Steve,

Mouth sores are one of the most unwelcome side effects of chemo and radiation. These treatments target rapidly growing cells. The lining of the mouth and oral cavity is and area where cells rapidly replace the existing ones. There are multiple entities that can cause the sore ness and ulcers that can occur together or individually. A few that come to mind are: apthous ulcers, thrush, inflammatory hyperplasia, mucositis (more common with radiation than chemo), traumatic ulcers, and immunodeficiency (cuased by the chemo and on occasion not).
There is no "magic wand" and every patient is different and will have a different solution be their best friend to help reduce or control mouth sores.

Some things you can do, and you may already know these are,
Drink lots of water.
Avoid caffeine, alcohol in all forms and tobacco.
Avoid acidic, course (chips etc.) and spicy foods.
Be extremely diligent in your oral hygiene routine.
See your dentist, a rough tooth or filling that rubs your lips or cheek can remove or weaken the mucous membrane and actually cause and/or make the ulcers worse.
Your dentist can also recommend rinses or other medications that can help reduce the discomfot and pain.

I have in the past fabricated smooth, almost mouthguard like trays, for pateints to wear just to keep their teeth from contacting their cheeks and lips due to the fragile situation with the lining of their mouths.

Biotene, and Closys have products that can help.

I hope this is of some use to you.

E-mail me anytime.

My prayers and thought are with you.

Mike