The most intense contraction of the temporalis
is with the jaw slightly open, and (of course) when there is resistance
to its effort (left) as with a full coverage splint.. The occluded
teeth on the splint provide considerable resistance to the lateral pterygoid's
efforts at contraction (as they try to re-open the mandible). Therefore,
the LPs may not have an adequate opportunity to relax and become normal,
thereby maintaining the anterior-posterior orientation of the condyle.
Additionally, the presense of the splint prevents any vertical seating
of the condyle(s).
By providing an anterior midline point stop
(like an NTI, or PankeyJig/Best-Bite/Lucia jig), the resistance to both
the elevating muscular and to the LPs is decreased or eliminated (right,
above)
If for example, the condyle(s) were functioning
in a position slightly anterior and inferior to the optimal musculoskeletally
stable position (left), without the resistance of the occluded teeth, the
LP may lengthen (arrow within LP in left diagram) as the elevating musculature
positions the condyle(s) more superiorly while the lengtheing LPs allow
re-positioning posteriorly. Ultimately, "the functional pull of the
major elevator muscles will seat the condyles in their most superioranterior
position in the fossae resting against theh posterior slopes of the articular
eminences"*
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