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25 terms

Mandibular Movement

STUDY
PLAY
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