The Role of the Airway
The face and neck grow around the airway, and their growth determines mandibular and head posture, therefore considering airway dynamics in treatment planning is critical to success in TMJ, orthodontic, and postural treatment.
THE PROBLEM - During evolution, the teeth were the fragile components of our jaw systems, so protecting them became a high priority for our neuromuscular systems. As a result, your jaw muscles are programmed to protect your teeth by only allowing you to close your mandible (lower jawbone) in the one central bite location where all your back teeth fit together and making that position feelnormal, wherever it is. Also, your jaw muscles hold your mandible in a postural location just beneath that central bite location in order to maintain fast easy access to mandibular bracing, because that access was critical in evolution in order to protect the vital structures behind the mandible, so that also feels normal. As a result, the bite controls mandibular posture.
However, an even higher priority for the neuromuscular system is to protect the airway passage. If the bite forces mandibular posture into the area needed for airway passage, the body will use the tongue, jaw, and neck muscles to create a new mandibular resting posture that re-establishes resting airway passage. There are two areas where our airways become restricted and trigger such adaptative muscle responses.
NASAL AIRWAYS usually become obstructed due to insufficient expansion of the midface. The palate, in the center of the midface, forms the roof of the mouth and the floor of the nose. When the upper jawbone cannot fully unfold and the palate remains narrow, the base of the triangular nasal cavity remains narrow. It may be to narrow to allow sufficient airway passage at rest. The body's response is then to create and maintain an oral airway passage, keeping the lips always slightly parted.
Mouth breathing then causes serious problems. It prevents the nose from warming, filtering, and moistening the air that strikes the back of the throat. It prevents nitric oxide from getting to the lungs. It leads to poor upper respiratory health. Mouth breathing can usually be corrected in adults by wearing a palate expansion appliance for 3 to 6 months, as explained in the file entitled PALATE EXPANSION.
If the nasal airway passage is obstructed by structures within the nasal cavity, such as overgrown turbinates or a deviated septum, the internal nasal cavity will need to be reshaped. This can be accomplished surgically, but it is difficult. Alternatively, it may be possible to expand the internal nasal airway by forced nasal breathing, because localized areas of high speed turbulent airflow trigger regressive osseous remodeling that removes obstacles to airflow.
PERSONAL STORY - About 20 years ago, when I first began looking at the relationship between facial growth and airway flow, I realized that animals always nose breathe, even when running for their lives. They only mouth breathe to gasp, when fighting. I also realized that, when I went jogging, I could keep my lips sealed and breathe through my nose if I went slow enough. That summer I went jogging twice a week, always nose breathing and limiting my pace to what my nasal airway could accomodate. By the end of that summer, it could accommodate natural jogging. I could run a good natural pace with my lips sealed, and I still do.
SMALL NOSTRILS - In some people, the limit to nasal airway flow is at its entry through the nostrils, and normal nasal airway flow during sleep can sometimes be restored by using simple technologies like nasal cones or nasal strips to enlarge the restricted area.
PHARYNGEAL AIRWAYS - usually become obstructed due to a facial growth pattern in which the mandible keeps shifting backward or rotating down and back into the area needed for airway passage through the pharynx. The mandible is programmed to elongate slowly throughout life so it can continuously advance in order to gradually decrease resistance to airway flow as muscle strength decreases slowly throughout life. However, when a steeply interdigitated bite or a deep overbite prevents the front end of the mandible from advancing, the growth of the mandible gets redirected. It rotates down and back, where it can impinge on the space needed for oropharyngeal airway passage.
The body's adaptation to pharyngeal airway obstruction is to alter the tonus of the nearby muscles to find a resting posture that restores airway flow. Neuromuscular reflexes ensure that all the muscles of the head and neck will automatically acquire whatever resting postures are necessary to keep the airway passage open. The tongue is primarily responsible for maintaining the pharyngeal airway. When the bite forces the mandible back into the pharyngeal airway space, the neuromuscular system may respond by shifting the resting posture of the tongue to a location between the teeth, as evidenced by visible scalloping in the sides of the tongue. When the tongue acquires an adaptive position by resting between the front teeth, it separates those front teeth and produces an anterior open bite that makes it impossible to incise (bite things off). In these cases, any orthodontics that straightens teeth by moving them into the path of the resting tongue posture will fail, because the tongue will eventually reposition the teeth in any way needed to keep the airway passage open.
When the mandibular posture shifts posteriorly, the body adapts by tipping the head back (extension) to pull the mandible up and forward away from the cervical spine to increase the amount of airway space behind the mandible; but the head extension also produces a forward shift of head posture, as described in THE ROLE OF BODY POSTURE under the TMJ DISORDERS tab and in more detail in BITES AND POSTURE under the FOR DOCTORS tab.
The problem of the backwardly rotated or backwardly positioned mandible can be treated preventively by functional orthodontics that encourages mandibular advancement, it can be treated actively by forcing the mandible into an advanced position during sleep, or both. Treatment by functional orthodontics is described in the file entitled THE ROLE OF ORTHODONTICS under the tab TMJ DISORDERS. Active treatments for snoring and sleep apnea are summarized under the tab SLEEP APNEA and described in detail in the file entitled, MULTILEVEL TREATMENT OF SLEEP APNEA under the tab FOR DOCTORS.