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Self-Etch vs Total-Etch Depth — NDEB AFK MCQ

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ModerateRestorative DentistrySelf-Etch vs Total-Etch DepthNDEB AFK

A self-etch adhesive primer has a pH of approximately 2.0. How does this compare to the etching effect of 37% phosphoric acid (pH ~0.5)?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: B — Self-etch creates a shallower, less aggressive etch pattern that preserves more of the smear layer and reduces post-operative sensitivity

Self-etch adhesive primers have a higher pH (~1.0-2.5) than 37% phosphoric acid (~0.5), creating a milder, shallower etch pattern. They partially dissolve and incorporate the smear layer rather than removing it completely. This results in less aggressive demineralisation, reduced risk of over-etching and collagen collapse, and consequently less post-operative sensitivity. However, the milder etch on uncut enamel produces lower bond strengths compared to phosphoric acid etching — hence the recommendation for selective enamel etching with phosphoric acid before applying self-etch adhesives.

Reference: Heymann – Sturdevant's Art and Science of Operative Dentistry, 7th ed., 2019