A full command of the anatomy in any area of intended injection vastly decreases the probability of adverse events and greatly increases the injector’s confidence.
The skin of the chin is some of the thickest on the face mobile dental unit.2 Dermal thinning, which occurs most rapidly in postmenopausal women,3 may cause the skin of the chin to adopt an orange peel appearance—hence the name “peau d’orange.” This results from hypertonicity of the mentalis muscle that connects to the dermis via dense fibrous septae.
The face contains discrete fat compartments that, with age, experience volume decreases and increases in a nonuniform manner.4
Unlike the muscles of mastication, which have bidirectional boney attachments, the muscles of facial expression are connected to the overlying skin via a layer called the superficial musculo-aponeurotic system (SMAS). When a facial muscle contracts, the overlying skin moves with it dental curing light.
Vascular supply to the chin arises from two main branches of the facial artery: the inferior labial artery and the submental artery. Likewise, venous drainage is accomplished via the inferior labial vein and submental vein and ultimately to the jugular vein. Lymphatic drainage of the chin is principally to the ipsilateral submental lymph nodes.
Location of the mental foramen is somewhat variable. Anatomical studies show that in 50% of cases, the mental foramen is immediately buccal to the second bicuspid Dental Chair. In 25% it’s found between the first and second premolar, and in the remaining 25% it’s found posterior to the second premolar. The foramen’s vertical location, even in the senescent mandible, is greater than 8 mm superior to the inferior border of the mandible.5
Aging results from intrinsic and extrinsic factors. Intrinsic factors include loss of collagen and volume loss from both fat and bone. Extrinsic factors include smoking, photodamage, and pollution.
Downturned oral commissures imply a loss of lip volume leading to an inferomedial curling of the commissure that dissolves into the marionette line. Presentation is magnified by a greater muscular pull from the depressors than the elevators of the corner of the mouth. A common complaint from patients presenting for facial rejuvenation is that their family members tell them they “look sad or annoyed.”
Genetics, loss of fat volume, skeletal remodeling, dermal thinning, and ptotic skin all contribute to marionette lines. Perimental hollows result from fat depletion, dermal thinning, and bony resorption.6
The prejowl sulcus forms a notch bilaterally on the mandibular border, located at the caudal terminus of the marionette lines. This sulcus is due to a combination of soft-tissue atrophy and bony resorption.7
A hyperactive mentalis muscle produces a pebbled and irregularly textured appearance of the chin integument. Sustained hypertonicity creates a permanent labiomental groove that is highly resistant to dermal filler treatment without concomitant treatment with neurotoxin.
Continuous observation and study of average, unattractive, and beautiful faces, both young and old, is the way to master clinical evaluation for diagnosis and treatment of patients seeking facial injectable treatment. The ability of the practitioner to detect details eluding the untrained eye is fundamental to providing clinical excellence.