The American Association of Endodontists classifies tooth cracks or fractures into 5 subgroups: craze lines, fractured cusps, cracked tooth, split tooth and vertical root fracture. Cracked teeth were defined as “greenstick” fractures with a history of cold sensitivity and acute pain upon chewing.

The proper treatment of cracked teeth requires a determination of tooth restorability and pulpal status. In teeth with irreversible pulpitis or necrosis, root canal treatment should be undertaken only if the teeth are restorable. Teeth with deep pockets associated with the crack but no other signs of periodontal bone loss are rarely restorable. Whether cracked teeth with necrotic pulps should be treated or extracted remains an open question.

Because long-term studies of treatment outcomes for cracked teeth receiving orthograde root canal treatment in the United States do not exist, Krell and Caplan from the University of Iowa analyzed the 1-year outcomes for such teeth treated by 1 private practice endodontist over a 25-year period. Teeth were filled using the lateral condensation technique and Roth’s 801 sealer. All patients received recall cards 1 year after treatment, at which time they were evaluated for the presence or absence of symptoms, radiographic resolution of previous lesions and the presence of a crown. If no signs or symptoms were seen and any previous pathosis seen on radiographs had resolved with the development of no new pathosis, the treatment was deemed a success.

All teeth included in the analysis had cracks confirmed by direct visualization. Cusp fractures, split teeth and teeth with vertical root fractures were excluded from the analysis. Of the 2086 patients seen with at least 1 cracked tooth, 1406 underwent root canal therapy; 363 patients who returned for follow-up at 1 year were included in the analysis. Success at 1 year was seen in 296 teeth (82%). The 3 variables that best predicted failure were

teeth with marginal ridge cracks

teeth with mesial or distal probing pocket depths of ≥5 mm

periapical diagnosis of chronic apical periodontitis (CAP), suppurative apical periodontitis (SAP) or acute apical abscess (AAA)

Based on these results, the authors created a novel prognostic index (Figure 1) for successful orthograde root canal therapy in cracked teeth, rated from most likely to least likely to succeed:

Iowa stage I: no probing pocket depths ≥5 mm; no crack across the distal marginal ridge

Iowa stage II: no probing pocket depths ≥5 mm; crack present across the distal marginal ridge; no periapical diagnosis of CAP or SAP or AAA

Iowa stage III: no probing pocket depths ≥5 mm; crack present across the distal marginal ridge; a periapical diagnosis of CAP or SAP or AAA

Iowa stage IV: ≥1 mesial or distal probing pocket depth ≥5 mm


Of course, standard treatment methods and technology have evolved over the 25 years covered by this study; for example, the endodontist incorporated nickel–titanium instrumentation 10 years after beginning private practice. Overall, the results of this study suggested that root canal treatment in cracked teeth may have a higher rate of success than had been previously reported.

Krell KV, Caplan DJ. 12-month success of cracked teeth treated with orthograde root canal treatment. J Endod 2018;doi:10.1016/joen.2017.12.025.