during mandibular elevation:-
elastic characters of superior retrodiscal lamina applies a posterior distracture force on the disc.
-superiors portion of lateral pterygoid demonstrates activity ie,,assumed to eccentrically control the posterior point of disc while maintain the disc in an anterior position until madibular condyle completes posterior rotation to normal resting position.
mandibular protrusion and retrusion occur in upper TMJ .
-during protrusion condyle disc complex translates in an anteroinferior direction ,following downward slope of anterior eminence,returns along posterior superior path.
-rotation is not present.
protrussion is an important component necessary for maximal mandibular depression
retraction is an important component of mandibular elevation from a maximally depressed mandible
control of disc during mandibular protrution and retraction:-
-during protraction posterior attachments of disc stretch allow completion of motion
degree of retrusion-limited by tension in TMligament and compression of soft tissue in retrodiscal area between condyle and posterior glenoid spine.
-3mm of translation occur during retrusion
mandibular lateral excursion.:-
moving mandible left and right.
normal degree. 8-11mm
normal motion estimated by observing whether mandible can move full width of one of the central incision in each direction.
-acute lateral excursion is described as contralateral or ipsi lateral relative to the primary muscle action.
lateral excursion
-ipsilateral mandibular condyle spins around verticle axis within the mandibular fossa.
contra lateral mandibular condyle translates anteriorly along the articular eminence.slight degree of spin and lateral glide of contralateral mandibular condyle-(necessary to achieve maximal lateral excursion.
asymmetrical movement of TMJ:-
rotating -one condyle around anterior posterior axis other condyle -depresses-
this movement result in frontal plane motion of mandible with this moving downward and deviating from the miidline toward the condyle ie, spinning.
-combined in to one complex motion using chewing grinding food.
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