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Infection Control · single question

What is the CFU (colony-forming unit) threshold that triggers evaluation of dental waterlines?

  1. More than 200 CFU/mL
  2. More than 800 CFU/mL
  3. More than 500 CFU/mL
  4. More than 1000 CFU/mL
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Correct answer: A. More than 200 CFU/mL

CDC and ADA guidelines recommend dental unit waterlines maintain <200 CFU/mL of heterotrophic bacteria — the same standard as EPA drinking water. Water exceeding 200 CFU/mL requires treatment and re-testing. 500 CFU/mL is the maximum for some guidelines but 200 is the dental standard. 800 and 1000 are too high.

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