Combination injuries 1. The risk of pulp necrosis in permanent teeth with concussion injuries and concomitant crown fractures

Abstract

The reported risk of pulp necrosis (PN) is low in teeth with concussion injuries. A concomitant crown fracture may affect the risk of PN. To analyze the influence of a crown fracture (with and without pulp exposure) on the risk of PN in teeth with concussion injury. The study included 469 permanent incisors with concussion from 358 patients (226 male, 132 female). Among these, 292 had a concomitant crown fracture (70 with and 222 without pulp exposure). All teeth were examined and treated according to standardized protocol. The risk of PN was analyzed by the Kaplan-Meier method and Cox regression. Risk factors included in the analysis: gender, age, stage of root development, type of crown fracture, and response to electric pulp test (EPT) at the initial examination. The level of significance was set at 5%. The risk of PN was low in teeth with immature root development [1.1%, 95% confidence intervals (CI): 0-3.4]. 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 no response to EPT at the initial examination [hazard ratio 30.7 (95% CI: 7.7-121), P < 0.0001]. The overall risk of PN 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 gave no response to EPT, the risk further increased to 55.0% (95% CI: 34.3-75.8). No response to EPT at the initial examination or a concomitant crown fracture significantly increased the risk of PN in teeth with concussion injury and mature root development. If both risk factors were present there was a synergetic effect.