Wisdom teeth are the last molars to come through, usually in the late teens or early twenties. When there is not enough room they can grow at an angle, stay partly buried or push against the next tooth — all reasons a dentist or oral surgeon may recommend removal.
You will usually have an x-ray or scan first so the surgeon can see the position of the tooth and its roots, and decide how difficult the removal will be. Simple extractions take minutes under local anaesthetic; impacted teeth may need a small surgical approach and, sometimes, sedation.
Mild swelling and soreness for a few days is normal. If pain gets worse after the third day, or you notice fever or a bad taste, contact the clinic — that can be a sign of a dry socket or infection. In Tokyo most clinics give clear aftercare instructions in writing, which is worth following to the letter.