A tooth is infected when the pulp (where the nerve tissue and blood supply lives) of the tooth has had bacteria introduced into the system. Depending on how much tooth structure remains, the only solutions are: root canal therapy or extraction. Not all infected teeth will produce pain. Some chronic infections happen without the patient even knowing! But it is not safe to wait on treating an infected tooth. Not only can the infection possibly start causing pain and/or severe swelling, there is risk of the bacteria spreading to other parts of your head and ultimately to vital organs of your body.