Occlusion It is the act or process of closure or of

being closed or shut off.

.

Angle’s classification of

occlusion

It is base on the interdigitation of

first molar teeth major groups

depending on the anteroposterior

jaw relationship.

It is base on interdigitation

of first molar teeth

person’s profile

Classifications

Class I: normal occlusion or

neutr-occlussion.

Class II: disto-occlusion or

retrognathic.

Class III: mesio-occlusion or

prognathic

Classifications (natural teeth)

The classes are based on:

A) person’s profile

B) Position of mesio buccal cusp

of the upper first molar relative

to the buccal facial developmental

groove of the lower first molar.

C) Upper anterior and lower anterior

tooth relations in terms of vertical and

horizontal overlap.

The classes are based on: A-Profile B- Upper 1st molar C-vertical

and horizontal overlap.

Class I

A) Normal profile.

B) The mesio buccal cusp of the upper

first molar falls in the buccal groove

of the lower molar when the teeth are

in centric occlusion.

C) In the anterior area, there is a

normal range of horizontal overlap(0-2)

There is a normal range of vertical

overlap (1 to 5 mm).

Class I

Class II

A) Retruded (retrognathic)profile

B) The mesio buccal cusp of the

upper first molar falls anterior to

the buccal groove of the lower

first molar in centric occlusion.

C) In anterior area , horizontal

overlaps in excess of 10 mm are

not common

Class II

Class III

A) Protruded (prognathic profile).

B) Mesio buccal cusp or upper

first molar falls posterior to the

buccal groove of the lower first

molar in centric occlusion.

C) In the anterior area the upper

and lower anterior are usuallay

edge to edge.

Class III

For edentulous person

In addition to person’s profile

Mentolabial sulcus curvature

indicates to maxillo-mandibular

relationship.

In Angle’s class I the mentolabial

sulcus show gentle curvature which

represent an obtuse angle

For edentulous person

In Angle’s class II:retrusion, the

mento-labial sulcus presents

an acute angle in which the lower lip

is folded towards the chin

For edentulous person

In Angle’s class III: In protruded

maxillo-mandibular relation ship ,the

mento-labial sulcus may form an angle

of almost 180. maxillo-mandibular

relationship can detected even before

study casts are made.

Classifications (edentulous person)

class I Class II Class III

Natural and artificial teeth

Differences between natural and

artificial occlusion

Points of comparison 1-Angle’classification

2-Neuromuscular system

3-surrounding tissues

4- Mandibular movement

5- Stability and retention

6-Tissues stimulation

7- Pressure of occlusion

8-Vertical off forces

9- Incising

10- Mastication

11- Bilateral balance

5

1-Angle’s Classification

Natural

It is based on profile

and the

interdigitation first

molar teeth

Artificial

It is based on profile

and mentolabial

sulcus curvature

2-Neuro-muscular system

Natural

Posses adaptive

mechanism as wear,

extrusion and drifting of

teeth (protective reflexes)

Highly innervations

through proprioceptive

gives control during

function.

Artificial

Prosthesis rests on

tissues that change progressively and

irreversibly.

If cusp interfere or

prematurities exist as

mandible returns to this

position, the bases will

shift on supporting tissue.

Neuro-muscular system

Neuro-muscular system natural teeth artificial teeth

3-Surrounding tissues

Natural

Teeth surrounded by bone and considered as fixed except some

movement within the limits of periodontal attachment.

Teeth are retained by periodontal tissues that are uniquely innervated and structure.

Artificial

Teeth are attached to movable base resting on the soft tissue that can displaced .The displacement of tissues varies between individual

Poor nerve ending and

the teeth on the bases are seated on slippery tissue.

4- Mandibular movement

Natural

Permits both

functional and para-

fuctional movement.

Artificial

Permits both

functional with

increase in para-

functional movement.

5-Stability and retention

Natural

Not depend upon

contact of teeth in one

part of the arch to

balance tooth contact

in another part.

Artificial

Partially depending

upon the contact of

tooth in one part of

the arch to balance

tooth contact in

another part of arch.

6- Tissues stimulation

Natural

Bone receives stimulation, tensile in

nature, through the pull of the periodontal

attachment. Tensile stimulation contributes to normal bone physiology.

Artificial

Denture does not posses this stimulation. When teeth

attached to the denture base resting on tissues covered the bone exhibit to force ,this exerting force is compressive in nature which causes

bone resorption

7- Pressure of occlusion

Natural

The teeth receive individual pressure of occlusion and can move

independently, the teeth

can migrate to adjust occlusal pressure.

Mal occlusion of natural teeth may be

uneventful for years.

Artificial

The teeth move as a unite on their base.

Mal occlusion on artificial teeth evokes an immediate response and involves all the teeth and the base.

8- Vertical off forces

Natural

Non vertical forces on

natural teeth during

function affect only

the teeth involved and

are usually well

tolerated .

Artificial

The effect involves all

of the teeth on the

base it is usually

traumatic to the

supporting structures.

9- Incising

Natural

Incising with the

natural teeth does not

affect the posterior

teeth.

Artificial

Incising with artificial

teeth affects all teeth

on the base.

10- Mastication

Natural

The second molar is

favored area for

masticating hard food

owing to more

favorable leverage

and power.

Artificial

Heavy pressures of

mastication in the

second molar region

with artificial teeth

will tilt the base and

shift it , if it is on an

inclined foundation.

11-Bilateral balance

Natural

Bilateral balance is

rarely found. If

present it is

considered balancing

side interference

Artificial

Is generally

considered for base

stability.

Meet Again

Smile muscles

Anatomy of a smile: the pull

of a variety of small, but very

responsive facial muscles.

Concepts of Occlusion

Occlusion must satisfy physiologic

requirements and be acceptable to the

patients

Factors of occlusion (Laws of

articulation)

Articulation is a change from occlusal position to

another while the occlusal surfaces or cusps are

in contact. The harmonious occlusal position of

teeth have three positions of three position of

articulation are recognized;

1-Working position (side)

2-Balancing position (side)

3- Protrusive position

1- in working position (side)

The side on which the patient is masticating

called working side , opposite side is

Balancing side.

Contacts of teeth made on the side of the

articulation toward which mandible is

moved during working.

Centric relation working and balancing

Centric relation working and balancing

In working side

The buccal cusps of the upper teeth are in

the embrasure and between the cusps of the

lower posterior teeth .The upper anterior

teeth just contact the lower anterior teeth.

2-In balancing position (non working side)

That side of the mandible moves toward

the median line in a lateral excursion. The

palatal cusps of the upper posterior teeth

contact the incline of the buccal cusps of

lower posterior.

3- In protrusive position

A minimum three point contact must be

established between the upper and lower

centrals and between posterior on each side

It is desirable to balance the teeth so that

all cusps will touch in this position.

Balanced Occlusion

If the balanced occlusion and articulation is not established the stability of the denture will be affected seriously.

The reasons for obtaining balanced occlusion are:

1- to produce efficient mastication

2- to help in stabilizing the denture

3- to prevent the denture movement during chewing movement

The reasons for obtaining balanced occlusion

1- to produce efficient

mastication

2- to help in stabilizing

the denture

3- to prevent the denture

movement during

chewing movement

Laws of Articulation

1-Curve of Spee

2- Curve of Monson

3-The compensating curve

4- Occlusal plane

1-Curve of Spee

1-Curve of Spee

2- Curve of Monson

3-The compensating curve

4- Occlusal plane

Factors that affect occlusal

Balance

There are five factors involved in eccentric occlusal balance in complete denture to achieve simultaneous gliding occlusal contacts from centric occlusion to eccentric occlusal position.

1-Condylar guidance

2- Incisal guidance

3-Plane of occlusion

4-Compensating curve

5- Cusp height

1-Condylar guidance

Due to the path the condyle follows in the

temporomandibular joint has been assessed

at different levels of importance.

2-Incisal guidance

It is usually expressed in degrees of

angulations from the horizontal by a line

drawn in the sagittal plane between the

incisal edges of the upper and lower incisor

teeth when closed in centric occlusion.

Correlation between condylar and incisal

guidance

3- Plane of occlusion

Is established in the anterior by the height

of the lower cuspid , which is nearly

coincident with the commissural of the

mouth, and in the posterior by the height of

the retromolar pad. It is also related to the

ala tragus line or Camper’s line.

4-Compensating curve

One of the more important factors in establishing a balanced occlusion.

It is determined by the inclination of the posterior teeth and their vertical relationship to the occlusal plane so that the occlusal surface results in a curve that is in harmony with movement of the mandible as guided posteriorly by the condylar path.

5- Cusp height

Cusps on teeth or inclination of cuspless

teeth are also important determinants as

they modify the effect of the plane of

occlusion and the compensating curve.

Balanced Articulation

(Static and Dynamic)

When the mandible moved with the teeth in

contact from one position of occlusion to

another without any interference.

E.g. from lateral to tooth position that the

teeth should glide across each other.

Take care

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