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Background: Microbiological contamination of water in dental unit waterlines (DUWL) creates a risk of cross-infections, and is a source of biological risk factors in the work environment of a dentist. The aim of the study was to evaluate dentists' knowledge on DUWL microbiological contamination and the scope of activities/procedures they undertake to monitor it., Materials and Method: The questionnaire survey was conducted in 2010 among 107 Polish dentists using dental units in everyday clinical practice., Results: It has been found that in their daily practice, dentists do not follow procedures leading to reduction or elimination of microbiological contamination of dental unit reservoir water. They are not aware of microbiological contamination of DUWL that supply working handpieces with water. They are unaware of the principles of dealing with dental water and water supply systems or the health risk posed by microbiological contamination of unit water for a dental team and patients., Conclusions: It is necessary to provide dentists with information on microbiological contamination of water in dental units, on the correct procedures of handling water and waterlines that supply working handpieces with water.

The specific structure of dental units favours the presence of biofilm and microbial contamination of the dental unit waterlines (DUWL) water. The ability of bacteria to colonize surfaces and to form biofilm in water supply tubes, including DUWL, is a common phenomenon, which has been well documented, just as with difficulties in biofilm removal and prevention of its regrowth. Microorganisms from contaminated DUWL are transmitted with aerosol and splatter, generated by working unit handpieces. On the basis of the detailed literature review, the state-of-the art knowledge of the microflora of dental unit waterlines is presented. Most of the microorganisms isolated from DUWL are of low pathogenicity. Nevertheless, the public health significance of many of the microorganisms found in DUWL is unknown. According to current knowledge, it is not the mere presence of bacteria that is important in DUWL contamination monitoring, but their number, the presence of potential pathogens, and patients' oral cavity microflora. Numerous studies emphasize the need for effective mechanisms to reduce the microbial contamination in DUWL and highlight the risk for cross-infection in general practice, especially in view of the ever-increasing number of immunocompromised persons who present at outpatient dental clinics.

The aim of this study was bacteriological assessment of water in dental unit reservoirs--concentration and composition of the aerobe and facultative anaerobe bacterial microflora. Reservoir water samples were taken from 25 units. Bacterial flora were determined with the plate culture method. Bacteria were identified with biochemical microtests: API 20E, API 20NE (bioMérieux, France) and GP2 MicroPlateTM (BIOLOG, USA). The concentration of total bacteria isolated from one site was 201,039 cfu/ml, on average; the minimum was 22,300 cfu/ml, and the maximum - 583,000 cfu/ml. The following bacteria were identified: Gram-negative bacteria--Brevundimonas vesicularis, Moraxella lacunata, Moraxella spp., Ralstonia pickettii, Sphingomonas paucimobilis, Stenotrophomonas maltophilia; Gram-positive cocci--Micrococcus luteus, Micrococcus lylae, Staphylococcus cohnii, Staphylococcus hominis ss novobiosepticus, Staphylococcus spp., Streptococcus spp.; actinomycetes--Streptomyces albus. The prevailing bacteria were: Ralstonia pickettii (96.46%), found in all the units. Sphingomonas paucimobilis (1.32%) and Brevundimonas vesicularis (1.07%) were the next most frequently occurring bacteria. Bacteria concentration in dental unit reservoirs reached excessive values, and the bacterial flora were composed of the bacteria characteristic for water supply systems, opportunistic pathogens, and bacteria of the oral cavity flora. Continuous microbiological monitoring of the DUWL water, including application of a disinfecting procedure, is necessary.

The concentration and composition of fungal flora in dental unit waterlines (DUWL) were evaluated. For this purpose, water samples from unit reservoirs and high-speed handpieces, and biofilm samples from the waterline walls from units were collected. Subsequently, analogous samples from DUWL were taken before and after disinfection using agent containing hydrogen peroxide. In the examined samples, the yeast-like fungi Candida albicans and Candida curvata were found. The following species of mould were also identified: Aspergillus amstelodami, Aspergillus fumigatus, Aspergillus glaucus group, Aspergillus (=Eurotium herbariorum) repens, Citromyces spp., Geotrichum candidum, Penicillium (glabrum) frequentans, Penicillium pusillum, Penicillium turolense and Sclerotium sclerotiorum (Sclerotinia sclerotiorum). Before disinfection, Candida curvata and Candida albicans constituted the greatest proportion of the total fungi in the reservoirs water; in the water of handpieces--Candida albicans and Aspergillus glaucus group; and in the biofilm samples--Aspergillus glaucus group and Candida albicans. After disinfection, in all 3 kinds of samples, Candida albicans prevailed, constituting from 31.2-85.7 % of the total fungi. The application of agent containing hydrogen peroxide caused a significant decrease both in the number of total fungi and individual fungal species, which confirms the product effectiveness in fungal decontamination of DUWL.

The aim of this study was bacteriological assessment of the dental unit waterlines (DUWL) biofilm - concentration and composition of the aerobe and facultative anaerobe bacterial microflora, and evaluation of the influence of a disinfecting product, Oxygenal 6, on the biofilm composition. Tubing fragments were taken from 25 units twice, before and after disinfection, and bacterial suspension of the biofilm was obtained from the samples. The bacterial flora was determined with the plate culture method. Bacteria were identified with biochemical microtests: API 20E, API 20NE (bioMerieux, France) and GP2 MicroPlate(TM) (BIOLOG, USA). Before disinfection, the following bacteria were identified: Gram-negative bacteria - Ralstonia pickettii, Pseudomonas vesicularis, Sphingomonas paucimobilis, Xanthomonas maltophilia; Gram-positive cocci - Micrococcus luteus, Micrococcus lylae, Staphylococcus cohnii, Staphylococcus lentus, Staphylococcus spp., Streptococcus spp.; Actinomycetes - Streptomyces albus. The prevailing bacteria were: Ralstonia pickettii (78.62%), found in all the units, and Sphingomonas paucimobilis (20.45%). After DUWL disinfection, Sphingomonas paucimobilis (88.79%) dominated in the biofilm, Staphylococcus spp. - 5.61% and Pseudomonas spp. - 3.74% were next most frequently occurring bacteria, and in more than a half of the biofilm samples 100% reduction of the bacterial microflora occurred. This study confirms effectiveness of Oxygenal 6 in bacterial decontamination of the DUWL biofilm.

The quality of dental unit water is of great importance since patients and dental staff are regularly exposed to water from aerosols generated during work. The main purpose of this investigation was mycological evaluation of dental unit waterlines (DUWL). The author determined the number and species of fungi present in the water from a unit reservoir which is the source of water for a dental unit, in the water flowing from a high-speed handpiece of a unit, and in the swab sample collected from the wall of a waterline connecting a unit reservoir and dental handpieces. The following mould fungi were identified: Aspergillus amstelodami, Aspergillus fumigatus, Aspergillus spp. from Aspergillus glaucus group, Aspergillus repens, Citromyces spp., Geotrichum candidum, Penicillium aspergilliforme, Penicillium pusillum, Penicillium turolense, Sclerotium sclerotiorum; yeast-like fungi: Candida albicans, Candida curvata and other yeasts. Some of them, in certain circumstances, especially in people with immunological disorders, may be a cause of opportunistic infections. Thus, it is necessary that the DUWL should be submitted to a decontamination protocol and to routine microbial monitoring to guarantee an appropriate quality of water used in dental treatment.

Using the transmission electron microscope, the ultrastructural examination was conducted to detect the presence of bacterial biofilm on the inner surfaces of the tubing in dental unit waterlines (DUWL). Samples for examination were taken from the tubes providing water to high-speed and slow-speed handpieces, and to an air-water syringe before application of a disinfection procedure. The microscopic analysis made it possible to find the biofilm in all the tubes in the dental unit which were not pre-disinfected. In these samples, no significant differences were found between high-speed, slow-speed and air-water lines.

Microbial quality of water in a dental unit is of considerable importance since patients and dental staff are regularly exposed to water and aerosol generated by the unit. Water delivered to a dental unit by the so-called independent water system is the water coming from a reservoir which, at the same time, is an initial part of dental unit waterlines (DUWL). Thus, microbiological quality of this water is extremely important for the quality of water flowing from dental handpieces. The aim of the study was to assess microbiologically the water contained in dental unit reservoirs. Water samples were collected aseptically from the water reservoirs of 19 dental units. Results concerning microbial contamination: potable water quality indices, and detection and isolation of Legionella species bacteria, were presented. Over a half of the samples did not comply with the norms for potable water. In 63.1% of the cases, the number of colony forming units (cfu/ml) and of coliform organisms significantly exceeded acceptable values. Enterococcus was not detected in the samples of examined water. Similarly, no Legionella were found in the samples of dental unit reservoirs water. Reservoirs as water supplies and initial segment of DUWL should be subject to protocol to eliminate microbial contamination and routine monitoring to guarantee an appropriate quality of water used in dental treatment.