Mental symphysis: the anterior junction of the mandible
- Nerve
- Highlighted area
Quick facts
- Definition
- Line where the two halves of the mandible join, at the midline of the chin.
- Development
- The halves are separate at birth and fuse in the first years of life.
- Neighboring structures
- Mental protuberance, mentalis muscle, pogonion and menton.
- Relevance in facial harmonization
- Defines the midline of the chin, a reference for symmetry and chin position.
The mental symphysis is the region where the two halves of the mandible join, at the front, exactly at the midline of the chin. At birth, the mandible is made of two pieces connected by fibrous tissue. They fuse into a single bone over the first or second year of life, and the point of fusion is the symphysis.
Where is it and what surrounds it?
On the front of the chin, the symphysis corresponds to a subtle vertical line in the bone. Over it and around it develops the mental protuberance, the triangular relief that forms the bony base of the chin. Below, the region ends at the landmarks used in profile.
| Landmark | Position |
|---|---|
| Pogonion | Most anterior point of the bony chin |
| Menton | Lowest point of the symphysis outline |
| Gnathion | Midpoint between pogonion and menton, used in measurements |
On the inner surface, the symphysis has small projections (the mental spines) where muscles of the tongue and the floor of the mouth attach. None of these details is visible or easily palpable, but they make up the deep design of the region.
Why does the midline matter?
The line of the symphysis defines the center of the chin and is the reference for assessing symmetry. When the chin looks deviated, the first question is whether the deviation comes from the bone, the position of the teeth, the musculature or an asymmetry of soft tissue. Comparison with the facial midline and with the position of the incisors helps separate these causes.
A deviation of the symphysis from the center of the face usually has a skeletal origin and is not corrected with filler. The product may change the perception of the contour, but it does not change the position of the bone.
What does facial harmonization need to remember?
The chin is a frequent injection site. Branches of the submental artery and the mental nerve run through it, the latter exiting through the mental foramen on the side. The mentalis muscle, which attaches just below the incisors, moves the skin of the chin and takes part in expression.
As in any vascular area, the consent should mention swelling, bruising, asymmetry and, more rarely, vascular complications, and hyaluronidase must be available when the product is hyaluronic acid.
Also called: mandibular symphysis, symphysis menti.
Frequently asked questions
Is the mental symphysis the same as the chin?
No. The symphysis is the line where the two halves of the mandible fuse. The bony chin is the mental protuberance, which forms in the region of the symphysis, and the visible chin also includes muscle, fat and skin.