Hi HouseChick,

If the canker sores are the result of a chronic irritation from a dental appliance.... mouthguard..... partial or full denture.... braces... or poor dental fillings, then the source of the irritation needs to be remedied. If the sores are chronic and they appear for no obvious reason, then an amino acid called L-Lysine if taken daily will help. Canker sores can occur for a variety of reasons. Here is a helpful site as to why they occur and some natural remedies to try as well.
http://www.healingdaily.com/conditions/canker-sores.htm

Hope you get some relief soon!

Bryanna