Teeth can be damaged by dental decay, fractures or other reasons. This exposes the pulp to bacteria from saliva that may irritate it. Unless treated the problem may increase and symptoms such as pain and swelling can occur as the nerves and blood vessels become progressively more damaged and eventually the pulp space becomes completely infected with bacteria. An inflmmatory response to the bacteria occurs resulting in damage to the bone around the root, often appearing as a dark shadow on a dental radiograph.
Once this problem occurs there are only two ways to resolve it, either extract the tooth or carry out a procedure called root canal treatment or Endodontic therapy. Antibiotics cannot resolve the problem as there is no longer a blood supply entering the pulp space to reach the bacteria and deliver the antibiotic.