A strong and well-defined jaw angle confers a certain degree of masculinity. Some men have it naturally, while others seek to obtain it from synthetic implants. The jaw angle makes up a portion of the mandibular ramus and its outline is formed by the intersection of its outer posterior and inferior borders. This bony intersection, or angle, can be anywhere from 90 to 120 degrees. The closer the angle is to 90 degrees, the more visible and pronounced the jaw angle appears. This occurs because the bony ramus is more developed vertically and lengthens the position of the jaw angle point to a lower position.
As the jaw angle becomes more acute (closer to 90 degrees), its lower position becomes closer to the horizontal plane of the lower border of the chin. The relationship of the jaw angle and chin points is known as the jawline or in cephalometric terms the mandibular plane. While the mandibular plane is a term originally used in the context of one’s occlusion (bite), it has a direct relationship to the aesthetics of the jaw angle. The more steep the mandibular plane angle, the less prominent the jaw angle becomes. The more horizontal the mandibular plane angle, the more prominent the jaw angle.
The one dimension of the jaw angle that is more obscure, but no less significant, is its width. How much does it stick out or flare? Also known as bigonial width, a prominent jaw angle usually will have more width at the jaw angle point. This width significantly affects the shape of the face, giving it a more square appearance as it gets wider.
Understanding the aesthetics of the jaw angle has great relevance when helping a patient decide how much change to make. (i.e., implant selection) While there are numerous styles of jaw implants from several different manufacturers, the key issues to look at are the amounts of ramus lengthening and width changes. A panorex or cephalometric x-ray analysis is helpful as direct measurements can be made on them but there are certain anthropometric (visual) parameters as well.
When it comes to lengthening the ramus or jaw angle point, you usually do not want it to end up at a horizontal level below the lower border of the chin. In other words, you don’t want a reverse mandibular plane angle. I would argue that most men don’t want it exactly at the same level either. That would make most faces too square and unnatural looking. The jaw angle point should be just a little above the chin in both frontal and side views. That provides an aesthetic sweep to the jawline from front to back. Look at most male models and you will see that jawline feature. I certainly have had patients who want to be fairly square but they fully recognize this more extreme type jaw look and are aiming for it.
When it comes to jaw angle width, this belies an exact measurement. But visually you can relate it to the width of the zygomatic arch in a frontal view. A prominent jaw angle in men is wider than the arch width. For women, it should usually be at or just inside a vertical dropdown line from the arch. But men need to be beyond this line. How much is a matter of personal preference but never beyond the outer helix of the ear.
In planning for jaw angle implants, a panorex x-ray can be helpful to determine whether and how much lengthening of the jaw angle is needed. For width estimation, a frontal photograph is more helpful than any x-ray.
Dr. Barry Eppley
Indianapolis, Indiana