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

By Phillips JL, Weller RN, Kulild JC

Date: 01/1990
Journal: JOE

Summary:  

Purpose:

to report the size and orientation of the mental foramen as well as its positional relationship to the mandibular second premolar.

n: 75 human mandibles with intact teeth from left 2nd Pm to right 2nd Pm, intact B-cusps of 2nd Pm, and reasonable teeth position and alignment.

Materials and Methods:

 Measurements were made directly on both sides of mandibles using Boley gauge. The external circumference of each mental foramin were outline by pencil on the lateral side of the mandible. A vertical line was drawn form the B cusp tip of 2nd Pm  to the inferior border of the mandible (AB line). •The size of the mental foramin was measured by the greatest horizontal and vertical dimensions.

•Orientation: The direction of exit of each mental canal was recorded.

•The Horizontal position of the mental foramen was recorded as mesial, intersecting, or distal to the reference line AB.

•The distance CD was measured from the center of the foramen perpendicular to line AB and this distance was recorded as being either mesial, intersecting, or distal to the reference line.

•Vertical position was determined by the distance from the buccal cusp tip of the mandibular second premolar to the level of the center of the foramen (line AD) and from the cusp tip to the inferior border of the mandible (line AB) was measured and recorded.

•The average ratio of the distances (AD/AB) was calculated.

Most Highlighted Results:

⁻Average horizontal dimension was 4.6 mm. The average vertical dimension was 3.4 mm (oval shaped). 

⁻ The average distance from the AB line to the center of the foramen was approximately 2-mm mesially or distally.

⁻ The average ratio of the distance from the buccal cusp tip to the center of the foramen vs. the distance to the inferior border of the mandible (AD/AB) was 60.6%.

Clinical Significance:

The accumulated data from this study can also be useful in administering LA for a mental block. The

needle should enter the soft tissue posterior and superior to the mental foramen at a point located below the clinical crown and along the long axis of the second premolar. That point is usually located 60% of the distance from the buccal cusp tip of that tooth to the inferior border of the mandible.