Bite Changes in Dentistry

by Michael L. Gelb, DDS, MS

Bite changes have been a most exciting topic in dentistry over the last 20 years.

We now know that our skulls are changing in shape as our brains have enlarged and our diets have softened. According to the research of Lieberman,1 Corrucini,2 Weston Price3 and Nestor,4 our midfaces are retruding due to epigenetic factors. The maxillary and mandibular arches are also shrinking. McNamara found that 82% of maxillas are retruded. Retraction of the mid-face results in airway narrowing, which can lead to sleep-disordered breathing. Narrowing of the maxilla and a heightened narrow palate often results in nasal narrowing and increased nasal resistance. An inability to nose breathe frequently results in mouth breathing, the first sign of an airway issue and sleep-disordered breathing. Inspiratory flow limitation or upper airway resistance can also lead to a sensitized autonomic nervous system and an increase in Functional somatic syndromes, according to Avram Gold.5

Midface retrusion also results in mandibular retrusion, which increases after perimenopause. Mandibular retrusion often results in temporomandibular joint internal derangement and temporomandibular disorders. Mandibular retrusion also retracts the tongue, leading to airway collapse, resistance, and obstruction.

As the jaw relaxes with appliance therapy, the lower jaw often moves forward. Mandibular repositioning appliances, both upper and lower, used day and night can result in bite changes. This usually happens when the upper anterior teeth are torqued lingually or backwards. It frequently occurs when the maxillary or upper teeth are retruded in the skull. Only the anterior teeth meet as the lower jaw assumes the correct and comfortable position. Mandibular advancement devices (MAD) are often prescribed for sleep-related breathing disorders and can result in bite changes.

The question then remains, should the dentist retrude the lower jaw in the morning with an AM aligner? Moving the jaw back could compress the TMJ and narrow the airway. However, moving the jaw back could improve the ability to chew comfortably. Often both goals can be achieved. For example, an AM aligner for 30 seconds can temporarily “improve” the bite to allow easier chewing. Unfortunately, when we say improve, it’s helping tooth alignment but potentially harming the TMJ and Airway.

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Fig. 2A

. After

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Fig. 2C


Tooth Alignment – Don’t close the airway

Focus on tooth alignment at the expense of TMJ and Airway is potentially very damaging. Interproximal reduction with clear aligner therapy can retract the jaws, trapping the lower jaw and exacerbating TMJ and airway disorders.

Nightguards made in a retruded position can do the same thing. As a result, they often close the airway, worsening snoring, sleep apnea and potentially hypoxic burden.

Orthodontics involving headgear, upper or four bicuspid extractions can have the same effect.

Restorative dentistry in a retruded centric-relation position can also have negative consequences.

Any procedure that retracts the upper or lower jaws can harm the airways and jaw joints.

It is no longer acceptable to close the airway! Doing so risks harm and liability.

Fig. 3

. Cone Beam 3D- CT imaging showing a narrowed airway.
Cone Beam 3D- CT imaging showing a narrowed airway.

The dentist can usually tell on the initial exam which patients require orthodontics. In addition, because of their training, general dentists are often better equipped to perform airway orthodontics than traditional orthodontists.

When the patient is informed of the morphology of their skull, jaws and bite due to craniofacial respiratory factors, they begin to understand how their breathing contributed to current symptoms. Again, the CBCT scan illustrates these changes clearly.

Devolution or narrowing of the jaws over the last three centuries has contributed to the epidemic of sleep-disordered breathing and narrowed airways. It is no longer challenging to comprehend that expansion orthodontics can open the nasal and pharyngeal airways and improve sleep physiology, inflammation, brain and cardiovascular health.

Bite changes are often necessary and preferred when the health and wellness of the patient are put above dental occlusion and the dogma of some dentists. AM aligners have gone a long way to keep both sides and patients happy during function.

Oral Health welcomes this original article.


  1. Daniel Lieberman: The Evoluvion of the Human Head, January, 2011.
  2. Robert Corruccini: How Anthropology Informs the Orthodontic Diagnosis of Malocclusion’s Causes,January, 1999
  3. Weston Price: Nutrition and Physical Degeneration, 8th edition, Price Pottinger nutriction foundation, 2009
  4. James Nestor: Breath: The New Science of a Lost Art, May 2020
  5. Functional somatic syndromes, anxiety disorders and the upper airway: a matter of paradigms Avram R Gold, February 2011

About the Author

Dr. Michael Gelb is a world-renowned inventor, lecturer, NYU professor & author of the best-selling book GASP: Airway Health – The Hidden Path to Wellness. Known for his breakthrough work in TMJ, airway centered disorders, sleep apnea, sleep disorders, and chronic headache treatments, Dr. Gelb has pioneered and coined Airway Centric® dentistry and is transforming lives at scale by helping people feel and breathe better. A board member and chair of the Development Committee for the Airway Revolution Foundation and a co-founder of The Foundation for Airway Health, The American Academy of Physiological Medicine and Dentistry and The Gelb Institute.