Dental Unit Water Systems Research Articles

Effects of Iodine in Microbial Control of Dental Treatment Water

To determine the effects of low levels of iodine constantly present in the dental unit water system on microbial control of dental treatment water and biofilm control. This study used a dental unit water system simulator with eight dental unit waterline systems built to scale and function, each controlled via computer. Each of the eight units was operated independently, four units supplied with self-contained water reservoirs and four units supplied with municipal water. Four units were precleaned to remove biofilm buildup. The study had a well-balanced design with equal representation (variables) of presence/absence of biofilms, selfcontained reservoirs for introduction of treatment water, source water directly connected to municipal water source and iodinated cartridges within the self-contained reservoirs and between municipal water and dental unit. Point-of-use iodinated resin cartridges (IRC) were retrofitted proximal to handpiece and air/ water syringe tip lines in four units, and iodinated resin water cartridges (IRSWC) were fitted to the other four units at the source water output. Heterotrophic plate counts were performed at baseline and twice weekly for a period of 6 weeks. One representative waterline sample was taken from each group at baseline and end-of-study to analyze changes in biofilm status using scanning electron microscopy. Waterlines not previously contaminated with biofilms did not show organization of biofilm matrix in units equipped with IRSWC. Constantly present low levels of iodine, demonstrated some disruption of biofilms in waterlines already contaminated with mature biofilms. All groups showed contamination levels < 500 cfu/ml (colony forming units per milliliter) consistent with the CDC and ADA guidelines. In this 6 weeks study, IRSWC equipped waterlines showed disruption of established biofilms, controlled formation of new biofilms in clean lines and rendered the dental treatment water < 500 cfu/ml. Point-of-use iodinated resin cartridges were also effective in controlling contamination in the dental treatment water. Dental unit water systems that are in use get contaminated with microbes and biofilms in weeks of being put into use. These biofilms contaminate the treatment water thereby putting patients and staff at risk of infection by predominantly gram-negative microbes. Biofilms in the water systems must be cleaned periodically with a strong decontaminant and the dental treatment source water needs to be modified with a low-grade antimicrobial that can preserve the water quality yet safe to humans. In this translational research study, we evaluate the effects of elemental iodine dissolved in water flowing through an iodine containing cartridge in controlling biofilm and dental treatment water contamination using a dental unit water system simulator, prior to clinical utilization.

P11.08 The effect of a mobile air purification unit on the air quality of a room contaminated with Aspergillus sp.

P11.08 The effect of a mobile air purification unit on the air quality of a room contaminated with Aspergillus sp.

P11.09 Water microfiltration at the point of use – a procedure to prevent infection/colonization with water borne pathogens in ICU patients?

P11.09 Water microfiltration at the point of use – a procedure to prevent infection/colonization with water borne pathogens in ICU patients?

Italian multicentre study on microbial environmental contamination in dental clinics: a pilot study

The dental practice is associated with a high risk of infections, both for patients and healthcare operators, and the environment may play an important role in the transmission of infectious diseases. A microbiological environmental investigation was carried out in six dental clinics as a pilot study for a larger multicentre study that will be performed by the Italian SItI (Society of Hygiene, Preventive Medicine and Public Health) working group "Hygiene in Dentistry". Microbial contamination of water, air and surfaces was assessed in each clinic during the five working days of the week, before and during treatments. Air and surfaces were also examined at the end of the daily activity. A wide variation was found in microbial environmental contamination, both within the participating clinics and relative to the different sampling times. Microbial water contamination in Dental Unit Water Systems (DUWS) reached values of up to 26 × 10 4 cfu/mL (colony forming units per millilitre). P. aeruginosa was found in 33% of the sampled DUWS and Legionella spp. in 50%. A significant decrease in the Total Viable Count (TVC) was recorded during the activity. Microbial air contamination showed the highest levels during dental treatments and tended to decrease at the end of the working activity (p < 0.05). Microbial buildup on surfaces increased significantly during the working hours. As these findings point out, research on microbial environmental contamination and the related risk factors in dental clinics should be expanded and should also be based on larger collections of data, in order to provide the essential knowledge aimed at targeted preventive interventions.

Assessment of the Efficacy of Intermittent Ozone Disinfection

An example of intermittent disinfection occurs in dental-unit water systems (DUWS), which are disinfected only for a specified time per each day. The efficacy of intermittent ozonation was evaluated using a laboratory-scale, membrane-based ozone disinfection system (MBODS), which delivers bubbleless dissolved ozone to the DUWS. A new tool - the weighted Ct value, or Cw, - was applied to interpret heterotrophic plate counts (HPC) data. To achieve the American Dental Association's (ADA's) criterion (<200 CFU/mL), the required ozone dosage was Cw > 0.07 mg–O3/L. However, even the highest ozone dosage (Cw > 0.130 mg/L) allowed biofilm HPC to persist at over 104 CFU/cm2. Although a higher Cw killed planktonic and biofilm bacteria more thoroughly, it also generated more biodegradable dissolved organic carbon (BDOC). Thus, this research illustrates the inherent trade-off of intermittent ozonation: a higher Cw kills more bacteria during the ozonation period, but creates more BDOC that fosters biofilm regrowth when ozonation is off.

Control of microbial contamination in dental unit water systems using tetra-sodium EDTA

To examine the efficacy of tetra-sodium EDTA in controlling microbial contamination of dental unit water systems (DUWS). Ten dental units were treated once a week with either 4% or 8% tetra-sodium EDTA for four or two consecutive weeks, respectively. Before treatment, 43% and 60% of the water samples from the air/water triple syringe and high-speed hand-pieces, respectively, exceeded the American Dental Association (ADA) guidelines of 200 CFU ml(-1) water during a 6-week baseline period. After each weekend treatment, the levels of microbial contamination in all DUWS fell significantly (P < 0.001) to below the ADA guideline. By the end of the week, microbial counts in the outflowing water had returned to baseline levels indicating a transient effect of single doses of tetra-sodium EDTA, and the need for multiple applications. The biofilms were virtually eliminated after a single weekend treatment. Tetra-sodium EDTA is effective in controlling microbial contamination in DUWS. Inexpensive, effective and safe products for reducing the microbial load of water from DUWS are needed to meet ADA and other national guidelines. Tetra-sodium EDTA can significantly reduce microbial biofilms and bacterial counts in outflowing water, and is compatible for use in DUWS.

Biofilm problems in dental unit water systems and its practical control

Dental chair units (DCUs) contain integrated systems that provide the instruments and services for a wide range of dental procedures. DCUs use water to cool and irrigate DCU-supplied instruments and tooth surfaces during dental treatment. Water is supplied to these instruments by a network of interconnected narrow-bore (2-3 mm) plastic tubes called dental unit waterlines (DUWLs). Many studies over the last 40 years demonstrated that DUWL output water is often contaminated with high densities of micro-organisms, predominantly Gram-negative aerobic heterotropic environmental bacteria, including Legionella and Pseudomonas species. Untreated DUWLs host biofilms that permit micro-organisms to multiply and disperse through the water network and which are aerosolized by DCU instrument use, thus exposing patients and staff to these micro-organisms, to fragments of biofilm and bacterial endotoxins. This review concentrates on how practical developments and innovations in specific areas can contribute to effective DUWL biofilm control. These include the use of effective DUWL treatment agents, improvements to DCU supply water quality, DCU design changes, development of automated DUWL treatment procedures that are effective at controlling biofilm in the long-term and require minimal human intervention, are safe for patients and staff, and which do not cause deterioration of DCU components following prolonged use.

Effects of Shock Treatment for Water Delivered by Dental Unit Water Systems : Trial in the Tsurumi University Dental Hospital

Effects of Shock Treatment for Water Delivered by Dental Unit Water Systems : Trial in the Tsurumi University Dental Hospital

Comparison of the microbial load of incoming and distal outlet waters from dental unit water systems in Istanbul

This is a cross-sectional study of the incoming and distal outlet water quality from 41 dental units in Istanbul, carried out to compare the total microbial loads using traditional culture method versus epifluorescence microscopy. The possible presence of Legionella pneumophila using traditional culture method was also analyzed. One hundred and twenty three samples were taken from the high-speed handpiece lines, air-water syringe lines and source (incoming) water supplies from 41 dental units. The samples were assayed for live/dead bacteria, heterotrophic bacterial counts and presence of L. pneumophila bacteria. Thirty nine out of 41 dental units (91%) were not able to meet the standard limit of 200 CFU/ml in dental unit waters. The live bacterial counts were 1-1.5 orders of magnitude higher than aerobic mesophilic heterotrophic bacteria. L. pneumophila (serogroup 2-14) was isolated from five out of 41 units. Some dental units were using commercially bottled (19 l) drinking water as a source. The source water of eight dental unit was heavily contaminated which were fed up by commercially bottled drinking water.

Análise bacteriológica da água de equipos odontológicos

Although, in recent years, great efforts have been made to inform and make health professionals aware of the importance of sterilization, disinfection and antisepsis, little considerations have been shown in relation to the quality of the water of dental unit systems. In the present work 72 samples of water from 68 dental equipments and 4 faucets were submitted to bacteriological analysis, with the objective of detecting heterothrophic bacteria and coliform group. The samples collected from the faucets were compatible with the water potability patterns. In contrast, 63 (92.7%) of the 68 samples obtained from the dental unit water systems were considered contaminated and only 5 (7.3%) were in agreement with the potability patterns. It was observed that 42 water samples (61.8%) were heavily contaminated, 14 (20.6%) presented moderate index of contamination and 7 (10.3%) were slightly contaminated. The results suggest the need of decontamination of water reservoirs and hoses of these equipments

Microbiological evaluation and antibiotic susceptibility of dental unit water systems in general dental practice

The microbial quality of water in a dental unit water systems (DUWS) is of considerable importance because patients and dental staff are regularly exposed to water and aerosol generated from the dental units. The objective of this study was to evaluate the 20 DUWS in general dental practices and to determine the antibiotic susceptibility of the colonizing bacteria. Three water and one biofilm samples from each DUWS were investigated for total viable count (TVC), oral streptococci, Pseudomonas spp., Enterobacteria, Candida albicans and Legionella pneumophila. A total of 44 morphologically different colonies were obtained from water samples and 20 types of colonies (45.5%) could be identified using API test strips. The mean TVC values were 4.36 log CFU ml(-1) for source waters, 4.95 log CFU ml(-1) for 3-in-1 syringe samples, 4.91 log CFU ml(-1) for air rotor samples and 3.66 log CFU cm(-2) for biofilm samples. Susceptibilities of the isolates were tested against piperacillin, ampicillin, ceftazidime, meropenem, gentamicin, tetracycline, ofloxacin and chloramphenicol by using microdilution method according to NCCLS. The meropenem and ofloxacin have shown the broadest spectrum against to the tested isolates. The study emphasizes the need for effective mechanisms to reduce the microbial contamination in DUWS, and highlights the risk for cross-infection in general dental practice.

Legionella in the dental office

This study aimed to assess the microbiology of dental unit water and municipal water in terms of Legionella species and total bacteria levels. The presence of Legionella species was investigated using the culture method, direct fluorescent antibody and polymerase chain reaction techniques in collected dental unit water and municipal water samples from 71 dental offices in Ankara, Turkey. In addition, total bacterial counts were assessed using the culture method. In 27% of the dental unit water samples and in 13% of municipal water samples, the number of colony-forming units (cfu ml(-1)) significantly exceeded acceptable values for high-risk group patients. No Legionella spp. was found in the dental unit water samples. Legionella SG3 was found in only one municipal water sample. The dental unit water systems examined in this study did not include Legionella spp., but other bacteria at high numbers were determined. This is a potential threat, especially for elderly people, the medically compromised patients receiving regular dental treatment and the dental clinic staff.

Attitudes of general dental practitioners in Europe to the microbial risk associated with dental unit water systems

Dental Unit Water Systems (DUWS) are used in dental practices to provide water for cooling of dental equipment and irrigation of the oral cavity. However, they have been demonstrated to be contaminated with micro-organisms. There are currently no European Union (EU) Commission guidelines for the microbial quality of water discharged by DUWS. This study was part of an EU research programme to investigate the microbial contamination of DUWS in general dental practice (GDP) in the UK, Denmark, Germany, The Netherlands, Ireland, Greece and Spain. To undertake a questionnaire survey on the type of DUWS in use and determine the attitude of GDPs to the risk of microbial infection from DUWS. The questionnaire was written and translated into the language of each country before being posted to each participating dentist. Dentists were asked to complete the questionnaire survey and return it by post. The major findings were that the majority of dentists did not clean, disinfect or determine the microbial load of their DUWS, and that dentists would welcome regular monitoring and advice on maintaining their DUWS; the introduction of guidelines; and recommendations on controlling the microbial load of DUWS.

Microbial risk assessment of dental unit water systems in general dental practice in Greece

Water was sampled from source water, the 3-in-1 syringe and the air rotor water line of dental unit water systems (DUWS) in general dental practice in Attica, Greece. A section of the water line supplying the 3-in-1 syringe was cut for biofilm analysis. High total viable counts, Mycobacterium spp. and Pseudomonas aeruginosa were detected in the samples. Back siphonage was evidenced by the presence of blood and the recovery of oral anaerobes from the samples. Legionella pneumophila was recovered from 16.1% of biofilm samples. All tested disinfectants reduced the total viable counts of the DUWS to < 100 CFU/mL.

Microbiological evaluation of dental unit water systems in general dental practice in Europe

Microbiological evaluation of dental unit water systems in general dental practice in Europe

Microbiological evaluation of dental unit water systems in general dental practice in Europe.

A range of opportunistic pathogens have been associated with dental unit water systems (DUWS), particularly in the biofilms that can line the tubing. This study therefore aimed to assess the microbiology of DUWS and biofilms in general dental practices across seven European countries, including the United Kingdom (UK), Ireland (IRL), Greece (GR), Spain (ES), Germany (D), Denmark (DK) and the Netherlands (NL). Water supplied by 51% of 237 dental unit water lines exceeded current American Dental Association recommendations of < or = 200 colony-forming units (CFU) ml(-1). Microbiological loading of the source waters was between 0 (Denmark, the Netherlands and Spain) and 4.67 (IRL) log CFU ml(-1); water line samples from the DUWS ranged from 1.52 (ES) to 2.79 (GR) log CFU ml(-1); and biofilm counts ranged from 1.49 (GR) to 3.22 (DK) log CFU.cm(-2). Opportunistic pathogens such as legionellae (DK and ES), including Legionella pneumophila SG1 (DK and GR), and Mycobacterium spp. (DK, NL, GR, D and ES) were recovered occasionally. Presumptive oral streptococci (ES and NL), oral anaerobes (GR), Candida spp. (UK, NL and ES) and blood (GR and IRL) were detected at relatively low frequencies, but their presence indicated a failure of the 3-in-1 antiretraction valve, leading to back siphonage of oral fluids into the water and biofilm phase. These findings confirm that a substantial proportion of DUWS have high levels of microbial contamination, irrespective of country, type of equipment and source water. The study emphasizes the need for effective mechanisms to reduce the microbial burden within DUWS, and highlights the risk of occupational exposure and cross-infection in general dental practice.

A review of biofilms and their role in microbial contamination of dental unit water systems (DUWS)

Biofilms are heterogeneous functional consortia of microbial cells that grow on surfaces. This review discusses how biofilms form and why dental unit water systems (DUWS) are susceptible to biofilms composed of environmental (e.g. Moraxella spp. and Flavobacterium spp.) and opportunistic pathogens (e.g. Pseudomonas aeruginosa, Legionella pneumophila and Mycobacterium spp.). DUWS have narrow-bore tubing, slow flow and long stagnant periods that encourage biofilm growth. To control the microbial loading of DUWS, surgeries have used filtration, ultraviolet light and flushing. Dental practitioners are now being encouraged to retrofit independent water supplies that enable the practitioner to apply control strategies using chemicals such as sodium hypochlorite, chlorine dioxide, peroxides, peracetic acid and citric acid. Owing to the recognition of the public health significance of microbially contaminated DUWS, a vast range of chemical and non-chemical products have been developed in the last 3 years. With an increasing number of immuno-compromised dental patients presenting at dental surgeries, practitioners are now being given the mechanisms with which to control biofilms and maintain microbial numbers below the European Union drinking water guidelines and American Dental Association DUWS standard of 100 and 200CFUml−1, respectively.

Microbiological contamination of dental unit water systems in general practices from Barcelona (Spain)

Dental Unit Water Systems (DUWS) can be a source of contamination to dentists and patients, especially those who are immunocompromised. Such organisms may originate from incoming water supplies and from oral cavities. The most common cause of dental unit water contamination is believed to be the formation and subsequent sloughing off of microbial biofilms from tubing within DUWS. There are no evidence-based guidelines currently available to dentists for the control of DUWS contamination in Europe. The aim of this study was to investigate the microbial load of water from DUWS, especially the presence of microbial pathogens which can be a source of cross-contamination between patients. Water and tube samples were obtained from 40 dental surgeries in Barcelona. The samples were taken from turbine and from air/water syringe. Twelve of these DUWS were fed with hard water from mains (with chlorine) and 28 dental units with bottle or tank deionized water. Microbial load was ranged from 0 to 3.6 × 103 colony-forming units/mL. Legionella sp., Mycobacterium sp., Pseudomonas aeruginosa and Candida sp. were found in 4, 8, 6, and 2 different surgeries, respectively. Inclusive oral streptococci were found in 2 dental units indicating that there is a back siphonage in the systems analysed.

Abstracts of a joint meeting of the Association of Clinical Oral Microbiologists and the Biofilm Club held at the Eastman Dental Institute, University College London on 2 March 2004

Principles of antimicrobial biomaterials: why they do not (usually) workCharacterization of bacterial adhesion onto surfaces of stainless steel by micromanipulationYersinia spp./C. elegans infection model: biofilms on a biotic surfacePeriodontal pathogens in dental unit waterlinesBiofilms as reservoirs of antibiotic resistanceSystemic antimicrobials and periodontitis – a classic biofilm diseasePrion disease in the dental settingReviewing the role of biofilms in infection controlInfection control in dental technology laboratoriesReview of the treatment aspects of dental unit water systems

Total viable counts, ATP, and endotoxin levels as potential markers of microbial contamination of dental unit water systems.

To determine if either ATP or endotoxin concentrations in water supplied by dental unit water systems (DUWS) correlated with total viable counts (TVC), and therefore could be used as a rapid, chairside measure of levels of microbial contamination. A prospective trial. Fifty-seven water samples were taken from the 'triple spray', air rotor and source water supplies from 25 dental units in eight practices. The samples were assayed for endotoxin concentration, total ATP and TVC. A pilot study was performed to assess the relationship between TVC and total cell counts, as determined by flow cytometry. ATP concentrations ranged from 22 to 958 relative light units (RLU) and free endotoxin ranged from 25 to 600 EU ml(-1). TVC varied from not detected to 2.16 x 10(4) CFU ml(-1). The ATP method proved to be a simple and rapid method that could be used at the chairside. However, there was no correlation between ATP or endotoxin concentrations and TVC in DUWS. TVC generally underestimated the total cell count by 50 to 500 fold. Half of the water samples from DUWS exceeded recommended levels of TVC. However, ATP and endotoxin concentrations in DUWS water samples did not correlate with these TVC data and therefore could not be recommended as an alternative assay to TVC for measuring bacterial contamination or for monitoring water treatment efficacy.