Radiographic investigation of frequency and location of root canal curvatures in human mandibular anterior incisors in vitro

The aim of the present in vitro study was to evaluate the degree and location of root canal curvatures of mandibular anterior incisors. A total of 396 extracted human permanent anterior incisors (248 central and 148 lateral) were included in this investigation. Exclusion criteria were teeth with extensive carious lesions, restorations, and root canal treatment. The specimens were fixed in a special device and digitally x-rayed (Heliodent MD; Sirona, Benzheim, Germany; Merlin 2.1, Olympus/PerkinElmer, Waltham, MA) with the parallel technique. The distances from the cementoenamel junction (CEJ) to the first curvatures as well as the according angles were recorded. The results were analyzed descriptively, and p values were calculated with the Wilcoxon test. The mean distance between the CEJ and the first curvature of the central anterior incisors was 13.8 mm (standard deviation +/- 2.6) and that of the lateral anterior incisors was 12.3 (standard deviation +/- 2.5), respectively. A total of 82 (33.1%) central and a total of 118 (79.7%) lateral anterior incisors exhibited curvatures. No statistically significant differences between left and right anterior incisors could be observed regarding the canal curvature locations (p < 0.001) and the angle values (p < 0.04). The results showed a high percentage of mandibular anterior incisors with a mean curvature located 13 mm apically from the CEJ. The findings of this study may enhance the predictability of endodontic treatment and minimize errors during post insertion.