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Restorative & Materials · single question

For how long is hydrofluoric acid applied to etch a lithium disilicate (e.max) crown intaglio surface?

  1. 15 seconds
  2. 20 seconds
  3. 60 seconds
  4. 5 minutes
Show answer and explanation

Correct answer: C. 60 seconds

  • A. 15 seconds is too short for lithium disilicate.
  • B. ~20 seconds is the etch time for weaker feldspathic porcelain, not lithium disilicate.
  • C. Correct. Lithium disilicate is etched with ~5% hydrofluoric acid for about 60 seconds (20 s for feldspathic).
  • D. 5 minutes would over-etch and weaken the ceramic.

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