yes plaque can build up. the white on your tongue is plaque buildup. I've researched this and mentioned it before, it's not candida that we all thought originally. If you are a mouth breather, then waking up on the morning will transfer that build up of (bacteria)plaque to where the lips meet(try visualize what i mean) or if you have dry mouth then the plaque(bacteria) will build up in the mouth also. The acidophilus will get rid of this. PLaque is a word specifically for buildup on the teeth, i don't no the word for buildup anywhere else in the mouth, but let's just call it plaque or bacteria/same thing. of course that white line can also be dead skin soaked in saliva.