For a tooth infection, antibiotics can only work if the source of the problem has been eliminated. If your tooth has been root canaled, the infection should disappear if the procedure was a success. If no root canal was done, the source of the infection is the tooth, and it must be extracted. Sometimes a dentist will prescribe antibiotics prior to an extraction in order for the infection to calm down, and then extract the tooth. While you can have a tooth extracted with an infection present, it may be difficult to get fully numb for the procedure, which is another reason to make sure the infection has been lowered with antibiotics before extraction, but you must complete the procedure soon, otherwise the infection will come back and be more resistant to antibiotics.