An indentation that appears in the cheek when a person smiles, commonly called a dimple, is an anatomical feature present in a minority of the population. These cheek dents are not a result of bone structure or a lack of tissue, but rather a slight variation in the facial musculature and connective tissue that develops during the embryonic stage. This natural physical variation creates the distinct, temporary depression that appears when the face is in motion.
The Anatomy Behind the Dent
The primary muscle involved in creating a cheek dimple is the Zygomaticus Major, which is responsible for pulling the corners of the mouth up and back when you smile. In most people, this muscle originates at the cheekbone and runs as a single band, inserting into the corner of the mouth (modiolus). In individuals with a dimple, however, this muscle often exhibits a structural anomaly known as a bifid or double Zygomaticus Major muscle.
This variation means the muscle splits into two distinct bundles as it travels toward the mouth. One bundle inserts normally at the corner of the mouth, while the second, inferior bundle inserts slightly lower and has fibers that adhere directly to the overlying dermis. This attachment of the muscle fibers to the skin is known as a dermal tethering effect.
When the Zygomaticus Major muscle contracts during a smile, the inferior bundle shortens and pulls on the point where it is tethered to the skin. This localized pull causes the skin to be drawn inward, creating the temporary indentation recognized as a dimple. The depth and shape of the resulting dent are determined by the length and strength of this muscular attachment and the amount of subcutaneous fat in the area.
Classifying Cheek Dimples by Location
While the classic dimple is often located in the mid-to-lower cheek area, close to the corner of the mouth, the specific query regarding “upper cheek dents” points to a less common location. The traditional form is typically positioned on a line running from the outer corner of the eye to the corner of the mouth. This common placement is directly related to the lower insertion point of the bifid Zygomaticus Major muscle.
Upper cheek dimples, sometimes referred to as malar dimples, appear higher on the face, often near the cheekbone, or malar region. These higher-set indentations may be caused by fascial attachments or variations in other muscles of facial expression located higher up, such as the Orbicularis Oculi muscle. The appearance of these higher dimples can sometimes present as a longer, crease-like fold rather than a small, circular dent, depending on the length of the fascial attachment.
The position of the dimple dictates its visibility and shape. Lower-angle dimples appear closer to the mouth, whereas upper cheek dents involve muscular or connective tissue variations situated higher on the cheek, nearer to the zygomatic arch.
Genetics and Development of Dimples
The tendency to have cheek dimples is generally considered a heritable trait that runs in families, although the exact genetic mechanism is more complex than once thought. Historically, dimples were described as a single-gene dominant trait, meaning only one parent needed to carry the gene for a child to inherit the feature. Current research suggests a more nuanced inheritance pattern, likely involving multiple genes, or a polygenic trait, which accounts for the variety in dimple appearance and presence.
The development and visibility of these facial indentations also relate closely to a person’s age and facial fat distribution. Many infants have temporary dimples due to a greater volume of subcutaneous fat in their cheeks, commonly known as baby fat. As a child grows and the facial fat diminishes or remodels, these initial indentations may disappear entirely.
For those with the underlying muscle variation, the dimples may remain permanent, but even they can change in prominence over a lifetime. Changes in weight and the natural loss of skin laxity that occurs with aging can either make the dimples more apparent or cause them to become less noticeable.