All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no objection as regards going to the dentist for a root canal or for a filling of a molar or another tooth even while the patient is fasting but provided he does not swallow anything of the filling product or of the month rinse water…etc. This Fatwa was issued by the High Islamic Council of Fiqh. However, it is safer to treat one’s teeth during the night to avoid any doubts.
Allah knows best.