Location and dimensions of the mental foramen: a radiographic analysis by using cone-beam computed tomography.

Introduction: The mental foramen (MF) is an important landmark in dentistry. Knowledge of its position is central to perform block anesthesia of the mental nerve or to avoid nerve damage during surgical procedures in the premolar area of the mandible. The present radiographic study aimed at evaluating the location and dimension of the MF and measuring distances to neighboring structures by using limited cone-beam computed tomography (CBCT).

Methods: Sagittal, axial, and coronal CBCT images of 142 patients (26 bilateral and 116 unilateral cases) were retrospectively screened to determine the location of the MF with respect to adjacent teeth and to take linear measurements of the size of the MF and its distances to the upper and lower borders of the mandible. In addition, the course and angulation of the mental canal exiting the MF were assessed.

Results: The majority of MF (56%) were located apically between the 2 premolars, and another 35.7% of MF were positioned below the second premolar. On average, the MF was localized 5.0 mm from the closest root of the adjacent tooth (range, 0.3-9.8 mm). The mean size of the MF showed a height of 3.0 mm and a length of 3.2 mm; however, individual cases showed large differences in height (1.8-5.1 mm) and in length (1.8-5.5 mm). All mental canals exiting the MF demonstrated an upward course in the coronal plane, with 70.1% of the mental canal presenting an anterior loop (AL) in the axial view. The mean extension of AL in cases with an AL was 2.3 mm.

Conclusions: This study is consistent with previous radiographic studies regarding size and location of MF and distances between MF and adjacent anatomic structures. The assessed bilateral cases showed a high intraindividual concordance for certain features when comparing right and left sides.