The Split Tooth – A Cracked Tooth Gone Bad

 There are various factors that could influence long-term prognosis in endodontics. It is our duty to provide appropriate postoperative care for patients. A recent study¹ shows that success rates of modern endodontic treatments are as high as those of implant surgery in the long run, thanks to advanced technology and materials used in endodontics. The significant finding reported from comparing implant and endodontic cases was that implants required more postoperative treatments to maintain them.

     In spite of the high success rates in endodontics, some of the cases will fail over time, even if the root canal therapy is performed perfectly. Common causes of postoperative failures are coronal leakage, root fracture, root resorption, and endo-perio complications. There is one thing in common among those causes: abnormal occlusal forces on a tooth can be a cause of failure in endodontic treatment. Wilcox, et al² showed that canal enlargement of 40% to 50% of the root width increased susceptibility to vertical fracture. It has also been shown that attempts at removal of separated files usually result in the removal of a large amount of root dentin, which ends up reducing the root strength by 30% to 40%, leading to possible fracture later on.³ Root fracture occurs, depending on the crown-root ratio and anatomical features of the tooth, and the amount of remaining root dentin. Patients’ habits of mastication such as clenching and grinding are also considered to relate to root fracture by abnormal occlusal forces. The more favorable the crown-root ratio, the better the tooth can withstand masticatory forces, and the better the prognosis. Teeth with short, slender, and/or tapering roots have a poorer prognosis than those with long and broad roots. Multirooted teeth usually resist traumatic forces better than single-rooted teeth. Flared molar roots give better support than fused, conical roots. Broad occlusal tables and large crowns can contribute to increased mobility. The support of the tooth is determined by the height of the alveolar crest and the length and shape of the root. Canines can withstand loss of support better than lateral incisors by virtue of their longer roots and root concavities. Maxillary first premolars show early mobility because of the tapered roots. Some patients have teeth with short roots and others have root resorption, both of which have often been seen as a result of orthodontic therapy. Such teeth are less resistant to excessive occlusal forces which play key roles in root resorption and root fracture. Accordingly, orthodontic therapy and bruxism contribute to those phenomena.