During treatment of root surface caries, which type of dentine should be left undisturbed rather than excavated and restored?

Correct answer: C. Eburnated (sclerotic) dentine

• A. Softened demineralised dentine on the surface of an active lesion should be excavated.
• B. Carious dentine at the enamel-dentine junction is removed as part of caries excavation.
• C. CORRECT. EBURNATED or SCLEROTIC dentine is the tooth's own successful defence. Tubules have been occluded by mineral deposition, producing a surface that is hard, dark, shiny and impervious. This represents an ARRESTED lesion. Excavating it removes sound, protective tissue and needlessly approaches the pulp; the correct management is to leave it, control the caries risk, and monitor.
• D. Infected dentine is soft, wet and bacterially contaminated and must be removed.

Note: The clinical test is tactile: an arrested root lesion feels HARD and leathery to a sharp explorer and appears dark and glossy. An active lesion feels soft and tacky and appears light brown and matte.