I can't guess what is right for you, but when I got my fluoride trays my dentist told me that during rad treatments you can go from 0 cavities to a whole mouthful in a very short time. Rad on the face/neck area decreases saliva, and decreased saliva leaves a breeding ground for plaque. He told me plaque is sticky and without saliva to cut it, it clings to teeth and really amps up your risk of cavities. I notice for myself, since my tongue is so sore, I can't do the normal "tongue-scoop" of excess food like I used to. Not that I can eat much anymore, mind you.

but anyhow, I plan to keep using the fluoride as long as I can. My dentist recommended 30 minutes a day, and if I need to I'll drop the time I spend with the trays in.

Good luck, Marilyn!! Got my fingers crossed for you!