mechanics of mandibular movement
TRANSCRIPT
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
Thank you