The Mental Foramen: Part I-Size, Orientation, and Positional Relationship to the Mandibular Second Premolar

By Phillips J., Weller N., Kulid J.

Date: 01/1990
Journal: JOE


To report the average size, orientation, and position of the mental foramen in relation to the second MD premolar.


  • N= 75 dry, adult mandibles (age, sex, race were unknown).
  • Foramina were measured from the center (C) to the nearest 0.1 mm with Boley gauge.


  • Left side foramina larger, on average, than the right; average size 5 x 4 mm.
  • Usual location of exit in a posterior-superior direction (90 %).
  • Most common location was inferior to the crown of the second premolar (63 %), and about 60 % the distance from buccal cusp tip to the inferior border of the mandible (A-B).
  • Slight M or D positioning to A-B, but entire foramen within 5 mm of this line.

Clinical Significance:

  • Mental block should enter soft tissue posterior-superior to mental foramen along the long axis of the 2nd premolar and be advanced anterior-inferior until mental foramen guides the needle.
  • Vertical releasing incisions should be avoided around the MD second premolar to avoid mental nerve damage.