Protrusive movements

1. Protrusive occlusion
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.

2. 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

3. 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
.

4. 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.
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

5. 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

6. 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.
..
.