Anatomy and Physiology of the Temporomandibular Joint

A close up view of the joint

Basic mandibular movements

The basic condylar movements are:

• Rotation in the lower compartment between the

head of the condyle and the disk (without changing the position)

• Translation in the upper compartment between the

head and the condyle as one unit and the glenoid fossa

Terminal hinge axis

Axis of rotation (tansverse, sagital ,vertical )

Terminal hinge axis• It is an imaginary line between the mandibular

condyle around which the condyle rotate during the early openning and late closing (centric relation)can be located arbitary,or by max face bow)

They are usually classified according to the main direction of movement.

The starting position is the habitual intercuspal position, from this point the mandible can move into:

Possible Mandibular Movements

Lateral Movement Opening and Closing Movement

Forward & Backward Movement

Opening and closing movement• the opening movement is carried on by 2 types of

movements:

• a) A hinge (rotary) movement between the heads of the condyles and the discs.

• b) A gliding (sliding) movement between the discs

and the condylar heads moving as one unit on the articular eminence.

• N.B IN FIRST 4 TO 8 MM IS PURE ROTATION WHILE IN FURTHER OPENNING ROTATION AND TRANSLATION

Protrusion and Retrusion The mandible is carried horizontally forward as in

moving the lower anterior teeth in front of the upper. This movement takes place principally in the upper joint.

CONDYLE MOVE DOWNWARD AND FORWARD

Edge to edge position.

Lateral movement In this movement one condyle ( working)

mainly rotates, while the other condyle ( balancing) moves mainly downwards, forwards and medially.

The mandible is capable to move as one unit from one side to the other. This bodily shift is called Bennett Movement

Bennett MovementWORKING

BALANCING

The inclination of the condylar pathTypes :A- Sagittal condylar path angle

B- Lateral condylar path angle

Condylar Guidance .

Lateral Condylar Guidance .

It is the path traveled by the incisal point during the forward glide of the mandible from the intercuspal position towards the maximum forward positionon.

Incisal Path

It is the angle of inclination of a line extending through the incisal edge of upper and lower anterior teeth, to the horizontal plane.

Incisal Angle

The Incisal Path .

The Incisal Path Angle .Vertical Overlap (overbite)Horizontal overlap The greater the amount of vertical overlapThe greater the incisal angle The greater the amount of horizontal overlapThe lesser the incisal angle

Incisal Guidance .

Envelope of motion

• Posselt s figure

No Translation

Translation

Border Positions of the Mandible

These are positions within the boundaries of border positions.

The intra-border Positions