Short answer
Craniofacial growth is shaped by both genetic blueprinting and functional influences — including breathing patterns, tongue posture, chewing forces, and muscle activity. Research beginning with Moss's Functional Matrix Theory established that soft tissues and functional demands, not genes alone, drive how bone grows and remodels during childhood. Environmental and behavioral factors during the growth years can meaningfully affect the size, shape, and structure of the face and jaw.
Craniofacial growth is influenced by biology, environment, function, airway, posture, and growth direction. This page summarizes the major scientific concepts behind modern facial development in plain language.
How the Maxilla and Mandible Grow
The craniofacial skeleton does not grow uniformly. Different regions — the cranial base, the maxilla (upper jaw), and the mandible (lower jaw) — grow at different rates, in different directions, and are influenced by different biological signals.
The maxilla grows primarily through a process called bone deposition and resorption, guided by the nasal septum and surrounding soft tissues. The mandible grows through elongation at the condyles and remodeling along its surfaces.
Importantly, these growth processes are not purely genetic. As the Functional Matrix Theory (Moss, 1969) established, the soft tissues and functional demands surrounding skeletal structures — including muscles, airways, tongue posture, and breathing patterns — exert powerful influence over how bone grows and remodels. The growth of the face is a dynamic interplay between genetic blueprint and environmental input.
Why Width, Forward Position, and Vertical Balance All Matter
One of the most clinically significant aspects of craniofacial growth is its direction. Ideally, the maxilla and mandible grow forward and laterally, creating a broad midface with adequate tongue space, a well-supported airway, and balanced facial proportions.
Balanced (Forward) Growth
- Broad, well-developed dental arches
- Adequate tongue space and nasal airway
- Strong cheekbone and chin projection
- Balanced facial proportions
- Room for all teeth, including wisdom teeth
Vertical (Downward) Growth
- Narrow, V-shaped or constricted arches
- Reduced tongue space; compromised airway
- Flat midface with recessed chin
- Long lower face height
- Crowding, impacted teeth
Landmark research by Björk (1963, 1983) using metallic implants demonstrated that mandibular growth rotation varies substantially between individuals. Some faces rotate forward (favorable), while others rotate backward and downward (unfavorable), with profound effects on facial form and occlusion.
The maxilla occupies the center of the face and serves as the structural foundation for the nasal airway, the orbital floor, and the upper dental arch. When the maxilla is underdeveloped transversely (too narrow), it restricts nasal airflow and reduces tongue space. Vertically, if it descends excessively rather than growing forward, it increases lower facial height and narrows the pharyngeal airway.
Airway and Breathing
The relationship between craniofacial growth and airway health is bidirectional. An underdeveloped or vertically excessive midface compromises the airway, and a compromised airway — through mouth breathing and altered posture — further worsens facial growth patterns.
Research has shown that nasal obstruction during growth leads to measurable changes in facial morphology, including increased lower facial height, narrower arches, and posterior mandibular rotation. Maxillary expansion has been demonstrated to improve nasal airway volume, reduce mouth breathing, and in some cases improve sleep-disordered breathing in children.
This feedback loop — where structural underdevelopment worsens function, and impaired function worsens structure — underscores the importance of early recognition and intervention during the years of active growth.
Functional Matrix and Oral Posture
Melvin Moss's Functional Matrix Theory (1969) proposed that bone does not grow on its own — it grows in response to the functional demands of the soft tissues surrounding it. The muscles of mastication, the tongue, the lips, the airway, and postural habits all constitute the "functional matrix" that shapes craniofacial skeletal form.
Diet & Chewing
Softer modern diets reduce masticatory loading, diminishing the functional stimulus for jaw development.
Breathing Mode
Chronic mouth breathing alters tongue posture, head position, and mandibular rotation — promoting vertical growth.
Tongue & Posture
Low tongue posture and forward head posture alter the soft-tissue environment, promoting narrow arches and downward growth.
These functional and environmental factors do not replace genetics — they interact with genetic potential. A child with a genetic tendency toward a particular growth pattern may express that pattern very differently depending on diet, breathing, and oral habits during the critical years of facial development.
What Research Suggests About Modern Underdevelopment
The Airway & Facial Growth Philosophy highlights vertical excess of the maxilla and midface as a central, underappreciated problem in modern craniofacial development. When the maxilla grows disproportionately downward rather than forward, a cascade of structural consequences follows — affecting the mandible, airway, bite, and facial balance.
Anthropological evidence from Corruccini, Lieberman, and others demonstrates that modern jaw underdevelopment is not primarily genetic but largely environmental. The transition to softer diets, increased mouth breathing, and altered functional habits has produced a measurable shift in craniofacial form within just a few generations.
Understanding these patterns is essential because it means that growth-centered interventions — aimed at redirecting growth, supporting airway, and restoring functional balance — may be able to address the root cause rather than only managing symptoms.