@tfrap369
I would ask my pharmacist what if any medications can increase production of saliva, I believe there are some. I used Biotene but there are other OTC remedies. Also, have a serious talk with your dentist, be persistent, The same with your other doctors, don't let the subject drop until they offer you a solution that you're happy with. Remember your doctor, dentist, pharmacist, etc. are working for you not the other way around. If your physicians aren't willing to address your problems either get a second opinion or change doctors.
Have you always been on mono therapy? If so perhaps a combination might work. I assume you've had seizures since you say “only drug that worked for me was Keppra.”
Do you have tonic-clonic seizures?
Take care and be strong,
Jake