title: Dental unit waterline contamination and its possible implications during periodontal surgery.
abstract: BACKGROUND
  Dental unit waterline contamination has become a concern to clinical dentistry. This concern arises from the fact that bacteria sloughed from established biofilms in dental unit waterlines increase heterotrophic bacteria counts in water exiting these units.
  
  
  METHODS
  Scanning microscopy and bacterial viability staining were used to examine the sessile and planktonic biofilm present in dental unit waterlines and water samples, respectively. In addition, the limulus amebocyte assay was used to measure the lipopolysaccharide (LPS) levels in water samples.
  
  
  RESULTS
  All dental unit waterlines were coated with a well-established biofilm made up of filamentous and bacillus-like microorganisms. Water samples collected from these dental units contained high numbers of individual bacteria and bacterial aggregates. A viability staining technique identified significantly more bacteria in water than could be cultured, and 64% of the total bacterial population stained as nonvital. Since the bacterial load (viable and nonviable) was high, we examined the LPS in dental unit water samples. The mean LPS levels in water collected from high-speed and air/water lines in use were 480 and 1,008 endotoxin units (EU)/ml. This was significantly higher than the mean level of 66 EU/ml found in water samples collected from adjacent clinic sinks. The LPS level at the start of the day (2,560 EU/ml) was reduced by 70% with 1 minute of flushing (800 EU/ml). Flushing times of 5 and 10 minutes were not able to reduce LPS levels to zero.
  
  
  CONCLUSIONS
  The presence of high heterotrophic bacterial counts, sloughing biofilm, and high LPS levels are discussed in relation to patient risk and periodontal wound healing biology.
authors.affiliation: Department of Oral Biological and Medical Sciences, University of British Columbia, Faculty of Dentistry, Vancouver. putnins@interchange.ubc.ca
authors.forename: E E
authors.initials: EE
authors.lastname: Putnins
authors.forename: D
authors.initials: D
authors.lastname: Di Giovanni
authors.forename: A S
authors.initials: AS
authors.lastname: Bhullar
mesh_terms: D000704:Analysis of Variance; D001419:Bacteria / Q000145:classification; D018441:Biofilms; D015169:Colony Count, Microbial; D004396:Coloring Agents; D003748:Dental Equipment / Q000382:microbiology*; D003754:Dental High-Speed Equipment / Q000382:microbiology; D004731:Endotoxins / Q000032:analysis; D004866:Equipment Contamination; D006801:Humans; D019552:Infection Control, Dental; D008033:Limulus Test; D008070:Lipopolysaccharides / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D010510:Periodontal Diseases / Q000601:surgery*; D012044:Regression Analysis; D012307:Risk Factors; D013223:Statistics as Topic; D014867:Water / Q000032:analysis; D014871:Water Microbiology; D014945:Wound Healing
chemical_list: D004396:Coloring Agents; D004731:Endotoxins; D008070:Lipopolysaccharides; D014867:Water