Can you suggest tips for a stubborn canker sore underneath the tongue?

Sure about that?: Are you sure it's a canker sore? There is not much you can do to make them heal quicker. Avoid hot and spicy foods, you can rinse with salt water or use any number of remedies from your local pharmacy, but only to make them feel better meanwhile. Some dentists use lasers for treatment. See a dentist and have it looked at for more help.

Alternative:Licorice: Licorice has been used since ancient times to treat canker sores in the mouth. Also, small studies show it can be effective when used as a mouthwash -- 50-75% improvement in 1 day. http://tinyurl.com/kr9aeau sucking on dgl lozenges may work also. Other studies showed positive results with a dissolving licorice disk placed on the sore. http://tinyurl.com/mdvde3o.