Occlusion

Dr \ Laila Amin

Dr\Laila Amin

Objectives:

Define centric occlusion\function

Illustrate supporting/guiding cusps

Enumerate key of occlusion

Dr\Laila Amin

Objectives :

Enumerate angles classification

Relate importance of proper

occlusion with the clinical practice

Classify mandibular movement

Dr\Laila Amin

Centric Occlusion

maximum inter-

cuspation

most retrusive unstrained positionof condyles in glenoid fossa

GLENOID FOSSA

TOOTH –TO- TOOTH RELATIONSHIP

1

Dr\Laila Amin

7-Occlusal contact and intercusp Relations of all Teeth in One Arch with those in the Opposing Arch in Centric Occlusion.

a

b

c

a) Supporting cusps. b) guiding cusps

c) centric stop

Dr\Laila Amin

Supporting cusps: the cusp that makes contact with a centric stop in the opposing tooth

Centric stops: areas of contact that a supporting cusp makes with opposing teeth

Dr\Laila Amin

Supporting cusps:1)Maintain the distance

between max, man2)Support the vertical

dimension3)Play the major role in

masticationDr\Laila Amin

Dr\Laila Amin

Dr\Laila Amin

Guiding Cusps: the cusps that are free of contact during centric occlusion

1)Minimize tissue impingement2)Maintain the food bolus on

occlusal table3)Guide the mandible during

movement Dr\Laila Amin

key of occlusion

Dr\Laila Amin

1.First permanent teeth to erupt in the oral cavity.

2.Occupy a central position in the jaw (antro-posteriorly).

Key of Occlusion:Maxillary & mandibular 1st permanent molars

serve as “Key of occlusion”:

Why?

Dr\Laila Amin

3- Their positions in the jaws are guided by the presence of the deciduous molars preceding them.

4- Their eruption is not disturbed as they have no predecessors.

5- 6 is considered more accurate than 6 as it is attached to a bone fixed to the base of the skull.

Dr\Laila Amin

Key of occlusion : 6 6

Key of occlusion means:• in normal jaw relation, • normal sized teeth ,

•teeth in correct position,

MB cusp of upper 6 occlude in the MBG of lower 6, this normal relation of these two teeth is called

key of occlusionDr\Laila Amin

Angle’s Classification:Class I:• Normal

Class II: Retrognathic• Retruded profile• Deficient in chin length

Class III: Prognathic• Protruded profile• Excessive in chin length

Dr\Laila Amin

MB cusp 6

MB groove 6

Classification of Occlusion

Class I :

Centric occlusion:

Angle’s Classification:

MB

MB groove

Dr\Laila Amin

Class II malocclusion

Retrognathic profile

Classification of Occlusion

Dr\Laila Amin

Dr\Laila Amin

Class III malocclusion

Anterior cross bite

Dr\Laila Amin

Dr\Laila Amin

Class I

Class II

Class III

Angle’s Classification:

Dr\Laila Amin

The centric relation of the teeth in centric occlusion

Dr\Laila Amin

Centric Occlusion of Permanent Teeth

Each tooth in a dental

arch occludes with two

teeth in

the opposing arch ,

except:

the mandibular central

incisor

the maxillary third molar.

1

1 2

5

5

4

Dr\Laila Amin

The centric relation of the teeth

in centric occlusion

The median plane is coincident in two jaws

Upper tooth has labial relation to lower incisor in

centric relationDr\Laila Amin

Incisal ridges is free of contact , labial relation to

labioincisal portion of lower central & lateral incisor

Cingulum above the lingual embrasure of 1&2 lower

incisor

Mesial outline is in line with the mesial outline of lower 1

incisor

distal outline is centered above labial surface of lower 2

incisor

Upper central incisors:

Dr\Laila Amin

Upper lateral incisors

MOL: above the labial surface of lower 2

DOL: above the labial surface of lower 3

Dr\Laila Amin

Lower 1, 2

Lower 1

LI R: contact 1 at junction

incisal and middle third

MOL: with midline

DOL: below mesial 2\3 1

Lower 2

LIR: contact 1,2 at junction of

incisal , middle third

MOL: below distal 1\3 of 1

DOL: below 2

Dr\Laila Amin

Lower 3Upper 3Below lingnal embrasure 2,3above labial embrasure lower

3,4

Cusp

Free, below ling embrasure 2,3Free, above ling embrasure 3,4Cingulum

Below lingual surface 2Above the cusp tip lower 3MOL

Below ling surface 3Above lower 4 (BC)DOL

Dr\Laila Amin

Facial relation premolars\molars in centric

occlusion

Dr\Laila Amin

lingual relation of premolars\molars in

centric occlusion

Dr\Laila Amin

Dr\Laila Amin

Dr\Laila Amin

SUMMARY STATEMENTS:

1. ML cusp of each maxillary

molar occludes in the central

fossa of the opposing

mandibular molar.

2. MB cusp of each mandibular

molar occludes on the MMR of

the opposing maxillary molar.

Dr\Laila Amin

3- Functional cusps:

B cusps of mandibular posterior teeth.

L cusps of maxillary posterior teeth.

Dr\Laila Amin

Centric occlusion relation of the deciduous teeth:

At age 3 years the child has centric occlusion similar to permanent teeth

Dr\Laila Amin

Dr\Laila Amin

8-The Occlusal Contact and IntercuspRelations of all the Teeth During the Various

Functional mandibular movements.

Mandibular movements are: (rotating movement )

A.Symmetrical bilateral movements:• Depression.• Elevation.• Protrusion.• Retrusion.

B.Asymmetrical bilateral movements:• Right lateral movements.• Left lateral movements.

Dr\Laila Amin

Rest position of the mandible :

•When the mandible is at rest lower teeth are not in contactwith the upper teeth as there is a space of 2 mm in-between

the two arches freeway space .

Dr\Laila Amin

functional relations of mandibular

movements:

Protrusive occlusal relation.

Retrusive occlusal relation.

Right occlusal relation.

Left occlusal relation

Dr\Laila Amin

•The mandibular archbears a forward,anterior relation to itscentric relation with themaxillary arch.

•Biting or shearing foodmaterial

1) Protrusive occlusal relation:

Dr\Laila Amin

•Retrusion of the mandible,•the mandibular teeth will have posterior relation to centric occlusion with the maxillary arch.

•Very limited and non functional movement.

2)Retrusive occlusal relation:

Dr\Laila Amin

•The mandibular dental arch is placed in a right or left lateral relation to centric occlusion with the maxillary arch.

3) Right and left lateral occlusal relation:

Dr\Laila Amin

The masticatory cycle of posterior teeth:

•The working side shows the buccal cusps of maxillary and mandibular teeth to be in contact.

•The balancing side shows contact of lingual cusps of the maxillary teeth with the buccal cusps of mandibular teeth.

•Then both sides move to centric occlusion.

Dr\Laila Amin

Working side Balancing side

Dr\Laila Amin

Dr\Laila Amin

The masticatory cycle of anterior teeth:

• In bitting

• the functioning side is located at the anterior teeth

• the balancing side at the posterior teeth.

Dr\Laila Amin

Dr\Laila Amin

Dr\Laila Amin

The term key of occlusion refers to the

relationship of the 1.Buccal cusps of the mandibular molars to the

central fossae of the maxillary molars

2.Maxillary and mandibular canines

3.Mesiobuccal cusp of the maxillary first molar

to the mesiobuccal groove of the mandibular

first molar

4.Mandible and maxilla

Dr\Laila Amin

When the mandible is in its physiologic rest

position, there is

1.Premature contact of teeth

2.No contact of teeth

3.Maximum contact of teeth

4.Slight contact of teeth

Dr\Laila Amin

When a permanent mandibular canine is

located distal to the maxillary canine during

full closure of the mandible, this is regarded

as a1.Class I occlusion

2.Class II occlusion

3.Class II occlusion

Dr\Laila Amin

Class III malocclusion is very often when 1.The maxillary arch is larger than the mandibular

arch

2.Maxillary and mandibular arches are proportion to

each other

3.The maxillary arch is smaller than the mandibular

arch

Dr\Laila Amin

Dr\Laila Amin