37% phosphoric acid for ____ seconds

• A. 5 seconds
• B. 15 seconds
• C. 30 seconds
• D. 60 seconds

Answer: (A)

Etching time with 37% phosphoric acid is about controlling how deep the enamel is demineralized to create the right level of micromechanical bonding. A brief etch of five seconds is enough to produce the necessary enamel roughness for many bonding systems while minimizing mineral loss and the risk of sensitivity. Longer times (15, 30, or 60 seconds) remove more enamel minerals, create a deeper demineralized layer that may not be fully infiltrated by resin, and can weaken bond durability or increase sensitivity. In the scenario implied by the question, five seconds provides the balance between adequate bond formation and preserving enamel integrity. Always follow the adhesive system manufacturer’s instructions, as times can vary with different products.