The mental foramen (MF) is one of the most consistently used anatomical landmarks in the mandible. It serves as the terminal aperture of the mandibular canal through which the mental nerve, artery, and vein emerge to supply the lower lip, chin, and gingival tissues anterior to the mandibular second premolar.1–3 Accurate knowledge of the MF’s location is essential to avoid injury during local anesthesia, endodontic treatment, implant placement, osteotomies, and reconstructive surgery.4–6

The position of the MF has been reported to vary significantly among populations, races, and even within individuals.7,8 Its location is influenced by genetic, developmental, and functional factors, including alveolar bone resorption, tooth loss, and mandibular growth patterns.9–11 Classically, the MF has been described as lying in line with or below the apex of the second premolar; however, variations include positions between the first and second premolars, posterior to the second premolar, or rarely beneath the canine or molar teeth.12,13

Morphometric evaluation of the MF involves assessing its horizontal and vertical diameters and its relationship to key mandibular landmarks such as the alveolar crest, inferior border, and midline.14–16 These parameters help in identifying safe zones for surgical interventions, minimizing the risk of mental nerve damage. Studies have shown that the mean diameter of the MF ranges between 2 and 5 mm, but population-specific differences exist.17,18

Anatomical studies on dry mandibles provide direct visual and quantitative data free from radiographic distortion and are invaluable for baseline morphometric reference.19–21 In India and other Asian populations, limited osteological studies have systematically documented MF variations in both sides of the mandible. Therefore, the present study was undertaken to analyze the positional and morphometric characteristics of the mental foramen in adult dry mandibles and to compare the right and left sides statistically.

Study Design:

A cross-sectional, descriptive osteological study was performed on 70 adult dry human mandibles (140 sides) obtained from the anatomy department’s osteology collection. Only complete, intact mandibles without gross deformities were included.

Inclusion Criteria:

• Fully ossified, adult mandibles.
• Intact alveolar margins and tooth sockets (dentate or recently edentulous).
• Clearly visible mental foramina on both sides.
• Exclusion Criteria:
• Deformed, fractured, or edentulous mandibles with resorbed alveolar margins.
• Mandibles with pathological bone lesions, cysts, or repairs.

Methodology:

Each mandible was examined for the presence, number, and position of the MF on both sides. The positional relationship of the MF to the mandibular teeth was categorized as:

• In line with first premolar
• In line with second premolar
• Between first and second premolars
• Between second premolar and first molar
• In line with canine/molar

Digital Vernier calipers (accuracy ± 0.01 mm) were used to measure the horizontal (mediolateral) and vertical (superoinferior) diameters at the maximal dimension of the foramen. All measurements were taken thrice and averaged for precision. Bilateral data were recorded separately.

Statistical Analysis:

Data were tabulated and analyzed using SPSS v25. Mean ± SD was calculated for diameters. Bilateral comparison was done using independent t-tests. A p-value < 0.05 was considered statistically significant.

Table 1: Position of the Mental Foramen (n = 140 sides)

Interpretation:
The MF was most commonly located in line with the second premolar on both sides (52.9%), followed by between first and second premolars (16.4%). No foramina were found in line with the canine or molar regions.

Table 2: Morphometric Dimensions of the Mental Foramen

Interpretation:
No statistically significant difference was observed between sides (p > 0.05). The MF tends to be slightly larger horizontally on the right and vertically on the left.

The present study provides essential osteometric data regarding the position and size of the mental foramen in an adult Indian population. The predominance of the second premolar position (52.9%) aligns with the findings of Sankar et al.14, Kalender et al.18, and Al-Shayyab et al.15, who reported similar trends (45–55%). Such consistency suggests a stable evolutionary and functional position related to the premolar apices.

The average horizontal (2.81 mm right, 2.76 mm left) and vertical diameters (2.38 mm right, 2.41 mm left) agree with earlier osteological studies reporting ranges of 2–3 mm.17,18 Absence of significant side variation supports bilateral symmetry, although population-level sexual dimorphism may account for minimal differences reported in other series.20,21

The absence of MF in canine or molar alignment and low frequency between second premolar and first molar (< 10%) corroborates meta-analyses indicating rare posterior displacement in Indian and Asian mandibles compared to Caucasian groups.15,16 Genetic and masticatory loading patterns may explain ethnic variation in MF position.23

Anatomical localization of the MF is indispensable in dental practice. The results of the current study reinforce the need to expect MF near the second premolar region during endodontic and implant procedures. Awareness of such baseline morphometry prevents inadvertent mental nerve injury and ensures effective anesthesia.4,6

The mental foramen was predominantly located in line with the second premolar, with minor positional variations. The mean horizontal and vertical diameters showed no significant right–left differences. These data provide valuable anatomical reference for clinicians performing dental and surgical interventions in the mandibular premolar region.

1. von Arx T, et al. The mental foramen and nerve: clinical anatomy, radiographic features, and surgical considerations. Clin Oral Investig. 2013;17(1):1–9. doi:10.1007/s00784-012-0806-5
2. Al-Shayyab MH, et al. Position, shape, and size of the mental foramen in diverse populations. Dentomaxillofac Radiol. 2015;44(8):20140235. doi:10.1259/dmfr.20140235
3. Sankar DK, et al. Morphometric and positional variations of the mental foramen: a study in dry mandibles. Anat Res Int. 2011;2011:1–6. doi:10.1155/2011/316985
4. Malamed SF. Handbook of Local Anesthesia. 7th ed. Elsevier; 2019.
5. Chrcanovic BR, et al. Anterior loop of the inferior alveolar nerve: a systematic review. Clin Implant Dent Relat Res. 2014;16(4):1–13. doi:10.1111/cid.12088
6. Kalender A, et al. Assessment of the mental foramen location in Turkish adults with CBCT. Surg Radiol Anat. 2012;34(5):367–374. doi:10.1007/s00276-011-0909-4
7. Padmavathi G, et al. Sex estimation using morphometry of the mental foramen. Forensic Sci Int. 2017;275:1–7. doi:10.1016/j.forsciint.2017.03.002
8. Zmyslowska I, et al. Accessory mental foramina: prevalence and dimensions on CBCT. Clin Oral Investig. 2017;21(6):1957–1964. doi:10.1007/s00784-016-1979-z