Aim: To analyze the influence of a crown fracture without pulp exposure on the risk of pulp necrosis (PN) in teeth with extrusion or lateral luxation injuries.

Material and methods: The study included 82 permanent incisors with extrusion from 78 patients (57 males, 21 females) and 179 permanent incisors with lateral luxation from 149 patients (87 males, 62 females). Twenty-five teeth with extrusion and 33 teeth with lateral luxation had suffered a concomitant crown fracture (infraction, enamel-fracture or enamel-dentin-fracture). All teeth were examined and treated according to a standardized protocol.

Statistics: The risk of PN was analyzed separately for teeth with immature and mature root development by the Kaplan-Meier method, the log-rank test and Cox regression (lateral luxation only). The level of significance was set at 5%. Risk factors included in the analysis: gender, age, crown fracture, and reaction to electric pulp test at the time of injury.

Results: A concomitant crown fracture significantly increased the risk of PN in teeth with lateral luxation. For teeth with immature root development (hazard ratio: 10 (95% CI: 1.1-100) p=0.04) the overall risk was increased from 4.7% (95% CI: 0%-10.8%) to 40% (95% CI: 2.8%-77.2%). For teeth with mature root development (hazard ratio: 2.4 (95% CI: 1.4-4.2) p < 0.001) the overall risk was increased from 65.1% (95% CI: 55.2%-75.1%) to 93% (95% CI: 85.5%-100%).
In teeth with extrusion and mature root development, the overall risk of PN was increased from 56.5% (95% CI: 37.7%-75.4%) to 76.5% (95% CI: 58.9%-94%) in case of a concomitant crown fracture, but the difference was not statistically significant (p > 0.05).

Conclusion: A concomitant crown fracture without pulp exposure significantly increased the risk of PN in teeth with lateral luxation. This risk factor may be used to identify teeth at increased risk of pulp necrosis following lateral luxation injury.