dr laila amin (occlusion2)
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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
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