What is the best treatment?

Correct answer: B. Stainless steel crown

• A. SDF arrests caries and is valuable for non-restorable teeth, pre-cooperative children or as an interim measure — but it does not restore form or function in a heavily broken-down tooth, and it stains the lesion black.
• B. Correct. A primary molar with extensive/multi-surface caries — particularly one where a previous restoration has already failed — is best restored with a STAINLESS STEEL CROWN. Full coverage protects the remaining tooth structure, has far superior longevity to a large multi-surface intracoronal restoration, and reliably maintains arch space until exfoliation.
• C. A large multi-surface amalgam in a broken-down primary molar has a high failure rate; the case states amalgam has already been attempted.
• D. Composite is technique-sensitive, requires good moisture control, and is not the restoration of choice for extensive caries in primary molars.

Note: Also check the pulpal status. Extensive caries in a primary molar frequently requires a pulpotomy BEFORE the stainless steel crown is placed.