The appropriate space maintainer for a 3-year-old patient who nursed exclusively and has extensive rampant caries after traveling 1.5 hours is:

Correct answer: D. Silver diamine fluoride (SDF)

• A. Extraction without space maintenance leads to space loss and is not appropriate without considering the child's developmental needs.
• B. Stainless steel crowns require cooperation and preparation — not appropriate for an extremely uncooperative 3-year-old after a long trip.
• C. Lingual holding arch requires the primary molars to already be missing — this patient still has the teeth with caries.
• D. Correct. Silver diamine fluoride (SDF) is the best option for a very young, uncooperative patient with extensive rampant caries. It arrests caries, is painless to apply, requires no preparation, and is the most appropriate non-invasive option for early childhood caries in this scenario.