Pacific Coast Society of Orthodontists Bulletin Spring 2023 - 53

Presentation Summary
Doctors
The Mystery of the Anterior Open
Bite-Is It Really the Teeth?
Dr. Dania Tamimi presented " The Mystery of the
Anterior Open Bite " at a seminar presented by the
California Association of Orthodontists in Sacramento,
California, on March 10, 2023.
Dr. Dania Tamimi
Orlando, FL
PCSO Bulletin Contributor
Dr. Tamimi is an oral and maxillofacial radiologist
with a private practice in Orlando, Florida. She has a
passion to help dentists and physicians understand
the temporomandibular joint (TMJ) biomechanically
and psychosocially and its relevance to dental
treatment. She lectures nationally and internationally
on the topic of understanding the TMJ and the
airway and the use of radiographic imaging for
orthodontics. She is the author of several textbooks,
most recently, Specialty Imaging: Temporomandibular
Joint and Sleep-Disordered Breathing.
One of the vexing issues that may arise in the
orthodontic practice is the relapse or change of the
bite a few months or years after the completion
of treatment. While it is tempting to consider a
dentoalveolar etiology, the reality is many of these
bite changes have etiologies that lie outside the
dentoalveolar complex. A complete and thorough
clinical and radiographic evaluation is necessary
with initial records to rule out the presence of any
of the culprits that may lead to a bite change, with
the understanding that many of the usual suspects
(such as the TMJ and airway) may be overlooked
at the initial treatment-planning phase. Diagnosis
of the patient, not just the occlusion/malocclusion,
is key to the long-term success and stability of the
orthodontic treatment.
There are many etiologies and presentations for
bite changes, but the most commonly overlooked
ones are the TMJ and upper respiratory tract
obstruction. As space is limited in this journal,
this article will tackle the anterior open bite that
results from degenerative joint disease (DJD) and
airway narrowing, with the understanding that
the differential diagnosis list for bite changes in
general and anterior open bites in particular is long
and extensive. The understanding of the role of
DJD and compromised airway patency allows us to
understand the craniofacial complex as a system of
multiple connected and communicating parts that
are interrelated. This understanding translates to
Spring 2023 PCSO Bulletin
many of the conditions that may compromise the
TMJ and airway and can be used as a base to help
widen the clinician's diagnostic scope and clinical
observation acuity.
While an anterior open bite can have a mechanical
etiology (digit sucking or tongue thrusting,
for example) or could be due to an ankylosed or
submerged tooth, the TMJ and the airway should not
be overlooked when trying to identify the reason behind
an open bite. A tongue thrust habit may be an
attempt to increase airway dimensions in a narrowed
oropharyngeal tract as can a mandibular autoadvancement
habit. The TMJ and upper respiratory
tract are structures that are physiologically, developmentally
and functionally intertwined, and often a
dysfunction in one can lead to a dysfunction of the
other. They are similarly linked to the occlusion, and
changes in the structure and position of the condyles
as well as dimensions and patency of the airway can
affect the occlusion. A deep dive into the anatomy
and linkages between the mandible, skull base, and
cervical spine can further aid in understanding this
relationship but is not within the scope of this article.
When it comes to the TMJ/airway etiology of the
anterior open bite, the dilemma can be a " chicken
or the egg " quandary: did the TMJ dysfunction
precipitate the airway narrowing, or did the airway
narrowing cause a cascade of events that led to the
TMJ dysfunction?
Let's start with the first scenario of the TMJ dysfunction
causing the airway narrowing, which is the
scenario most widely accepted in dentistry. If there
is bilateral condylar height and volume loss, such
as can occur with DJD (idiopathic condylar resorption
[ICR] or adult DJD), or inflammatory arthritis
(juvenile idiopathic arthritis [JIA] or rheumatoid
arthritis), that reduction of condylar volume leaves
behind a space in the glenoid fossa, creating an
orthopedically unstable joint (Figures 1 and 2). This
space creates a potential for the superior repositioning
of the condyles, which will then rotate the
mandible posteriorly around a last molar tooth
fulcrum, resulting in an anterior open bite (Figures
3 and 4). Due to the attachment of the tongue and
floor of the mouth muscles to the mandible, these
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Pacific Coast Society of Orthodontists Bulletin Spring 2023

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