Morphometric study for the localization of the mental foramen in relation to the vertical reference plane

The mental foramen (MnF) is the anatomic landmark where the mental neurovascular bundle exits the mandible. Precisely determining the position of the MnF is necessary before all dentoalveolar therapeutic procedures performed in the mandibular premolar area.

For the study, we performed two ex vivo direct morphometric determinations on dry human dentate and edentate mandibles, and two in vivo imaging morphometric determinations through cone-beam computed tomography (CBCT) and orthopantomography (OPG) in dentate human patients. The following landmarks were used to locate the MnF: the distance between the MnF and the superior border of the mandible (MnF-SB), the distance between the MnF and the inferior border of the mandible (MnF-IB), and the position of the MnF in relation to the root apices of the posterior teeth. The results obtained from these data were processed statistically using the analysis of variance (ANOVA).

By direct morphometry on dentate mandibles, the MnF was situated closer to the IB and by direct morphometry on completely edentulous mandibles, the MnF was located closer to the SB. In both direct morphometry studies, the MnF transverse diameter was larger than the vertical one, with the MnF having an oval shape. ANOVA for both direct morphometry studies showed that the distances MnF-IB and MnF-SB significantly vary statistically with interactions and depending on age (p<0.00001). The vertical diameter of the MnF significantly varies statistically depending on age, interactions and between studies, and its transverse diameter varies statistically significantly with interactions and depending on age (p<0.00001). According to OPG and CBCT imaging studies, the MnF was located closer to the IB, and the transverse diameter of the MnF was larger than the vertical diameter; such results are similar to the direct morphometry study performed on dry dentate human mandibles. Regarding the position of the MnF in relation to the root apices, it was most frequently located inferior to the root apices in 79.45% of cases, in 19.23% of cases it was located at the root apices level and in 1.31% of cases it was located superior (coronal) to the root apices. ANOVA for both imaging morphometry studies showed that the MnF-IB distance varies statistically significantly with the interactions, the study, the sex of the patients and their age, the MnF-SB distance varies statistically significantly with the interactions, the study and the patients' age (p<0.05), and the MnF diameters vary statistically significantly with interactions and patient age (p<0.05).

The results of this study can help dental practitioners in improving dentoalveolar surgery procedures in the posterior mandible.