My radiation Oncologist and my dentist told me to use a fluoride gel, preferably in trays (like football players use to protect their teeth) for 10-15 minutes EVERY DAY.

Reading these posts, I'm not going to skip many days.

Although, it seems that the fluoride coats the inside of my mouth and makes my dry mouth worse for several hours afterwards; so, I try to do this just before bed, as I breath through my mouth at nite.