Ruling on anaesthetic injections and cleaning, filling or extraction of teeth whilst fasting

Praise be to Allah.

The things mentioned in the question do not have any effect on the validity of the fast, rather they are forgiven, but he should be careful to avoid swallowing any medicine or blood. Similarly the injection mentioned does not have any effect on the validity of the fast, because it is not like food or drink, and the basic principle is that the fast remains valid. End quote. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him)