My son has been on MTX since the summer and is doing well. I have noticed however, that it is hard to keep his teeth clean, and I am wondering if it might have something to do with his immune system being suppressed. I've noticed he has been getting orange coloured stains on his front teeth over that last several weeks. Yuk! I have been able to remove most of it when I do his teeth, but within a day it returns. I Googled it-it's plaque! Perhaps he is lacking good bacteria in his mouth which would keep the bad bacteria at bay? We keep very good care of his teeth-brushing at least twice a day, flossing daily, and using a fluoride rinse. He does not drink juice, is not fond of candy, and does not snack often. (He does eat fresh fruit twice a day however, and drinks 2 cups of milk a day.) He has annual check-ups and professional cleanings, and has never had a cavity. Does anyone know why this is happening and if there is a solution?