title: Evaluation of gram negative bacterial contamination in dental unit water supplies in a university clinic in tabriz, iran.
abstract: OBJECTIVE
  Bacterial contamination of dental unit water supplies (DUWS) has attracted a lot of attention in recent years due to the emergence of serious infectionsin susceptible dental patients. The aim of the present study was to evaluate the presence of gram-negative bacterial contamination in DUWS at Tabriz University of Medical Sciences Faculty of Dentistry.
  
  
  METHODS
  This descriptive study was carried out on 51 active dental units in different departments. Con-tamination was determined by taking samples from the unit's water supply before dental procedures and the use of specific culture media. The cultures were evaluated after 48 hours.
  
  
  RESULTS
  Gram-negative bacterial contamination was identical in all the departments. In the departments on the ground floor, namely Departments of Periodontics and Oral and Maxillofacial Surgery, Pseudomonas contamination was observed in 71% of units; in the departments on the first floor, namely Departments of Prosthodontics, Orthodontics and Pedodon-tics, 46.8% of the units had Pseudomonas contamination; and in the departments on the second floor, namely Departments of Operative Dentistry and Endodontics, 37.7% of the units demonstrated Pseudomonas contamination.
  
  
  CONCLUSIONS
  Gram-negative bacterial contamination was evident in the evaluated DUWS. The contamination type was identical but the number of contaminated units decreased with the increase in the height of the floors.
authors.affiliation: Assistant Professor, Department of Oral Medicine, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Firoz
authors.initials: F
authors.lastname: Pouralibaba
authors.forename: Esrafil
authors.initials: E
authors.lastname: Balaei
authors.forename: Atabak
authors.initials: A
authors.lastname: Kashefimehr