white stuff on his end teeth

4^th week of radiation and 2^nd chemo therapy

My husband is just done with his 2^nd chemo therapy, and almost done with 4^th week of radiation. He is doing fairly fine accept heavy mouth shore. He is eating everything by tube and drinking water by mouth.

He was compiling white stuff on his end teeth and I am not sure what it is!!

Does anyone know what is white stuff on his teeth might be?

 He his brushing twice a day and try to floss as it’s almost impossible to do due to he can’t open his mouth.

Thanks you so much for your help. Hetal