Failure of endodontically treated teeth: classification and evaluation.

All endodontically treated teeth that were extracted over a 1-yr period in a busy group practice were evaluated for cause of failure. The 116 teeth collected were classified into major failure categories of prosthetic, periodontic, and endodontic origin. Of the teeth, 59.4% were prosthetic failures which were due primarily to crown fracture. Teeth that had been crowned had greater longevity than uncrowned teeth. Periodontal failures constituted 32% of the study. Only 8.6% of the failures were due to endodontic causes, but these failures became evident more quickly than those in the other categories. A classification of failures is presented, and the results are analyzed.