Surgical-anatomical evaluation of mandibular premolars by CBCT among the Italian population

The thorough knowledge of the anatomy of mandibular premolars is an essential factor for a correct approach to endodontic treatment, concerning both non-surgical and surgical treatment.

Since there is no data on the Italian population in this context, the aim of this study was to evaluate, from a surgical perspective, the anatomy of mandibular premolars among the Italian population through a cone-beam computed tomography (CBCT) analysis, considering the morphology of their root canals according to Vertucci's classification and the prospect of their apices with regard to the vestibular bone plate and the proximity to the inferior alveolar nerve and the mental foramen as well as to evaluate the most appropriate distance from the apex in the radicular resection (3 mm or 5 mm).

At total of 492 CBCT acquisitions (from 246 males and 246 females) were included retrospectively, evaluating 720 mandibular premolars. Age, gender, the tooth position in relation to the vestibular plate, the number of roots, the tooth length and the root length, the number of canals, the configuration of the root canal system according to Vertucci's criteria, C-shaped canals, the distance from the cementoenamel junction (CEJ) to the canal bifurcation, the number of apical foramina, and the distance from the apex to the inferior alveolar nerve or the mental foramen were evaluated.

The study highlighted the frequent anatomic variability of the root canal system. It found the presence of 1 root for first and second premolars in 97% and 99% of cases, of 2 roots in 2.7% and 0.7% of cases, and of 3 roots in 0.3% and 0.3% cases, respectively. In 92% of cases, the mental foramen was located below a second premolar, or between a first premolar and a second premolar; only in 8% of cases, it was located close to a first premolar, but never as close as to a second premolar.

Mandibular premolars show a truly surprising anatomical variability, especially for mandibular first premolars, which therefore requires adequate radiographic planning before providing any endodontic treatment, or especially endodontic retreatment or endodontic surgery. Taking into account proximity to the inferior alveolar nerve and the mental foramen, any surgical approach must be carefully planned. Frequently, a two-dimensional (2D) radiographic examination is not sufficient to fully understand the anatomical variability of these teeth.