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AN ORAL MOTOR PERSPECTIVE ON BRUXISM (tooth grinding)
Bruxism, or tooth grinding, may occur for a variety of reasons, some of which include
poor temporal mandibular joint formation or alignment, ear infection, gum infection,
tooth disease, tooth eruption, sinus infection, pain any where in the body, muscle
weakness or abnormally increased muscle tone. The focus of this article is bruxism
due to muscle weakness or abnormally increased muscle tone.
Consider the muscle sling
which supports the alignment and movement of the lower jaw. It is made up of muscles
in the posterior cheeks, the muscles of the tongue, the soft palate, and muscles
on the side of the head. (if needed, an illustration of these muscle areas could
be included) In a twenty-four hour period, the teeth actually touch an average of
less than ten minutes, the time the teeth come into contact during chewing, excluding
recreational chewing on gum. The majority of the day and night, the lower jaw is
held in a position approximating closed, usually less than 1/4 inch apart from the
teeth of the upper jaw. To maintain this position, the muscles supporting the jaw
must be strong enough to withstand the constant force of gravity, pulling the jaw
down. If the muscles are weak, as is the case with both low tone and high tone muscles,
there are fewer options for jaw alignment and movement. There are two options: opened,
or closed. As soon as the upper teeth come into direct contact with the lower teeth,
a reflexive response of subtle shifting across the dental surfaces occurs, resulting
in bruxism.
To determine the muscle areas involved, a baseline of the components
of muscle movement must be determined. These components include: response to pressure
and movement, range of movement, variety of movement, strength of movement, and control
of movement. The areas assessed include the lips, cheeks, jaw and tongue. Observation
of the face at rest, and during activities such as eating, drinking, talking, and
during change in facial expression are important. The structures of the face and
mouth should be inspected visually for alignment and symmetry. In addition to observation,
the lips, cheeks, tongue and jaw can be manipulated manually, using the Beckman Oral
Motor protocol, to add data regarding the components of movement listed above. This
is especially important if the individual is nonverbal, on nonoral intake, or cannot
follow commands. Findings from this baseline will yield data critical to the design
of an effective intervention program.
Interventions dependent on the individual maintaining
conscious control of the bruxism usually result in limited success. The small reflexive
muscular adjustments necessary to maintain the jaw in alignment and approximating
closed are not mediated cognitively. That means that if each of us had to constantly
be aware of and adjust the alignment of the lower jaw, we would have our conscious
brain circuitry so tied up, it would be difficult for us to accomplish any other
task during waking hours, and it would be impossible to do when asleep. Internal
jaw stability is the key to functional movement and alignment of the lower jaw. Also
note that although squeezing the outer face may result in brief cessation of the
bruxism, often due to the sensation of pain, that cessation can not be internalized
until the muscles responsible for the task have adequate strength to do the job.
Interventions which provide opportunity for active muscle contraction against resistance
have resulted in increased strength for the muscles of the jaw, cheek, intrinsic
tongue muscles and soft palate with a significant decrease in bruxism for many individuals
with low muscle tone. For some individuals, the bruxism may still occur, especially
during times of physical stress, illness, or change in motor skills - either gross
motor or fine motor. The overall incidence is reduced to a level that allows for
a variety of jaw movements through out the day, with better jaw alignment at night.
Additional interventions may be necessary, such as night splints for the mouth. The
focus of the oral motor interventions is to maximize jaw function in balance with
the other structures and muscles of the face.