The anesthetic used in tooth extraction usually wears off within one to two hours. This is also related to the properties of the anesthetic itself used by the doctor and the method of anesthesia used. It is also related to the individual’s resistance to the drug. The time it takes for the anesthetic to wear off is mainly related to the pharmacological properties of the drug. The longer the half-life of the anesthetic, the longer the duration of action of the drug, and the shorter the half-life, the shorter the duration of effective analgesia. Local anesthetics are usually used for tooth extraction. Lidocaine is more commonly used, and the duration of this drug is probably between one and two hours. There are also drugs known as long-acting local anesthetics, such as bupivacaine and ropivacaine, and these drugs can last up to three hours or even more than four hours due to their long half-life. Doctors can add an appropriate amount of epinephrine to the commonly used lidocaine, which can greatly extend the duration of action of anesthetics, which can generally reach a minimum of 3 hours to maintain the analgesic effect. The addition of epinephrine can play a vasoconstrictor effect, slowing down the metabolism of anesthetic drugs in the local time, thereby extending the duration of anesthesia. Some doctors, considering the patient’s physical reasons, add saline to the anesthetic to dilute the anesthetic concentration. This operation will reduce the duration of analgesic effect. The duration of anesthesia is also related to the resistance of individuals, not everyone can make the anesthetic work or appear to last for several hours, some people may have a very slow onset of anesthesia after the injection, and then the duration of anesthesia is very short, some people are sensitive to anesthesia and do not feel it in the dental cavity for about three minutes after the injection, at this time the procedure can be performed, after which the anesthetic effect disappears for a long time It can last up to two hours. The amount of anesthetic during tooth extraction is relatively small and only plays the role of local anesthesia, mainly to slow down the pain during surgery, which has a very important role in the surgical operation, and a good anesthetic effect is the key to successful surgery.