Smear Layer — NDEB AFK MCQ
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Correct answer: E — A microscopically thin layer of organic and inorganic debris created by mechanical preparation of dentin
The smear layer is a 0.5-5 μm thick layer of organic and inorganic debris (ground dentin, collagen, bacteria, odontoblastic processes) created on the dentin surface by mechanical instrumentation (burs, hand instruments). It plugs the dentinal tubule orifices (smear plugs), reducing dentin permeability. In restorative dentistry, total-etch systems remove the smear layer; self-etch systems incorporate it. In endodontics, NaOCl+EDTA removes it for better sealer adaptation.
Reference: Heymann – Sturdevant's Art and Science of Operative Dentistry, 7th ed., 2019