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| The inferior LP is highly active during a resisted protrusion
of the
mandible. The resistance is provided the the occluding of the
anterior
teeth, made possible by the elevation of the mandible by the anterior
fibers
of the temporalis.
Since the clenching is done largely on the anterior teeth (thereby limiting temporalis contraction potential) and in a protruded manner (further limiting the temporalis intensity), temporal headache is less commonly reported. As the LPs advance the condyles, the condyles are braced in an
anterior
direction against the eminence (rather than strained medially as in the
excursive movement). The digastric
works in concert with the ILP, aiding in depression the mandible
following the occluding of the teeth. Prolonged protrusive
clenching activities are
therefore well tolerated by the joint complex, but can be straining on
the pterygoid plates of the sphenoid bone (the origin of the LPs,
circled,
below), causing signs and symptoms of "sinus disease" (pain, pressure
of
sinuses). |
An obligatory reaction of the trapezius during a
protursive The utilization of an NTI device eliminates the
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| In the animation to the right,
the left lateral pterygoid (LP) is pulling in two directions: "forward"
anterior/medial on the condyle, and distal/lateral on the
pterygoid plate of the sphenoid bone. The intensity of the
strain on the pterygoid plate is a function of the intensity of the
contraction of the LP. The intensity of the contraction of the LP
is a function of the resistance it encounters durings its contraction
(there is typically none, since LPs serve to disclude the teeth and
open the jaw). The resistance the LP encounters is a function of
the clenching intensity that is maintaining the occluding of the teeth
(in the example, the molars on the right) |
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If the slope of the occluding
surface of
the DE allows for increasing vertical opening upon
protrusion, strain and compaction may persist at the
joints.
 
If the DE's
slope continues
to open the vertical as protrusion procedes beyond the opposing
incisors
(above left), the ramp must be altered to be parallel with the
maxillary
plane (above right)
Clinically, for the symptomatic patient, have
them protrude
as far as possible on the DE and clench. If they report acute and
enhanced pain, reduce the DE as shown and have the patient repeat the
protrusion.
Typically, the pain with be reduced or prevented. Repeat as
indicated. |
 The properly made NTI
device's Discluding
Element creates minimal freeway space and is parallel to the
maxillary
occlusal plane.Although the DE may be
sloped on the palatal side of the incisors to close the vertical
as much as possible, the slope must return to parallel to the maxillary
plane as it extends labially past the upper incisors.
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| If chronic clenching initated at an early age in a protrusive
position,
the utilization of an NTI device will allow the condyles to be seated
to
their optimal orientation, which may be posterior and superior to the
habitual
postion.
The result may be a degree of anterior open bite, in the presense of resolution of symptoms. See also: Informed Consent Reminder.
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