Halachot of Brushing One's Teeth
This is the approved revision of this page, as well as being the most recent.
- It is proper to rinse out one's mouth in the morning so that it is clean in order to pray and praise Hashem 
- If one does not have water or the water is not clean, this rinsing isn't necessary and one should pray nonetheless.
- On a fast day, one may not rinse out one's mouth with water.
- Some poskim recommend to only use toothpaste with a hechsher, while others aren't concerned.
- Shulchan Aruch 4:17 writes that some have the practice of cleaning out their mouths in the morning. Kaf HaChaim 4:59 explains that this is done so that one can have a clean mouth for mentioning Hashem's name (in prayer).
- Kaf HaChaim 4:59, Mishna Brurah 4:37
- Kaf HaChaim 4:59
- OU article writes that because modern tooth pastes are tasty they aren't considered pagum and they're a problem if they have non-kosher ingredients. See there for details.