Hi... the flouride can be VERY irritating. I know they say take it at night, before bed, but after rads ( I did it during but only until it became too painful then I stopped), I eased into it doing it every second night at first, then nightly and sometimes if it's too irritating I switch to days for a bit that way after an hour I can rinse. Which you wouldn't necessarily do if you do it before bed. There are some that are more neutral than others, and mint, particularly if it's strong hurts. Ask him to recommend another brand. I had my recent check up almost one year out and the dental oncologist said my mouth was great for all it had been through - but I don't eat sugar or processed foods and I water pik twice a day to clean along the gum line... I think all of this helps... good luck.