Intercommissural line: the line of the mouth corners
Quick facts
- Definition
- Line that joins the two lip commissures, the corners of the mouth.
- Main use
- Horizontal reference to assess the symmetry and tilt of the mouth.
- Comparison
- In general, it runs parallel to the bipupillary line.
- Relevance in orofacial harmonization (HOF)
- Guides the reading of the mouth corners, the smile, and marionette lines.
The intercommissural line is the straight line that connects the right commissure to the left one, that is, the two corners of the mouth. It is used as the horizontal reference of the perioral region, the same way the bipupillary line is used for the eyes.
What is this line for?
Its main function is comparison. When the mouth is tilted relative to the eye line, the face looks misaligned, even if each feature on its own is normal. The comparison also reveals whether one corner is higher, lower, or more retracted than the other, which is frequent and, in many cases, part of natural facial asymmetry.
At rest, the line is usually close to the height of the point where the lips meet. In a smile, the corners rise and the line may curve, which is normal and depends on the action of the elevator muscles and the modiolus.
How does it enter the assessment?
In clinical practice, it is worth observing at two moments:
- at rest, to see the position of the corners and the shape of the lips;
- in a spontaneous smile, to see how the mouth moves and whether one side rises more.
Downturned corners at rest may suggest predominant action of the depressor anguli oris and contribute to the look of marionette lines. The decision to treat, and how, rests with the qualified professional, after assessment, and depends on skin, volume, muscle, and dentition.
Precautions when filling the corners
The mouth corner area has thin skin, intense movement, and nearby vessels. Excessive results tend to look artificial, and a prior asymmetry can become more pronounced if it is not noticed beforehand. Managing expectations is part of the job. The risks of swelling, bruising, nodules, and, more rarely, vascular occlusion exist with any filler, and hyaluronidase must be available when hyaluronic acid is used.
In Harmy
The Mouth Corner point of the marking simulates filler in the area with the volume in ml entered. The simulation starts from a frontal photo at rest and is illustrative; smile dynamics and differences from one side to the other are assessed in person.
Also called: commissural line, mouth corner line.
Frequently asked questions
Does the intercommissural line have to be parallel to the eye line?
In general that is the expected reference, but small tilts are common and natural. What matters is how much the difference bothers the patient and whether there is a functional or head-position component.