My son swallowed the flouride at the dentists. what can this do?

Nausea: The most likely issue is nausea and or vomiting, if your son swallowed enough fluoride. There should not be a long term issue.

Nothing really: It was a miniscule amount, and it happens now and then. He would need to swallow a whole lot of the topical gel for there to be any consequence. He probably only swallowed a few drops.

Nothing: No long term effect, was probably a minimal amount and only a single occurrence. Long term excess Fluoride can cause tooth discoloration, so your dentist will carefully balance Fluoride treatments, Fluoride toothpaste, Fluoride mouth rinses, and ingested Fluoride (vitamins or drops) to give maximum protection from cavities without discoloring the teeth. Follow dentist's recommendations exactly.