How does a D2 interproximal caries compare in dentin vs enamel?

• A. Enamel lesion is more extensive than dentin lesion
• B. Dentin lesion is more extensive than enamel lesion
• C. Dentin and enamel lesions are equal
• D. No dentin involvement

Answer: (B)

When caries progresses beyond enamel, dentin becomes involved and the lesion tends to extend deeper. Enamel is highly mineralized and acts as a relatively strong barrier, so early caries can be limited to enamel. Once the decay reaches dentin, the structure is less resistant because dentin has more organic content and open tubules, allowing demineralization and bacterial spread to continue more readily and reach greater depths. In the D2 stage, the lesion has penetrated into middle dentin, so the dentin component of the lesion is more extensive than any enamel involvement. The other statements conflict with this progression because enamel-only involvement at that depth isn’t present, dentin involvement is already established, and saying there’s no dentin involvement contradicts the D2 designation.