoring of decontamination in BOTH input and output water of DUWL systems is essential, as it gives a clear indication of where biofilm build-up is causing a contamination risk to patients and staff.