What invalidates fasting in the field of dentistry, and what is exempt when necessary?

Fasting, linguistically, means abstention. Legally (in Sharia), it means abstaining from things that break the fast, with an intention, from dawn until sunset. These things that break the fast are:

1. Eating and drinking intentionally, and swallowing anything that reaches the throat and stomach from the mouth. 2. Ejaculation of semen while awake, with customary pleasure or through masturbation. 3. Sexual intercourse. 4. Intentional vomiting. 5. Water reaching the throat due to excessive gargling or sniffing water up the nose, and instillation (of drops into the nose). 6. Apostasy. 7. Hesitation in the intention. 8. Using nourishing injections and solutions. 9. Enema if it reaches the stomach. It is stipulated for all of these that one performs them willingly, not under duress.

Examining teeth, cleaning them, and filling them does not break the fast if nothing reaches the stomach. As for tooth extraction, it is preferable for it to be done outside fasting hours, unless there is an urgent need.