Radiographic investigation of location and angulation of curvatures in human maxillary incisors.

The aim of this radiographic study was to evaluate the degree and location of root canal curvatures of human maxillary incisors. A total of 286 extracted human maxillary incisors (145 central and 141 lateral incisors) were included in this investigation. Exclusion criteria were teeth with extensive carious lesions, restorations, and root canal treatment. For this in vitro study, the teeth were fixed in a special device and digitally x-rayed with the parallel technique. The distances from the cementoenamel junction (CEJ) to the first curvature and the according angle were recorded. The results were analyzed descriptively, and p values were calculated with the Wilcoxon Mann-Whitney test. The mean distance between the CEJ and the first curvature of the central maxillary incisors was 10.4 mm (standard deviation [SD] +/- 2.8) and that of the lateral incisors was 11.1 mm (SD +/- 3.0). Most of the central incisors (right: 94.2%, left: 98.7%) and all of the lateral incisors exhibited curvatures. Statistically significant differences between central and lateral maxillary incisors could be observed regarding the canal curvature locations (p = 0.016) and the angle values (p < 0.001), but there was no statistical difference between the right and the left side. The results showed the high percentage of root canal curvatures in maxillary incisors with a mean curvature located 10.7 mm apical from the CEJ. These findings are important to minimize failures during post insertion.