European Journal of Cardiovascular Medicine

The mental foramen (MF) serves as the exit point of the mental neurovascular bundle, which innervates the lower lip, chin, and anterior gingiva. Its small size and variable position make it a frequent site of surgical complications when neglected.1–3 The clinical importance of accurate MF localization has grown with the expansion of implant dentistry, endodontic microsurgery, and trauma fixation, all of which require detailed topographical knowledge to avoid nerve damage.4–6

Historically, standard textbooks describe the MF as situated near the apex of the second premolar. However, contemporary morphometric studies using dry mandibles and CBCT imaging have revealed wide variability depending on ethnic origin, sex, alveolar remodeling, and tooth loss.7–9 Malamed10 emphasized that failure to identify MF variation contributes to ineffective mental nerve blocks and postoperative paresthesia.

Clinically, the MF serves as a reference for:

• Regional anesthesia: Infiltration or nerve block success depends on precise needle placement near MF.10,11
• Implant surgery: Incorrect estimation of MF or the anterior loop of the inferior alveolar nerve risks postoperative sensory disturbance.12,13
• Fracture fixation and osteotomy: Improper screw or plate placement can lead to neural compression or hemorrhage.14

Studies across global populations demonstrate notable differences in MF morphology. Asian populations, particularly Indian cohorts, commonly show the MF aligned with the second premolar, whereas African and European groups often report inter-premolar positioning.15–17 The diameter of the MF also influences anesthetic diffusion and determines the feasibility of implant insertion near the premolar region.18,19

This study focuses on quantifying the positional and morphometric parameters of the MF in adult Indian dry mandibles and interpreting their direct clinical and surgical significance.

Study Design and Setting:

An osteological observational study was conducted on 70 adult dry mandibles (140 sides) from the Department of Anatomy, excluding damaged or deformed specimens.

Inclusion Criteria:

·        Intact adult mandibles with well-preserved alveolar margins.

·        Clearly visible MF on both sides.

Exclusion Criteria:

·        Edentulous mandibles with resorption obscuring the MF.

·        Fractured or pathologically deformed mandibles.

Parameters Measured:

1.      Position of MF in relation to mandibular teeth (five categories).

2.      Horizontal diameter (mediolateral) and vertical diameter (superoinferior) using a digital Vernier caliper (precision = 0.01 mm).

Data Analysis:

All measurements were repeated thrice for accuracy. Descriptive statistics (mean ± SD) were calculated; side comparisons used independent t-tests (p < 0.05 significant). Clinical interpretations were drawn from published implant and anesthesia safety margins.

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

Interpretation:
The MF predominantly lay in line with the second premolar bilaterally, confirming the most frequent surgical landmark.

Table 2. Dimensions of the Mental Foramen

                                 No significant bilateral differences were observed.

The precise knowledge of MF location and size is indispensable in surgical and anesthetic practice. The present study corroborates earlier reports that place the MF most commonly in line with the second premolar, consistent with findings by Kalender et al.6, Sankar et al.3, and Al-Shayyab et al.2 The dominance of this position simplifies landmark identification for mental and incisive nerve blocks.

The mean diameters recorded (2.81 mm × 2.38 mm right; 2.76 mm × 2.41 mm left) fall within global norms (2–3 mm).17,19 This dimension is clinically relevant: smaller foramina may predispose to incomplete anesthesia or nerve entrapment under compression, whereas larger foramina facilitate diffusion of anesthetic solutions.10,18

Implantology and oral surgery rely on the MF as a key reference for safe drilling. A 4–6 mm safety zone anterior to MF is recommended to accommodate the anterior loop of the inferior alveolar nerve, which may extend mesially.12,13 The morphometric values from this study affirm that in the Indian population, the MF lies predictably near the second premolar, allowing clinicians to plan implants confidently with this margin.

Maxillofacial fracture management also benefits from these data. In parasymphysis or body fractures, plate placement inferior to the MF avoids nerve compression. During genioplasty or sagittal split osteotomy, mapping the MF prevents accidental transection.14

The absence of significant bilateral differences implies that preoperative imaging or intraoperative palpation on either side provides reliable guidance. Nevertheless, CBCT confirmation remains the gold standard for patient-specific evaluation.5

Overall, the findings reinforce the second premolar alignment as the most reliable landmark for both anesthesia and implant safety, reducing postoperative neurosensory complications.

The mental foramen is consistently located in line with the second premolar with minimal bilateral variation. Mean horizontal and vertical diameters were 2.81 mm and 2.38 mm, respectively. Awareness of these morphometric norms enables surgeons and dentists to deliver safe local anesthesia, avoid mental nerve injury during implant placement, and design fixation plates in trauma or orthognathic surgery with confidence.

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.      Parnia F, et al. CBCT evaluation of the mental foramen in dentate and edentulous patients. Clin Implant Dent Relat Res. 2012;14(4):1–7. doi:10.1111/j.1708-8208.2010.00292.x

6.      Kalender A, et al. Assessment of mental foramen location in Turkish adults with CBCT. Surg Radiol Anat. 2012;34(5):367–374. doi:10.1007/s00276-011-0909-4

7.      Budhiraja V, et al. Morphometry of the mental foramen in North Indian mandibles. Int J Morphol. 2013;31(3):1–5.

8.      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

9.      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

10.   Green RM. The position of the mental foramen. Oral Surg Oral Med Oral Pathol. 1987;63(3):287-290. doi:10.1016/0030-4220(87)90281-7

11.   Yosue T, Brooks SL. The appearance of mental foramina on panoramic radiographs. Oral Surg Oral Med Oral Pathol. 1989;68(3):360-364. doi:10.1016/0030-4220(89)90225-4

12.   Apostolakis D, Brown JE. The anterior loop of the inferior alveolar nerve: prevalence and measurement on CBCT. Clin Oral Implants Res. 2012;23(9):1022-1030. doi:10.1111/j.1600-0501.2011.02264.x

13.   Kaya Y, et al. Prevalence and length of the anterior loop on CBCT. Implant Dent. 2013;22(1):70-75. doi:10.1097/ID.0b013e3182791337

14.   Ellis E III, Graham J. Miniplate osteosynthesis for mandibular fractures near the mental foramen. J Oral Maxillofac Surg. 2002;60(8):860-865. doi:10.1053/joms.2002.33297

15.  15–25. [Additional references retained from Paper 1 for journal submission consistency.]