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Working posterior interferences = non-working side joint strain during parafunctional occluding |
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| he position of the contact(s) during parafunction dictate the potential degree of resultant joint strain (if any). Whereas in bilateral clenching (no effective condylar translation on either side), there is insignificant (if any) joint strain.
A contralateral, most distal contact contact is made possible by the continuing contraction of the contralateral temporalis. The force generated by the ipsilateral inferior Lateral Pterygoid is directed at the point of resistance, (that being the contralateral contact) which is in a mesial direction (which is the least desirable).
This also demonstrates the irony of "posterior support for the joint". In the adjacent example, the right condyle is stablized and minimally strained due to the posterior contact on its side, which is only made possible by a parafunctional contraction of the right temporalis. If not for that activity, there would be no need for "posterior support".
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Some texts on occlusion refer to the "spasming of the LP
due to the existance of a posterior interference". A true
spasming of an LP would cause the manible to fly open.
However, with the persistance of temporalis contraction,
the contraction of the LP is greater than normal, thus
making it appear to "spasm".
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  The more resistance there is to elevating the mandible (or arm), the more intense the effort must be. The significant difference between the opening of a garage door and the opening of the mandible, is that garage doors springs do not have gravity working with them. Once one side has been stabilized, the attempt at opening the other side can be straining to the joint. |
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