Restorative & Materials · single question
What is the recommended etch time for ENAMEL using 37% phosphoric acid for composite resin bonding?
Show answer and explanation
Correct answer: C. 15–20 seconds
Standard etch time for enamel with 35–37% phosphoric acid is 15–20 seconds. Dentin should be etched for 10–15 seconds. Over-etching dentin collapses collagen and weakens the hybrid layer.
- A. 5–10 seconds is insufficient — won't create adequate microporosities for resin tag penetration.
- B. 30–45 seconds over-etches enamel and can weaken the bond.
- C. CORRECT. 15–20 seconds for enamel is the standard. Creates the 'frosty' etched appearance needed for bonding.
- D. 60 seconds causes severe over-etching of both enamel and dentin — never recommended.
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