For many injectors, rejuvenation of the face using hyaluronic acid (HA) often begins with establishing a foundation in the middle third (zygomatic-malar region). After that, contouring is created posteriorly via treatment of the temples and mandible, and anteriorly via the chin.
According to the Scheideman method, the chin and mandible belong to the lower third of the face, where the distance from the oral commissure (Sto) to the chin apex (Gn) correspond to two-thirds of the total lower third height.
In women, the perception of attractiveness is usually due to the upper facial features; however, the lower third is important, as sagging skin in this region creates the stigma of aging. In men, a strong lower third is a marker of masculinity; their attractiveness lies in the lower third of the face, where strong jawlines and chins are ideal. It is also important to consider that there are gender differences regarding the chin. The male chin is flatter and wider, while the female chin is pointed and narrower.
Inherent Abnormalities
Whe
n it comes to the profile, the facial convexity angle (G-Sn-Pg) is a useful evaluation tool. Ideally, the angle should stay between 165° and 175°.
Micrognathia, a bone abnormality where the lower jaw is undersized, occurs in 1 in 1,500 births. Normally, horizontal and vertical micrognathia coexist. Retrognathia, or receding chin, is an abnormal posterior placement of the mandible.
A common complaint of patients with micrognathia or retrognathia is a double chin. Often, these patients may come seeking treatment of “submental fat,” but they actually need treatment for a weak chin.
Patients with a weak chin normally present with chin cellulitis, which corresponds to the excessive contraction of the mentalis muscle, that is rotated anterosuperiorly.
When injecting the chin with HA, the injector must consider two concepts: myomodulation and rebuilding the lacking bone.
Practitioners can inject six different anatomical regions of the chin with varying objectives according to the patient’s needs as follows:
Improving Chin Height
Labiomental Fold: Using a cannula, inject a high G’ (G prime) HA at the superficial subcutaneous layer, using a fanning technique, 0.3 to 0.7 mL on each side. The point of entrance is lateral to the marionette line. By doing this, you start to push the mentalis muscle down. The objective is to reduce lip protrusion, provide support to the oral commissure, and elongate the chin. It is important to avoid using an excessive amount of HA in this area, since you are not just modulating the mentalis muscle but also the depressor labii inferioris (DLI) and the depressor anguli oris (DAO).
Chin Apex: At the same point of entrance for the labiomental fold – aiming at the chin apex – inject a high G’ HA with a cannula, or a needle, at the deep subcutaneous or bone layer, using a bolus technique – 0.2 to 0.3 mL on each side. The objective is to improve the vertical dimension of the chin.
Improving Chin Width
Lateral Chin: With a needle, inject a high G’ HA at the bone using a bolus technique – 0.1 to 0.2 mL on each side, following a line down the oral commissure. The objective is to widen the chin. This should be applied only to male patients.
Improving Chin Projection
Pogonion Soft Tissue: Inject a high G’ HA perpendicularly with a needle using a bolus technique (1 bolus or 3 separate boluses in a triangle shape) – 0.1 to 0.3 mL centrally, at the bone or deep subcutaneous. The objective is to improve chin convexity.
Prejowls and Mandible Anterior Portion (be- low the chin apex): Inject a high G’ HA with a cannula at the subcutaneous layer, using a linear retrograde injection technique; 0.5 to 1 mL. The objective is to rectify the mandible and advance its anterior portion to improve the facial convexity angle.
Of course, not all of your chin injection patients will require treatment of all of these areas. Proper and individualized evaluation is mandatory.
After seven years of applying this technique, the average volume of HA that I inject for chin treatments is 4 mL. If more volume is needed, it is preferable to schedule another session within a few months, to allow the acclimatization of the product and the stretching of the tissues to achieve more volume, especially in women. This recommendation is intended to help you avoid undesirable complications like severe endurance and myomodulation, and/or the emergence of local telangiectasia.
The recommended HAs for chin injection are those with a high G’, a good vertical projection, and last over 18 months.
Finally, one interesting observation to keep in mind is that treatment of the chin is often an indication from the injector, not from the patient, since patients normally do not recognize their weak chin or realize the importance of the chin to optimal facial contouring.
About the Author
Silvia Zimbres, MD
Dr. Zimbres completed her medical residency in dermatology at the Universidade de São Paulo (São Paulo, Brazil). She is the owner and leading practitioner at Clinica Doux, which is known for providing pathologic, oncologic and surgical dermatology. Her clinic also offers the most modern treatments with lasers, intense pulsed light, radiofrequency, HIFU, Coolsculpting, botulinum toxin, biostimulators and HA fillers. Dr. Zimbres is passionate about aesthetics. Since 2014 Dr. Zimbres has been training dermatologists and plastic surgeons not only in Brazil, but all over the world, about injectables in theoretical and hands-on workshops. Her mission as a teacher is to prepare injectors to deliver satisfaction and joy to their patients with safety and natural outcomes.