CORDIS provides links to public deliverables and publications of HORIZON projects.
Links to deliverables and publications from FP7 projects, as well as links to some specific result types such as dataset and software, are dynamically retrieved from OpenAIRE .
Deliverables
Different manufacturers may recommend specific products to be used in their equipment, e.g. because of materials compatibility issues. Therefore, practitioners should consult with the manufacturer of their DUWS prior to introducing any chemical agent, as this may otherwise invalidate their warranty. Even chemical treatments are not a panacea as there are reported problems such as resistance to antimicrobials.
In addition, DUWS have brass-coupling connectors that are corroded by too harsh a chemical treatment, leading to leaks and failure of the DUWS. Where chemicals are used they could come into contact with the oral cavity and teeth. This has raised some concerns as some chemicals have been found to decrease the adhesion of resins to both enamel and dentin; hence restoration fillings may fail prematurely. Also, in addition to this, although some decontamination processes have been shown to decrease the coverage and TVC of biofilm tubing significantly, they have also demonstrated a significant increase in the number of planktonic micro-organisms subsequently being delivered in the water to the patient. The risk issue of exposure of the chemical product to the patient and health care workers also has to be considered when using disinfectant products in DUWS.
In this current trial, 10 different disinfectant products were used in 7 different countries. A number of criteria were used to judge the products including the ability to reduce the water phase and biofilm TVC to < 200 cfu.ml-1, ability to remove the biofilm, ease of use and compatibility. In addition to those, which were chosen following the laboratory trial, a few others were also tested. Alpron and the hydrogen peroxide products were identified as the most appropriate products for microbial control in DUWS. These included Sanosil, HWP Blue, Oxygenal and Dentasept. Although Alpron had the drawback for the participants in that it required a three-stage application even though utensils were supplied and in Spain resulted in foaming and a browning of the water. In order of preference, BioBLUE was rated as the next best product although it does not have a CE mark.
Ster4spray was limited and it did not always reduce the TVC to less than 100 cfu.ml-1 and also resulted in clogging and blocking of the DUWS. Sterilex Ultra was identified as the worst product used due to the materials compatibility issue.
Dental Unit Water Systems (DUWS) are used in dental practices to provide water to irrigate the oral cavity, and have been demonstrated to be heavily contaminated with micro-organisms, particularly in dental hospitals. There is currently no EU Commission guideline applied to DUWS. The aim of this EU programme was to investigate the microbial contamination of DUWS in general dental practice (GDP) in the UK, Denmark, Germany, The Netherlands, Ireland, Greece and Spain by:
- Carrying out a questionnaire survey on DUWS type in use, their water supply and GDP attitude to the risk of microbial infection from DUWS,
- Assessing the total microbiological loading and the presence of particular pathogens in DUWS water as well as the presence of biofilms using TVC and microscopy,
- Evaluating the efficacy of a variety of products based on different classes of active compound using a laboratory model to generate reproducible biofilm on DUWS tubing and,
- Applying disinfectants identified from the laboratory model to DUWS in general dental practice for the control of microbial contamination in GDP.
The major findings were that:
The majority of dentists did not clean, disinfect or analyse the microbial load of their DUWS. Dentists would welcome regular monitoring and advice on cleaning their DUWS. The microbial load of DUWS in the different countries ranged from 0 to 4.4 x 104 cfu.ml-1.
Water supplied by 44% of dental units in this microbiological survey of GDP DUWS failed current European Union potable water guidelines (100 cfu ml-1) and 51% failed American Dental Association (ADA) recommendations (200 cfu.ml-1).
Biofilms were identified as a source of contamination; therefore effective products should be able to reduce the biofilm load within DUWS.
Irrespective of overall contamination, pathogens such Pseudomonas spp., enterobacteria, Legionella spp. Mycobacterium spp. and Candida sp. could occasionally be detected, as could presumptive oral bacteria, indicating possible failure of anti-retraction valves and potential for cross-infection incidents.
The laboratory model was designed and established to investigate products for reducing the microbial load and presence of biofilm on DUWS tubing using a range of commercially available and novel products. Following comparative trials, the products Sterilex Ultra, Alpron, Sanosil, Oxygenal and BioBLUE were selected to be administered to the DUWS in GDP. The following products were identified as being effective where used in GDP¡¦s:
Hydrogen-peroxide based products (including Sanosil, HWP Blue, Oxygenal and Dentasept).
Alpron
BioBLUE was rated as the next best product
Ster4spray was limited in efficacy
Sterilex Ultra was problematic resulting in clogged and blocked DUWS.
The partners in the programme would recommend that:
The application of products should be carried out in combination with education and training of the staff involved as well as an appropriate monitoring regime as part of the GDP's cross-infection control strategy.
The EU adopts the same standard as the ADA in that the water in DUWS should contain < 200 cfu.ml-1. Where administered then effective products such as Alpron and the hydrogen peroxide based products should be used.
Dissemination:
This is in the form of responses to invitations to speak at both small local meetings that are part of the ongoing education for dentists and their teams and at large national or international meetings. Invitations have been accepted to speak at the British Dental Association's (BDA) annual conference, which has a large attendance including overseas delegates, the British Orthodontic Society's annual conference and a large international infection control symposium to be held in Scotland later this year. It has been proposed to make a TV programme on the subject, aimed primarily at dentists, to be broadcast on satellite TV later this year. The results are also to be featured on a CD ROM currently being produced and to be distributed to all UK dentists by the Department of Health. Similar approaches are being taken in each of the partner countries.
Proactive: Encouraging other organisations to include the subject in their educational programmes for dentists both by verbal or written presentations. The findings have also been fed into the BDA Health and Science Committee, which will lead to national guidelines to be promulgated to all UK dentists. In addition, submission of abstracts and presentations for consideration by national and international dental research groups affiliated to IADR based on the data generated in this study.
Water supplied by 51% of dental units in this general practice survey failed ADA recommendations on microbial load (<200 cfu.ml-1) (Anonymous 2002). Although the absolute microbial numbers reported in this study are lower than those reported elsewhere (Depaola et al. 2002, Pederson et al. 2002, Tuttlebee et al. 2002, Walker et al. 2002) it is still unsatisfactory that ~50% of units tested did not meet the above recommendations.
A number of studies have indicated that dentists have higher rates of respiratory infections than the general public and that in some cases 25% of dental units have been reported positive for L. pneumophila (Atlas et al. 1995, Challacombe et al. 1995). In this study the actual numbers and prevalence of Legionella spp. were low. Pathogens such as Legionella spp. were recovered in 5% of cases with L. pneumophila isolated from 0.8% of samples. A pilot study in The Netherlands suggested that culture approaches might underreport the presence of Legionella spp., since molecular tests resulted in a detection rate of 55 %. Similarly, other water-associated pathogens were only detected occasionally, e.g. P. aeruginosa and coliforms were reported in 7% and 1% of samples, respectively. Mycobacteria were detected in 74% of samples. These isolates were not identified to species level and although their pathogenic potential is not known several non-Mycobacterium tuberculosis and non-Mycobacterium avium species are associated with a variety of infections (Goslee et al. 1976). Candida spp (1.6%) and presumptive oral streptococci (2%) were detected indicating a failure of the 3-in-1 antiretraction valve and potential back siphonage of oral fluids. This suggests a potential risk for cross infection incidents between patients. With the ever increasing presentation of HIV positive patients and Hepatitis B carriers, due diligence must be undertaken to minimise the risk for cross infection resulting from the use of DUWS, particularly to immuno-compromised patients (Porter 2002). There were marked differences among countries in the level of contamination of DUWs. However, irrespective of the total microbial load, the water and the distal outlet could still contain opportunistic pathogens. Therefore cross infection is still a genuine risk and practice managers need to adopt strategies to see that the water delivered from all units meets acceptable standards. There are now an increasing number of commercial products on the market that practice managers can use to reduce the microbial burden of their DUWS and reduce the risk of occupational exposure and cross infection (Pederson et al. 2002).
Current studies are evaluating a broad range of products suitable for use in DUWs that attack bio-film. A number of products were subjected to an independent head-to-head comparison in a laboratory model in this study.
This study involved the largest survey of GDP's undertaken in the EU. This involved recruiting 436 GDP's in the UK, Denmark, Germany, The Netherlands, Greece, Spain and Ireland. Of the GDP's recruited 258 (59%) completed and returned their questionnaires. The majority of the DUWS (66%) were more than five years old and were fed by mains water. This may have treatment implications as older systems may have established biofilm that are even more difficult to treat. In the UK all the DUWS were fed by independent water reservoirs reflecting the requirement of the local water authority that potential back-siphonage incidents be reduced by removing DUWS from the mains water.
Countries such as The Netherlands, Greece and Denmark have >98% of DUWS supplied by mains water. In this context, the application of disinfectants is more complex. Independent purge dispensers (Mycrillium, Toronto, Canada) were retrofitted to the mains supply line in order for disinfectants to be added to the DUWS. Spain and Ireland had 18%, and 27%, respectively of systems supplied by water from tanks. The mains water supply chemistry varied depending on whether soft (<50ppm CaCO3) (34%) or hard water (31%) was used (200ppm CaCO3). A supply of hard water may result in a calcium layer being deposited on the inner pipelines and valves, providing an even greater ratio of surface area to volume for biofilm growth and possibly contributing to early valve failure. Only 24% of all the systems surveyed used bottle supply to the DUWS. The use of tap water or even sterile water in DUWS would be predicted to decrease the likelihood of failure to meet the water guidelines. Unfortunately, with time, even DUWS supplied by sterile water (either deionised or distilled) will become colonised to the same extent as those supplied by tap water. This does create a difficulty for some practitioners, who because they are using sterile water, believe they have a sterile dental line. Systems can be designed to employ single-use disposable or autoclavable tubing to by-pass the DUWS and provide sterile irrigating solution directly to the hand-piece (assuming that the hand-piece has also been disinfected). 97% of the surgeries did not have microbiological analysis carried out on their water indicating that they would not know the microbial load of their DUWS. From the survey it was found that 48% of the units were flushed between patients.
The British Dental Association (BDA), American Dental Association (ADA) and Centre for Communicable Disease Control (CDC) recommend flushing the water line for several minutes prior to the first patient and for 20-30 seconds between patients. Flushing between patients has been shown to decrease the number of bacteria in the water phase (Scheid et al. 1990). However, this reduction will be transient as the micro-organisms will logarithmically multiply back to high numbers relatively quickly, as has been shown with L. pneumophila in water systems. In addition to this it has been demonstrated that flushing has little or no effect on the biofilm as the laminar flow will barely result in sloughing. 75% of surgeries indicated that they did not clean nor disinfect their DUWS. This varied within countries (e.g. 66, 68 and 76% of surgeries in the Netherlands, Ireland and Greece, respectively, did not clean or disinfect). Whilst 66% of the dentists had received guidance on cleaning/disinfection of the water lines, presumably from the supplier of the DUWS, >98% were not aware of national/international guidelines for microbial contamination of DUWS. This indicates that the national dental associations should be more proactive in dissemination of information on this area of cross infection control.
Approximately half of all dentists do not spend any money (51%) or time (45%) treating their DUWS. Across the EU this would represent a large number of units that receive no treatment. Although 65% of dentists expressed a concern about the quality of water flowing through the dental unit, half of them believed that the quality of water delivered by their dental unit was the same as the water that was put into it. This perhaps indicates that more education and information about microbial growth and the risks from the growth of opportunistic pathogens in the DUWS is required to be disseminated to dentists across the EU. Similarly, the majority of dentists (65%) did not perceive the water in the DUWS as a hazard to them or their staff. This was surprising since other studies have demonstrated that dental personnel have been shown to have higher antibody titres to Legionella than other non-dental control populations, again highlighting the need for a wider dissemination of information.
The dentists are concerned about the quality of water flowing through their dental unit and would welcome regular microbiological testing of the water and clear advice on cleaning/disinfection of the water supply in their dental unit.
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