Occlusion that results when the mandible is protruded

forward from centric position.When the mandible is

moved into protrusion, the mandibular incisors, or front

teeth of the mandible, are moved 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 movementCondyles 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

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):

The temporomandibular joint is the joint of the jaw and is

frequently referred to as TMJ. The TMJ is a bilateral synovial

articulation between the mandible and temporal bone. The

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

the joint: the uppertemporal bone which is part of the

cranium (skull), and the lower jawbone or mandible

Functions of articular dischelping 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