occlusion Protrusive

occlusion that results when the mandible is protruded forward

from centric position.

When the mandible is moved into protrusion, the

, or front teeth of the mandible, are moved incisors mandibular

so that they first come edge to edge with the maxillary (upper)

incisors and then surpass them, producing a temporary

underbite. This is accomplished by translation of the condyle

down the articular eminence (in the upper portion of the TMJ)

without any more than the slightest amount of rotation taking

place (in the lower portion of the TMJ), other than that

necessary to allow the mandibular incisors to come in front of

the maxillary incisors without running into them.

Forward movement •Condyles with their articular discs move downward &

forward along glenoid fossa & articular eminence

(sagittal condylar path.)

•Contraction of ext. pterygiod muscles on each side>

Condylar path:

The path taken by the condyle on TMJ during various mandibular

movements.

- Protrusive condylar path: the path followed by the condyle when the

mandible moves forward from centric position.

- lateral condylar path: the path followed by the condyle in the glenoid

fossa

when lateral movement is made.

- Incisal path : is the path taken by the incisal edges

of the lower incisors on the palatal surfaces of the the upper incisors till

egde to edge position

Muscles of protrusion:

Lateral pterygoid assisted by medial pterygoid

Lateral pterygoid Muscle Origin:

superior head: Sphenoid bone

Inferior head : Lateral pterygoid

plate.

Insertion: Neck of the condyle.

Function: Contraction of the 2 muscles causing

protrusion

Contraction of one muscle moves the

mandible to the other side

palpated by placing the index finger on the lateral

side of the alveolar ridge above the maxillary

molars

.

The tempo mandibular joint (TMJ):

and is jaw is the joint of the temporomandibular joint The

. The TMJ is a bilateral synovialTMJ frequently referred to as

articulation between the mandible and temporal bone. The name

: the joint of the joint is derived from the two bones which form the

), and theskull( cranium which is part of the temporal boneupper

.mandible lower jawbone or

There are six main components of the TMJ.

Mandibular condyles

Articular surface of the temporal bone

Capsule

Articular disc

Ligaments

Lateral pterygoid

Functions of articular disc

helping in smooth motion during mandibular movement

absorbing shocks to the jaw joint from chewing and other movements

The disc divides the joint into two compartments, upper & lower

The possible movement of lower compartment is a simple hinge

movement

While that in the upper compartment is a sliding movement

The relative factors of protrusive balanced occlusion and the relationship among them

OBJECTIVE:

The experiment was designed to study the condition for achieving

protrusive balanced occlusion and the factors involved in occlusal

equilibration.

METHODS:

For achieving protrusive balanced occlusion, the posterior teeth of

mandible always contacted with the posterior teeth of maxilla in the

process of protrusive occlusive movement. The angle between the line

of movement track of mandible cusp in the process of protrusive

occlusive movement and occlusion plane is called cusp movement

inclination. A formula of calculation was obtained by using mathematics

track and the conversion of coordinate axis.

RESULTS:

The focus of protrusive balanced occlusion is relationship between the

track of mandibular cusp movement and working incline of maxillary

cusp. The first condition achieving protrusive balanced occlusion is that

cusp movement inclination is equal to cusp working inclination of

maxilla. The factors affecting cusp movement inclination are condyle

path inclination; incisal path inclination and teeth coordinate. The

factors affecting working inclination of cusp are cusp inclination and long

axis obliquity.

CONCLUSION:

Cusp movement inclination is the basic and the most important concept

in protrusive balanced occlusion.

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