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Rotational movement

Usually the first half inch (16mm) of opening
Rotational center is at the condyle

Translational movement

Second part of opening
Movement down the articular eminence
Rotational center moves to the angle of the mandible
Arc of movement more acute than in rotational

The three basic axes about which mandibular movement rotates

Transverse
Vertical
Sagittal

CR Position

Condyles are in a most retruded physiologic position
Condyles assume a superior position against the articular disk and the stress bearing surface of the articular eminence

Maximum intercuspation

Stamp cusps of the max posterior teeth occlude in the fossae and/or on the marginal ridges of the mand teeth
Stamp cusps of the mand posterior teeth occlude in the fossae and/or on the marginal ridges of the max teeth

The anatomical determinants of occlusion

Detrusion
Transtrusion
Vertical laterotrusion
Horizontal laterotrusion

Trusion

to thrust

Trans

Across; on the other side; beyond

Transtrusion

Movement of the condyles in the horizontal plane. It includes laterotrusion and mediotrusion

Laterotrusion

movement of the working condyle away from the midline

Mediotrusion

movement of the nonworking condyle towards the midline

Pure lateral movement of condyle

Latero-trusion

Upward movement of the condyle

Sur-trusion

Downward movement of the condyle

De-trusion

Forward movement of the condyle

Pro-trusion

Backward movement of the condyle

Re-trusion

The path of the mandibular condyles can be studied through the recording of mandibular movement with a

Pantographic tracing device

The amount of detrusion determines..

.. how long the cusps can be and how deep the fossae can be
Also affects the amount of concavity of the anterior teeth

More detrusion

May have longer cusps and deeper fossae

May have less concavity

Less detrusion

MUST HAVE shorter cusps and shallower fossae

MUST have greater concavity

An increase in laterotrusion requires...

... the ridge and groove direction of the mandibular posterior teeth to be more mesial and on the maxillary teeth to be more distal

Shorters cusps for all posterior teeth (to avoid interference)

Greater concavity of max cuspid lingual surface

Latero-sur-trusion

If the W.C. moves up
Cusps MUST be shorter
Fossae MUST be shallower
Lingual concavity of the anterior teeth MUST be greater

Latero-de-trusion

If the W.C. moves down
Cusps MAY be longer
Fossae MAY be deeper
Lingual concavity of the anterior teeth MAY be less

Lateroprotrusion

W.C. moves forward as it moves laterally
Mandibular grooves more Distal
Maxillary grooves more Mesial
Concavity must be greater

Lateroretrusion

W.C. moves backward as it moves laterally
Mandibular grooves more Mesial
Maxillary grooves more Distal

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