Lecture 6 - Mechanics of Mandibular Movement Flashcards
what are the four anatomic determinants of movement
-right TMJ
- left TMJ
- teeth/occlusion
-neuromusculature
where does rotational movement occur
in the inferior joint compartment
where does translational movement occur
in the superior joint compartment
when does rotation occur
when the mouth opens and closes around a fixed point or axis within the condyles
where does the condyle rotate in rotation
on the inferior aspect of the articular disk
when does rotation vs translation occur
rotation occurs for the first 20-25 mm of opening then further opening translation occurs
what 3 reference planes may rotational movement occur in the mandible
-rotation in the sagittal plane around a horizontal axis
- rotation in the horizontal plane around a vertical axis
- rotation in the frontal plane around a sagittal axis
what is the horizontal axis that passes through both R and L condyles called
-terminal hinge axis
- transverse hinge axis
- horizontal hinge axis
What is the only rotational movement that can be isolated clinically and recorded and identifiable
rotation in the sagittal plane around a horizontal axis
when does rotation in the horizontal plane around a frontal axis occur
during lateral movement
where is the frontal axis located in rotation in the horizontal plane around a frontal axis
in the working side condyle
where does the non-working side condyle move in rotation in the horizontal plane around a frontal axis
medially and forward in the horizontal plane orbiting around this frontal axis
when does rotation in the vertical plane around a sagittal center of rotation occur
during lateral movement
where is the sagittal axis located in rotation in the vertical plane around a sagittal center of rotation
working side condyle
where does the non-working side condyle move in in the vertical plane around a sagittal center of rotation
inferiorly in the frontal plane around the sagittal axis
what is the point called where are three axes (horizontal, vertical, and sagittal) meet
the rotational center of the condyle
what is translation defined as
every point in an object (mandible) simultaneously moving in the same direction with the same velocity
when does translation occur
depression of the mandible beyond 25 mm, and in protrusion
what do the working side condyle and non working side condyle do in lateral translational movement
working side: move downwards, forwards, and medially
non-working side: may shift laterally, called the Bennett movement
what is the working side of the mandible in lateral movement and the non working side and what are the both called
-working side: the condyle on the side towards which the mandible moves- called the rotating condyle
- non- working side: condyle on the side opposite to which the mandible moves - called the orbiting condyle
what do the working side and non working side do in lateral movement
-working side: condyle rotates around a vertical axis
- non-working side: condyle moves downwards, forwards, and medially through a series of rotations
what is the condylar angle defined as
angle at which the condyle moves away from a horizontal reference plane
how can the condylar angle be recorded on a patient
via a protrusive movement or via lateral movements
what is the condylar angle influenced by in protrusive movement
the posterior slope of the articular eminence
is the angle of the posterior slope of the articular eminence the same in everyone
no
what is the condylar angle measured via lateral movement influenced by
the steepness of the medial wall of the articular fossa - non-working side
is the condylar angle slightly steeper when recorded in protrusion or lateral movement
lateral movement
what is fischers angle defined as
the angle formed by the intersection of the protrusive and non-working condylar paths as viewed in the sagittal plane
what is fischers angle the difference between
the condylar angle recorded with a protrusive and lateral record
medial wall of the articular fossa is generally steeper than ____
the posterior slope of the articular eminence
what is fischers angle usually
5-10 degrees
what is bennett angle
the angle at which the NWS condyle moves medially away from a sagittal reference plane as viewed in the horizontal place during a lateral movement
what is bennett movement
bodily movement of the mandible during lateral excursive movement
what happens in bennett movement
the working side condyle rotates and also shifts laterally during the lateral movement, this lateral movement of the working side condyle is the bennet movement
what happens in protrusion
-both condyles translate
- condyles move forwards and downwards
- condyles move down the posterior slope of the articular eminence (condylar guidance angle can be calculated from this)
