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How "Canine Rise" serves to diffuse parafunction |
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| When either or both temporalis' contract during the normal unilateral activity of a Lateral Pterygoid muscle, the LP encounters a degree of resistance to its effort, and that resistance is the occluding of the teeth. The resulting direction of the force vector of this effort is a fucntion of the point of resistance. Since the temporalis persists in the elevation of the mandible, the canine teeth contralateral to the translating condyle are often exploited to endure the load, thereby allowing the force to be directed in an anterior (and slightly medial) direction, braced by the slope of the eminence.
This is called "canine rise, or guidance", allowing the posterior teeth to separate.
In the example below, the right temporalis persists in its elevation of the mandible, thereby providing prolonged occluding of the right side canine.
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| Although the lateral engagement of the canines can help to diffuse the effects of parafunction, an end-to-end canine contact can serve to perpetuate the symptoms of parafunction.
The animation to the right demonstrates a parafunctional excursive movement that allows for canine-to-canine clenching. Although elevating intentisty is reduced during the opening stroke, it intensifies when the canine teeth are end-to-end. (Canine teeth can allow for near maximal voluntary temporalis clenching intensity.) The re-closing stroke is what creates the wear facets typically observed on incisors.
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The misnomer of "Outside-in" chewing.
Normal opening is straight, unless a chronically-tensed/fatigued LP advances its condyle "faster" that the contralateral LP.
Canine teeth (nor the incisors) do not contact and rub on each other during mastication.
Excursive parafunction does not engage the canine during closing (ie, from the outside-in).
The above example does not really happen. Interferences are enganged by the LP upon opening (at right).
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The misnomer of : "Inside-out" chewing.
Deviation upon opening is abnormal and is usually the
result of excursive parafunctional opening against resistance. Ideally, this parafunction "grinding" activity would engage a canine, but can still fatigue a lateral pterygoid depending upon the intensity of resistance provided by the occluding canines (a function of the temporalis). Occasionally, canine tip-to-tip clenching perpetuates the clinical presentation of unilateral headache and contralateral joint strain. In actual mastication, the teeth disclude in unison, and not in an excursive grinding movement.
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