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| Although Lateral Pterygoids are intended to work together to
depress
the mandible, a voluntary unilateral activity results in an excursive
movement
to the contralateral side.
In the example to the right, the contraction of the left
inferior belly
of the LP advances/translates its condyle and then pulls it still
further
medially. Following the cessation of its contraction, the
reciprocal
activity of the temporalis' then elevate the mandible (the superior
belly
of the LP contracts simultaneously with the temporalis, thought to
thereby
stabilize the disc assembly).
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 Practitioners may
be familiar with the effect of a unilateral LP contraction following a
PSA anesthetic block. The ipsilateral LP may be anesthetized and
not able to advance its condyle. The opposite side LP pulls its
condyle anterio-medially, while the anesthetized side opens very
little, as demonstrated in the graphic above right.
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 An imbalance of
opening efforts can be seen in the garage door
example above. The absence of the left spring prevents the door from opening fully on the left side. In the jaw example above, absence of right LP contraction results in a left excursive movement. Deviations upon opening are most likely due to differences in tension of the two lateral pterygoids. |
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