Background: The reported risk of pulp necrosis (PN) is low in teeth with concussion injuries. A concomitant crown fracture may affect the risk of PN

Aim: To analyze the influence of a crown fracture (with and without pulp exposure) on the risk of PN in teeth with concussion injury.

Material and methods: The study included 469 permanent incisors with concussion from 358 patients (226 males, 132 females). Among these, 292 had a concomitant crown fracture (70 with and 222 without pulp exposure). All teeth were examined and treated according to a standardized protocol.

Statistical analysis: The risk of PN was analyzed by the Kaplan-Meier method and Cox regression. Risk factors included in the analysis: gender, patient age, root development, type of crown fracture, and reaction to electric pulp test (EPT) at time of injury. The level of significance was set at 5%.

Results: Only one case of PN was observed among teeth with immature root development. The following factors significantly increased the risk of PN in teeth with mature root development: crown fracture without pulp exposure (hazard ratio 4.1 (95% CI: 1.4-11.9), p= 0.01) and negative EPT at the time of injury (hazard ratio 30.7 (95% CI: 7.7-121), p < 0.0001). The overall risk of PN was increased from 3.5% (95% CI: 0.2-6.8) to 11.0 % (95% CI: 5.2-16.7) when a concomitant crown fracture without pulp exposure was present. If the tooth had both a crown fracture and a negative reaction to EPT, the risk was further increased to 55.0% (95% CI: 34.3-75.8).

Conclusion: A concomitant crown fracture without pulp exposure, and a negative EPT at time of injury, significantly increased the risk of PN in teeth with mature root development. These two risk factors may be used to identify teeth at increased risk of pulp necrosis following concussion injury.