A dentist can drill a tooth by many means, either a local anaesthesia or when the patient is serious the dentist has to give even a general anaesthesia. The time of numbness depends on the condition of the patient. If it's only a single tooth that has to be uprooted just because it damaging other teeth close to it, the dentist would just apply a local anaesthesia that would take from 10- 15mins, depending of the patients constitution and the condition of teeth. The doctor/dentist uses general anaesthesia only when he has to conduct a surgery on the patient. Tooth extraction is rarely done these as we can overcome the problem by undergoing root-canal treatment. Extraction is done only in cases of wisdom where rarely the doctor uses a general anaesthesia. The doctor can use any kind of sedative.