Fluoride is an active ingredient in many toothpastes because it repairs light damage to your teeth by restoring tooth enamel. Rinsing with an over-the-counter fluoride mouthwash once daily can decrease sensitivity, stopping the pain you feel. If the fluoride rinse feels good but isn't enough, a stronger varnish is available from your dentist. Ask your dentist about coating your teeth in a fluoride varnish to treat sensitivity [source: Zamosky]. This takes only a few minutes to apply. Your dentist might want you to have periodic coatings and may also prescribe a high-fluoride mouthwash [source: Mayo Clinic].
But beware of non-prescription mouthwashes or those your dentist doesn't recommend. Some contain as much enamel-eroding acid as many acidic foods and drinks.