Mechanisms of Mandibular Movement Flashcards
What are the 4 anatomic determinants of movement?
Right TMJ
Left TMJ
Teeth/Occlusion
Neuromuscular
Which axis of the mandible is the most basic fundamental?
Hinge Axis
___ is the imaginary line drawn between the 2 condyles where the mandible will open and close about this axis
Hinge Axis
_____ is the movement of the mandible forward until front teeth come into contact
Protrusion
What muscles are involved in protrusion?
lateral pterygoid; assisted by medial pterygoid
What muscles are involved in retraction?
Posterior fibers of temporalis, deep masseter, and geniohyoid and digastric
What muscles are involved in elevation?
Temporalis, masseter, and medial pterygoid
What muscles are involved in depression?
digastric, geniohyoid, and mylohyoid muscles
What are the 2 movements of lateral movements of mandible?
Rotation and translation
Which condyle rotates in lateral movement?
Working condyle (side toward which the mandible is moving
Which condyle translates in lateral movement?
Non-working/ Balancing condyle
T/F: Many of the terms and words of occlusion originated with the construction of denture
True
____ occurs when condyles move down articular eminence
Translation
_____ occurs for the first 20-25mm of opening
Rotation
Only _____ movement can be isolated clinically
rotational movement
_____ movements may occur in all three reference planes in the mandible
Rotational movements
What are the 3 planes rotation can occur?
Sagittal, frontal, and horizontal
_____ in the vertical plane around a sagittal center of rotation Occurs during lateral movement Sagittal axis is in the working side condyle; Non-working side moves inferiorly in the frontal plane around sagittal axis
Rotation
____ in the horizontal plane around a frontal (vertical)axis; Frontal axis is in the working side Occurs during lateral movement; non working moves medially and forward in the horizontal plane around this frontal axis
Rotation
Where all three axes (horizontal,vertical and sagittal) meet is called the ______
rotational center of the condyle
To do a protrusive movement, both _____ contract to move mandible forward
Lateral pterygoids
What muscle functions in translation?
Lateral pterygoids
In what movement do Both condyles translate; Condyles move forwards and downwards; Condyles move down the posterior slope of the articular eminence
Protrusive movement
The ______ is the only joint in the body capable of moving in three dimensions.
temporomandibular joint
When a condyle moves in a _______, it goes over the medial wall of the glenoid fossa
Lateral translation
During, the angle is influenced by the ______ of the articular eminence.
posterior slope
The condylar angle measured via lateral movement is influenced by the ______ of the articular fossa (non-workingside)
steepness of the medial wall
once the condyle begins to move in any direction, it is no longer ______, it will begin to move either forward or laterally in the fossa.
rotating
An immediate lateral shift of the working condyle is called
Immediate side shift
A slower lateral shift of the working condyle is called
Progressive side shift
During a lateral movement, this is the condyle on the side towards which the mandible moves–A.k.a. rotating condyle
Working side condyle
This is the condyle on the side opposite to which the mandible moves–A.k.a. orbiting condyle
Non-working side condyle
_____ condyle moves downwards, forwards and medially Moves over the steeper medial wall of the articular fossa; Can record the condylar angle from this movement also; Condylar angle is usually slightly steeper than when recorded in protrusion
Non-working side condyle
_____ condyle mainly rotates around a vertical axis (it does not move out of the articular fossa)
Working side condyle
Sometimes the orbitingside condyle does not simply rotate but also shifts laterally during the lateral movement.This lateral movement of the orbiting side condyle is called the _______
Bennett movement.
Bodily shift of the mandible toward the working side during lateral excursion
Bennet’s movement
The _____ the teeth are to the working condyle, the shorter will be the cusp height
closer
______ is the angle formed by the sagittal plane and the path of the advancing orbiting condyle during lateral mandibular movement as viewed in the horizontal plane.
Bennett angle:
Angle at which the condyle moves away from a horizontal reference plane; can be recorded (estimated) on a patient; Can be recorded via a protrusive movement or via lateral movements
Condylar angle
What is the plane of reference for the condylar angle?
Frankfort’s horizontal plane
_____ is The angle formed by the intersection of the protrusive and non-working condylar paths as viewed in the sagittal plane.
Fischer’s angle
The difference between the condylar angle recorded with a protrusive and lateral record; Medial wall of articular fossa is generally steeper than the posterior slope of the articular eminence (5-10°0
Fischer’s angle
The dynamic relationship of the lower anterior teeth against the upper anterior teeth through all ranges of function
Anterior guidance
What are the only 2 teeth you want touching during lateral protrusive?
Canines
What are the teeth you want touching during protrusive movements?
Incisors
_______ protect the posterior teeth in all mandibular excursions
Anterior teeth
____ protect anterior teeth by taking the force of closure of the mandible
Posterior teeth
Class ___ lever will create the least stress to the anterior teeth
Class 3
The closer to the fulcrum a tooth is, the ____ force it will have
More force
If a posterior nonworking contact occurs during the protrusive biting function, the fulcrum point moves from the temporomandibular joint to the point of faulty contact, forming the Class ____ lever
Class 1 lever
The premature nonworking contact (B) triggers a more forceful closure of the muscles (P) on the nonworking side. This changes the normal Class III lever system to the destructive Class ____ lever system and puts an unusual amount of stress on the undesired contact.
Class 2 lever
The amount of _____ that can be generated between the teeth depends on the distance from the temporomandibular joint and the muscle force vectors. Much more force can be generated on the posterior teeth, than on the anterior teeth.
force
