Associations between the 3D position of the mental foramen with sagittal skeletal relationships (classes I, II, and III) and vertical facial growth patterns (normal, long, and short faces) in different ages and sexes: a retrospective cohort study of 360 CBCTs.

BACKGROUND

The 3D position of the mental foramen (MF) is of significant clinical value in dental implantology and mandibular surgeries or in local anesthesia. Despite its importance, it is not clearly known how the position of MF can alter in different individuals, since the literature on the associations between the MF position with vertical growth patterns is non-existent and those on links between the MF position and skeletal malocclusions are scarce. Therefore, we aimed to investigate these, for the first time, on cone-beam computed tomographies (CBCTs).

METHODS

Archival CBCTs of 9 sub-groups (i.e., 3 skeletal Classes I, II, and III × 3 vertical growth patterns 'long face, short face, normal face') were collected by evaluating patients' SNA, SNB, ANB, facial angle, lower facial height, and FMA (n = 9 × 40 = 360). Included cases were older than 17 years and without any history of orthodontic/orthognathic treatments (243 women, 117 men, mean age: 22.28 ± 2.80 years). Perpendicular distances between the MF and 3 fixed bony structures (the mandibular symphysis [S/width], the mandibular ramus [R/length], and the mandibular lower cortex [C/height]) were measured on different sectional planes on both hemimandibles. Left- and right-side measurements were combined. Data were analyzed using the 3-way ANCOVA, Bonferroni, one-way ANOVA, Tamhane, Pearson, and t-test (α = 0.05).

RESULTS

Width was the smallest in Class II and greatest in Class III cases (all P values < 0.000001, Bonferroni). It was the shortest in long faces and longest in short faces (all P values ≤ 0.00008). The inferior-superior height was larger in Class III than both Classes I and II (both P values ≤ 0.003); there was no significant difference between Classes I and II in terms of height (P = 0.684). Height was the largest in long faces and smallest in short faces (all P values < 0.000001). The anterior-posterior length was the largest in Class III and smallest in Class II (all P values < 0.000001). Length was larger in short-face people versus normal- or long-face individuals (P ≤ 0.00003); nevertheless, long and normal faces did not differ in terms of length (P = 0.448). Subjects' age was not correlated with their MF positions (P ≥ 0.579, Pearson coefficient). Sex dimorphism existed only for height (P = 0.009, t-test) but not for length or width.

CONCLUSIONS

The MF position may considerably differ in various horizontal or vertical growth patterns and sexes. This should be noted in mandible surgeries.