What is the ruling on a fasting person visiting the dentist for treatment, and what is the ruling on someone who, while fasting during a Ramadan day, has something go down his throat and swallows it unintentionally during a visit to the dentist?

Cleaning teeth, filling them, or extracting them does not affect the validity of the fast. However, one should be careful not to swallow any medicine or blood. Likewise, a tooth anesthetic injection does not invalidate the fast because it is not in the meaning of eating and drinking. If it is possible to go to the doctor at night, that would be preferable.