The water used in dental unit waterlines (DUWLs) acts as a coolant for the high-speed equipment and as an irrigant during dental treatments. There are kind of water tanks. DUWLs provide a favorable environment for microbial biofilm and multiplation primarily due to the high surface in the tubing and the character of fluid dynamics in narrow, smooth-walled waterlines. Biofilms can harbour opportunist pathogens such as Legionella sp., Pseudomonas sp. Several studies have shown that DUWLs have high levels of microbial contamination. Presence of high level of microbial contamination is an important problem for dentists and dental patients who are immunocompromised. We collected water samples from DUWLs of 20 private dental offices. We have determined that only 2 (3.4%) out of 59 dental unit water samples were found to meet the standard (<200 CFU.ml(-1)) for DUWLs water quality by American Dental Association (ADA). Of the 59 water samples examined, 14 (24%) were positive for Pseudomonas sp. and 18 (30.5%) were positive for fungi. The most common 14 bacterial strains and seven fungi were isolated. Of bacterial strains, 57.1% were identified: Majority of the bacterial species isolated from our samples was identified as Pseudomonas fluorescens, Pasteurella haemolytica, Photobacterium damsela, Ochrobacter anthropi, Moraxella sp., Aspergillus flavus, Penicillium expansum. Legionella sp. were not detected in all water samples.

Some bacteria have a higher tendency to produce biofilm than others. Especially, Pseudomonas and Aeromonas strains are acknowledged to be pioneer colonizers and are predominant in biofilm formation. We examined biofilm formation and first attachment maintance of biofilms of Pseudomonas spp., Pseudomonas aeruginosa, Aeromonas spp, sulphate reducing bacteria and filamentous fungi. A simulated recirculating cooling-water system was used. Heterotrophic bacteria counts on galvanized steel and glass surfaces rose during the tidy period of 720 hours. In addition, we determined that although Pseudomonas spp., Pseudomonas aeruginosa and Aeromonas spp. were the pioneer colonizers, they surprisingly could not be determined in the biofilms on both types of surface after 456 hours. Sulphate reducing bacteria were observed in biofilms on both surfaces from the outset of the experiments. Filamentous fungi were seen on the galvanized steel and glass surfaces after 0.5 h.

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.

Although bacterial contamination is widely researched in dental unit water systems, we have been unable to find any published reports to date about the presence and distribution of sulphate-reducing bacteria (SRB) in dental unit waterlines (DUWLs). The aim of this study was to evaluate microbial contamination and to determine the presence and distribution of SRB in DUWLs. One hundred twenty-three water samples were collected from the air-water syringes, high-speed drills and water sources from 41 dental units in Istanbul, Turkey. The counts of aerobic heterotrophic bacteria and SRB were investigated in the water samples. In addition, the presence of free-living amoebae (FLA) was examined. In this work, we evaluated microbial contamination and reported for the first time the distribution of SRB in DUWLs. We determined that only ten out of 123 water samples were able to meet the American Dental Association's limit (≤200 CFU ml( - 1)). SRB were observed in 102 out of 123 samples (82.9%). In addition, SRB were detected in all of the air-water syringes and high-speed drills. FLA were established in 103 out of 123 samples (83.7%).