Eli,

I'll try to answer as best I can - I am familiar with the trays-I have mine. But, my answer won't be real technical.

Before beginning radiation your doctor should insist you see a dentist. My radiation oncologist sent me directly to the oral surgeon. Radiation to the mouth has the potential to kill the salivary glands. It this happens you become very prone to tooth decay. (the moisture aids in keeping placque from forning.) Since you don't have salivary glands anymore, you run the risk of fracturing jaw bones with any major dental work after radiation. Any dental work that has to be done - you have to be treated in a hyperberic chamber first.
They will fit you for flouride trays and give you a flouride toothpaste 1.1%. I am on teeth cleaning every 3 months. Although I will say that I have not been able to use the trays yet after radiation, due to the fact the flouride burns my throat. I am told this will get better. The flossing and toothpaste is helping keep my teeth healthy. I now brush 2-3 times a day.
They wanted to pull all my teeth and we made the decision that I couldn't try and maintain my weight with no teeth. For me it was the right decision to only lose 14 teeth. My dentist tells me due to really good care for the past 7 months, I have stopped the progress of gum desease. It just takes determination and developing new habits.

I'm sure there is something I forgot to tell you and someone will come along that can supply you with more information.

Take care,
Dinah