What is the angle formed by cavity walls and external tooth surface?

• A. Dentin-enamel angle
• B. Cavosurface angle
• C. Occlusal angle
• D. Gingival angle

Answer: (B)

The cavosurface angle is the angle formed at the margin where the prepared cavity walls meet the external surface of the tooth. This interface—where the cavity meets enamel at the outside of the tooth—is exactly what the question is describing, so this term is the precise name for that angle. It’s distinct from internal tooth interfaces like the dentin-enamel angle, which describes the inside boundary between dentin and enamel; the occlusal angle, which pertains to the chewing surface geometry; and the gingival angle, which refers to the margin near the gum.