The Dynamic Nature of the Adult Facial Skeleton
While the rapid, formative growth period of adolescence concludes in the late teens to early twenties, the human face is a dynamic structure that continues to remodel throughout life. Instead of a complete cessation of growth, the process shifts from rapid expansion to a slower, more selective form of change involving both bone resorption (loss) and bone deposition (addition). This continuous remodeling impacts overall facial dimensions, proportions, and appearance, a factor increasingly appreciated in fields from orthodontics to aesthetic medicine.
How Facial Bone Remodeling Works
Bone is a living tissue that is constantly being broken down and rebuilt in a process known as remodeling. This process is influenced by genetic and environmental factors and occurs throughout the entire lifespan, including the facial bones.
- Bone Resorption: In some areas of the facial skeleton, bone is lost or resorbed over time. This process is not uniform across the face and tends to concentrate in specific regions.
- Bone Deposition: Conversely, new bone is deposited in other areas, which can cause them to enlarge or change shape. This combination of simultaneous resorption and deposition is what results in the subtle but measurable changes seen in adults.
Region-Specific Changes in Facial Bones After 18
Research using three-dimensional computed tomography (CT) scans has revealed distinct patterns of bone change in different parts of the face as we age. These alterations contribute significantly to the visual signs of aging, such as deepening wrinkles, sagging skin, and changes in overall facial shape.
The Orbitals and Midface
The eye sockets (orbitals) undergo significant changes. Studies show that with age, the orbital aperture tends to increase in size as the bone around the socket's edges is resorbed. The most significant resorption occurs in the inferolateral and superomedial parts of the orbital rim.
In the midface, particularly the maxilla (upper jaw), bone tends to be resorbed, leading to a loss of projection. This reduction in skeletal support can cause the overlying fat pads and soft tissues to shift and descend, contributing to the flattening of cheeks and the deepening of nasolabial folds.
The Mandible (Lower Jaw)
The mandible is one of the most dynamic facial bones in adulthood. Studies have shown continuous remodeling, particularly in males, well into the third decade and beyond. The mandibular angle can change, and bone loss can occur in the prejowl area, further contributing to the appearance of jowls. However, other studies have shown that vertical dimensions can also decrease over time.
The Nose and Brow
Changes in the nasal bones and maxilla can lead to the lengthening and drooping of the nose tip over time. At the same time, the brow ridges may become more prominent in males, while the frontal bone and other areas can also expand or recede.
Comparison of Facial Bone Changes: Adulthood vs. Childhood
| Feature | Childhood/Adolescence | Adulthood |
|---|---|---|
| Primary Driver | Rapid, hormonal growth | Lifelong remodeling (resorption and deposition) |
| Rate of Change | High-velocity, significant change | Slow, subtle, and gradual change |
| Overall Effect | Establishment of adult proportions | Alteration of adult proportions; aging characteristics |
| Maxilla | Expands to accommodate dentition | Resorbs, leading to loss of midface support |
| Mandible | Significant growth and rotation | Continues to remodel, changing angle and support |
| Orbital Area | Increases in size and proportion | Orbital apertures enlarge due to rim resorption |
| Influencing Factors | Genetics, hormones (e.g., GH) | Genetics, hormones, environmental factors, tooth loss, biomechanical forces |
The Role of Biomechanical and Hormonal Influences
Beyond simple aging, several factors play a crucial role in the ongoing changes to facial bones:
- Biomechanical Forces: The mechanical stress from chewing and the movement of facial muscles can influence bone remodeling. Changes in muscle quality with age can alter this stimulation, potentially favoring bone resorption over deposition. A softer, modern diet compared to ancestral diets may also influence the rate and type of craniofacial changes.
- Hormonal Changes: While peak growth hormone levels decline after adolescence, hormones continue to regulate bone metabolism throughout life. Fluctuations, such as those related to pregnancy in women, can influence the rate of craniofacial changes. Conditions like acromegaly, caused by excessive growth hormone, demonstrate the powerful effect hormones have on bone growth, even in adults.
- Genetics and Environment: Both heredity and external factors like sun exposure, diet, and lifestyle contribute to the specific ways an individual's facial structure changes over time.
Clinical and Aesthetic Implications
Understanding that facial bones change after 18 is vital for medical and aesthetic professionals. It provides a more comprehensive view of facial aging than focusing solely on soft tissue, informing treatments for rejuvenation and orthodontic correction in adults. For instance, addressing underlying bone structure through procedures like skeletal augmentation can provide more natural and lasting results than soft-tissue treatments alone.
This evidence refutes the long-held assumption of skeletal stagnation, replacing it with the concept of continuous adaptation. These findings are foundational for contemporary approaches to adult orthodontics and anti-aging treatments. For further in-depth information on bone physiology and remodeling, you can read more at The NIH National Center for Biotechnology Information.
Conclusion: A Lifelong Process
In conclusion, your facial bones do not stop changing after 18. Instead, they enter a continuous, lifelong process of remodeling, which involves both bone deposition and, importantly, selective resorption. These subtle changes, influenced by genetics, hormones, and biomechanical forces, contribute to the alterations in facial proportions and contours we recognize as aging. Understanding this dynamic process provides a more complete picture of how and why our faces change over time.
