What is the best way for a young child to get flouride for their teeth, daily supplements or topical foam at the dentist's office?

Both: If by dailey supplements you mean the ingestible kind, you should ask your dentist first because too much ingested Fluoride can actually hurt you. This kind only helps forming teeth. The topical kind helps teeth already in the mouth.

Different tasks: Daily supplements convert tooth enamel as it forms (permanent teeth begin forming before birth) into a more decay-resistant form. Topical Fluoride treatments strengthen the outer surface of the enamel after the teeth have erupted. They do different things. Your child needs both unless your water supply is already fluoridated. Ck w your dentist, he'll know.