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.

Material and methods: The study included 82 permanent incisors with extrusion from 78 patients (57 male, 21 female) and 179 permanent incisors with lateral luxation from 149 patients (87 male, 62 female). A total of 25 teeth with extrusion and 33 teeth with lateral luxation had suffered a concomitant crown fracture (infraction, enamel fracture or enamel-dentin-fracture). All the 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 were gender, age, crown fracture, and response to electric pulp test at the initial examination.

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% confidence interval (CI): 1.1-100] P = 0.04), the overall risk 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 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 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 PN following lateral luxation injury.