Where is a D3 interproximal caries located in the dentin?

• A. Outer third
• B. Middle third
• C. Pulp chamber
• D. Inner third

Answer: (D)

In dentin, depth is described in thirds from the pulp outward. The deepest layer, closest to the pulp, is the inner dentin. A D3 interproximal caries means the decay has penetrated into that inner dentin, near the pulp, but is still in dentin rather than in the pulp chamber itself. So the correct location is the inner dentin near the pulp.