title: An investigation of the microbial contamination of dental unit air and water lines.
abstract: OBJECTIVE
  The objective of this study was to measure the microbial contamination released from dental unit air lines (DUAL) and dental unit water lines (DUWL).
  
  
  METHODS
  Emissions from DUAL and DUWL from five dental units supplied by a central water source (tap) and a centralised air supply were sampled three times over a five- week period. Air was forced through sterile water and then plated onto selective agar using apparatus designed to spread the sample solution evenly, and then incubated at room temperature for seven days. Colonies were then counted and the concentration of bacteria present was determined and expressed as colony forming units per millilitre (cfu/ml) per minute. The same procedure was used to evaluate five other dental units, which had attached independent water reservoir (bottle) systems (IWR). Only deionised water was added to the bottles and unit waterlines were cleaned weekly with alkaline peroxide based solution. Values were expressed as cfu/ml.
  
  
  RESULTS
  Air and water specimens obtained from dental units supplied with tap water had microbial counts significantly (t-test, p < 0.05) greater than IWR dental units.
  
  
  CONCLUSIONS
  Results indicate that IWR can reduce the numbers of micro-organisms released from DUWL. However, the effectiveness of such systems should be routinely monitored. Emissions from DUAL seems to reflect the levels of microbial contamination present in DUWL.
authors.affiliation: University of Birmingham Dental School, St. Chad's Queensway, Birmingham B4 6NN, UK.
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Walker
authors.forename: F J Trevor
authors.initials: FJ
authors.lastname: Burke
authors.forename: Chris H
authors.initials: CH
authors.lastname: Miller
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Palenik
mesh_terms: D000391:Air Microbiology; D000468:Alkalies / Q000627:therapeutic use; D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification*; D015169:Colony Count, Microbial; D019551:Dental Disinfectants / Q000627:therapeutic use; D003748:Dental Equipment / Q000382:microbiology*; D004203:Disinfection / Q000379:methods; D004866:Equipment Contamination / Q000517:prevention & control; D006801:Humans; D016555:Matched-Pair Analysis; D010545:Peroxides / Q000627:therapeutic use; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D000468:Alkalies; D019551:Dental Disinfectants; D010545:Peroxides