Factors that break and don't break the fast

Dental treatment while Fasting

Q: I am a dentist. A fasting patient requires urgent treatment e.g. extraction or draining abscess.

Will this be permissible while fasting? Bear in mind that an injection is required, blood flows from the extraction site, and water may be put into the patient's mouth. Will the fast need to be repeated?

Masturbation whilst Fasting

Q: 

  1. Does masturbation nullify the fast?

  2. If it does nullify the fast, does this person have to stay without eating and drinking for the rest of the day?

  3. When he takes ghusl, will he just rinse his mouth and nose or will he gargle his mouth properly and put water properly in his nose?