Egypt's Dar al-Iftaa answers readers' questions in various fatwas. We at See publish these fatwas. The question says:
Is it permissible for fasters to brush their teeth during the fasting hours of Ramadan?
It is permissible to use water and toothpaste during the fasting hours of Ramadan provided nothing reaches the body cavity through a body orifice as this will break the fast. It is better to brush one's teeth at any time other than the fasting hours to remove oneself from Satan's whisperings.
And God Almighty knows best.