How to prevent gag reflex at the dentist?

Numb: With viscous xylocaine (lidocaine) or have the dentist numb the gag reflex area.

Rinsing: Rinsing with a strong mouthwash or a strong salt water solution just before a dental appointment can help with gagging.

Salt: Salt on the tip of the tongue a topical numbing agent towards the back of the soft palate in more severe cases nitrous oxide (laughing gas) a more natural approach that is sometimes used is accupuncture to the tragus of the ear.

Spray: A small spray of a topical anesthetic, as Benzocaine or similar into the pharynx (back of throat) can help minimize the reflex.

Nitrous oxide: I have found that using nitrous oxide gas helps. However in extreme cases I have used sedation dentistry to put patients to sleep with high hag reflexes.