Hi,
Since your mother is experiencing pain, the sooner you can get her to an experienced do tor, the better. Have you phoned her doctor and asked for advice? Pain management is important and your mother's needs should be addressed as quickly as possible.

You didn't mention where your mother is being treated. Please make sure that it is at a comprehensive cancer center.

You can locate these centers at the OCF's website:
http://www.oralcancerfoundation.org/resources/cancer_centers.htm

Although it may be a long distance from where you live to one of these centers, it is the way to get the best possible treatment and advice.

The best care may not necessarily be the closest. - Sheldon