tmj pptx - د.رضوان

Tmj anatomy ,physiology, mandibular movements

Lec. 1
By
Assis.Prof.Radhwan Himmadi Hasan
B.D.S , M.Sc. , Ph.D. Prosthodontics
Assis.Prof.Radhwan Himmadi Hasan
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Assis.Prof.Radhwan Himmadi Hasan

Envelope of Motion

Dr ulf posselt’s in 1952 first described a 3D concept of mandibular movements
It was a Combination of border movements in all 3 planes:
a) Sagittal
b) Horizontal
c) Frontal
The envelope differs from person to
person but it has the same
characteristic shape
Assis.Prof.Radhwan Himmadi Hasan
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Envelope of Motion

The superior surface of the envelope is determined by the tooth contacts

The other borders are primarily determined by the TMJ anatomy and the ligaments

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What is temporomandibular joint??

It is the area where the mandible articulates with the cranium.
It is described as a complex , multiaxial ,synovial , condylar and ginglimoarthroidal joint.
Tmj is also known as CRANIOMANDIBULAR JOINT.
Assis.Prof.Radhwan Himmadi Hasan
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Assis.Prof.Radhwan Himmadi Hasan

Assis.Prof.Radhwan Himmadi Hasan

Cranial component

It is also known as mandibular/glenoid fossa.

• Mandibular component

The articular part of the mandible is an Ovoid condylar process.

• Tmj capsule

It is a thin sleeve fibrous tissue investing
joint completely.

Inside fibrous tissue capsule, a synovial

membrane is present.

Assis.Prof.Radhwan Himmadi Hasan

Ligaments:

Following are the ligaments associated with TEMPOROMANDIBULAR JOINT

• The lateral or temporomandibular ligament

• Sphenomandibular ligament
• Stylomandibular ligament

Assis.Prof.Radhwan Himmadi Hasan

Assis.Prof.Radhwan Himmadi Hasan

Assis.Prof.Radhwan Himmadi Hasan

Reference Positions

Centric Relation

Maximum Intercuspal Position

Postural Position – resting position

Assis.Prof.Radhwan Himmadi Hasan

Centric Relation
The position of the mandible in which the condyles are in the most superior and anterior position in the articular fossae, resting against the posterior slopes of the articular eminences with the articular discs interposed.

Condyle determined position

Repeatable, Reproducible,

Recordable

Assis.Prof.Radhwan Himmadi Hasan

Maximal Intercuspal Positionor Maximum Intercuspation

This is a position in which the maxillary and mandibular teeth make maximum surface contact with each other. The mandible is elevated as superiorly as possible in the sagittal plane.

Tooth determined position

Does not provide any information about the TMJ

In most people, MIP does not

coincide with CR

Assis.Prof.Radhwan Himmadi Hasan

Postural Position (PP)
Is the habitual position of the mandible when the patient is resting comfortably in the upright position and the condyles are in a neutral unstrained position in the glenoid fossae.
In this position there is an equilibrium between the forces acting on the mandible.
This position is determined by the muscles and the forces of gravity.

Assis.Prof.Radhwan Himmadi Hasan

Postural Position

In this position, the teeth are apart and there is a wedge space between the teeth.

The wedge shaped space is called the INTEROCCLUSAL SPACE and is usually 2-3mm between the incisors, 2mm between the premolars, and 0.75-1mm between the molars.

Assis.Prof.Radhwan Himmadi Hasan

three Basic Types of Movement

1-Hinge movement
• When the mandible is in centric relation the condyles can rotate around a horizontal axis up to an opening of 20-25 mm measured at the central incisors.
Assis.Prof.Radhwan Himmadi Hasan
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Assis.Prof.Radhwan Himmadi Hasan

2-Translatory movement

• If opening of the mandible continues beyond 20-25 mm then translation of the mandible occurs.

Assis.Prof.Radhwan Himmadi Hasan

Assis.Prof.Radhwan Himmadi Hasan

3-Lateral movements(right and left direction)

• The side to which the mandible is moving is called the WORKING SIDE
• The side that is opposite to the working side is called BALANCING OR NON WORKING SIDE

3) The condyle on the working side is called the WORKING OR ROTATING CONDYLE

4) The non-working condyle is called THE BALANCING OR THE ORBITING CONDYLE
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Border Movements

The mandibular movements are limited by ligaments, the articular surfaces of the TMJ, and the morphology of the teeth. The outer range of movement is reproducible and called border movements.
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Three-dimensional description of the Mandibular & Maxillary positioning

Also known as Axes of Rotation

Reference Planes
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Reference Planes

Sagittal Plane
Also known as a side view.

Assis.Prof.Radhwan Himmadi Hasan

Reference Planes

Sagittal Axis

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Border Movements in Sagittal Plane

Items of interest:

>Centric Relation
>Hinge axis movement
>Maximum Intercuspation
>Edge-to-edge incisal
>Maximum Protrusion
>Maximum Opening
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Border Movements in Sagittal Plane

CRC (Centric Relation Contact) will see the condyles in the glenoid fossa and closure of the mandible along the hinge axis, until first tooth contact is made (many times this is in the molar region).
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Border Movements in Sagittal Plane

CO (Centric Occlusion), or Maximum Intercuspation (MI), is achieved when the patient is told to get their maxillary and mandibular teeth together in a comfortable, contacting position.
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Border Movements in Sagittal Plane

The mandible will open along the hinge axis, with the condyles rotating within the glenoid fossa. The rotational movement will terminate at the Terminal Hinge Axis Position.
The Terminal Hinge Axis is the rotational movement that occurs from CR to the Terminal Hinge Axis position. The condyles are rotating completely within the glenoid fossa. It is a reproducible and consistent movement.

Assis.Prof.Radhwan Himmadi Hasan
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Border Movements in Sagittal Plane

Maximum Opening displays the most inferior position of the mandible, after the patient is instructed to open their mouth as wide as they can.
Assis.Prof.Radhwan Himmadi Hasan
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Border Movements in Sagittal Plane

Edge-to-Edge contact of Maxillary and Mandibular Incisors.

Mandible is protruded forward from MI, maintaining some type of tooth contact throughout.
Assis.Prof.Radhwan Himmadi Hasan
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Border Movements in Sagittal Plane

Maximum Protrusion position.

The teeth are in some degree of contact (usually in Premolar-Canine area) and mandible is pushed forward as far as possible.
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Border Movements in Sagittal Plane

CR
MI
E-T-E
MP
MOA
MO
HA
HAT
HA-MO

Legend:
CR = Centric Relation
MI = Maximum Intercuspation
E-T-E = Edge to Edge Incisal
MP = Maximum Protrusion Point
MOA = Maximum Opening Arc
MO = Maximum Opening Point
HA-MO = Hinge Axis to Maximum
Opening
HAT = Hinge Axis Terminating
Point
HA = Hinge Axis Arc
• CL
RP
RP = Rest Position or Postural
Position of the Mandible
CL = Chewing Loop
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Reference Planes

Horizontal Plane
Parallel to the Occlusal Plane or the floor

Assis.Prof.Radhwan Himmadi Hasan

Horizontal Axis

Imaginary line through both condyles
Reference Planes

Assis.Prof.Radhwan Himmadi Hasan

Border Movements in Horizontal Plane

Characteristically described as a “diamond” shape.

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Functional Range in Horizontal Border

As the mandible opens, the size of the horizontal plane border decreases until it reaches a “point” at the maximum opening position.
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