MANDIBULAR MOVEMENTS

TYPES OF MOVEMENTS OCCUR IN THE TMJ :

Rotation

Translation

Rotational movement

the inferior cavity of the joint

Horizontal axis of rotation (hinge movement) :

Vertical (frontal) axis of rotation:

Sagittal axis of rotation:

TRANSLATIONAL MOVEMENT

the superior cavity of joint

Single-plane Border

Movements

SAGITTAL PLANE

1- Posterior opening border.

2- Anterior opening border.

3- superior contact border.

4- Functional movement.

Limiting factors :

posterior opening Ligaments Anterior opening Morphology of TMJ

Superior contact Surfaces of the teeth.

Functional movement Neuromuscular system

1.Posterior opening border movement :

• stage 1 : pure rotational movement . first 20-25 mm .

• stage 2 : • translation• rotation

2. Anterior opening border :

• Contraction of inferior lateral pterygoid.

• from max open to max protrusive position.

• not pure hinge movement

Relationship of the teeth when the condyles are in the CR.

3.Superior contact border movement:

superoanterior shift to ICP

Muscular force is applied to the mandible

As the mandibe moves forward

inferior movement result

the incisal edges of max & mand teeth pass across each other

Horizontal movement of the mandible

Superior movement.

anterior teeth pass beyond edge to edge position.

posterior teeth contacts.

Horizontal movement

determined by the posterior teeth surfaces

until the maximum protrusive movement

• 90% of population• 1 – 1.25 mm• No superior slide to

ICP

4.Functional movement :

during activity of the mandible

free movement

begin at/ below ICP

Postural position 2- 4 mm below ICP

Chewing stroke

HORIZONTAL PLANE

Gothic arch tracer

A rhomboid shaped pattern

Has four distinct movement components

left lateral border movements :

• Left condyle: rotating/ working condyle

• Right condyle: orbiting condyle/ non-working condyle

2. Continued left lateral border movement with protrusive:

Contraction of left inferior lateral ptrygoid + continued contraction of right inferior ptrygoid:

1. left condyle move anteriorly and to right.2. Mandibular midline back to coincide with the midline of the face.

Right lateral border movement:

• Right condyle: rotating/ working condyle

• Left condyle: orbiting condyle/ non-working condyle

4. Continued right lateral border movements:

contraction of right inferior pterygoid muscle +continued contraction of left inferior pterygoid:

1. right condyle move anteriorly and to left.2. Mandibular midline back to coincide with the midline of the

face.

Functional movement :

occur near ICP.

During chewing the range of jaw movement begins some distance from maximum ICP. But as food is broken down into smaller particle size, jaw action moves closer and closer to ICP.

FRONTAL (VERTICAL) BORDER & FUNCTIONAL MOVEMENT

shield shaped pattern

1. Left lateral superior border2. Left lateral opening border3. Right lateral superior border4. Right lateral opening border.

Left lateral superior border movement:

When mandbile is in maximum intercuspation Inferiorly concave path

Left lateral opening border movement:

When maxmium opnenig is approached Lateraly convex path. Mandibular midline to coincide with midline of the face.

Right lateral superior border movement :

Mandible is returned to maximum intercuspation Inferiorly concave path

Right lateral opening border movement :

When maxmium opnenig is approached Lateraly convex path. Mandibular midline to coincide with

midline of the face.

Functional movement It begins and ends at ICP. During chewing 1. the mandible drops directly inferiorly until desired opening

is achieved. 2. It then shifts to the side on which the bolus is placed and

rises up. 3. As it approaches maximum intercuspation, the bolus is

broken down between the opposing teeth. 4. In the final millimeter of closure, the mandible quickly shifts

back to ICP.

ENVELOPE OF MOTION

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