Occlusion presentation

 Alignment and Occlusion of Permanent
teeth
 Anatomical alignment of teeth
 Anatomical occlusion of teeth
 Mandibular posture
 Radiographic appearance of jaws and
teeth
 Clinical considerations

Occlusion: contacts between teeth.
Masticatory
System
Teeth
Periodontal
Tissues
Articulatory
System
TMJ Muscles Occlusion

 Tooth alignment: the arrangement
of teeth within the dental arches
 Occlusion :relationship of dental
arched when tooth contact is made.
 Neutral zone: the space in which there
is equilibrium of forces so the teeth attain
a position of relative stability (ex: tongue thrust,
abnormal lip posture change the zone)

 Static occlusion
 Centric Occlusion: maximum intercuspation
(Syn. for this are Intercuspation Position, Bite of
Convenience, Habitual Bite.)

 Centric Relation: jaw relationship
 Anatomical
 Conceptual
 Geometrical

 Anatomical: head of condyle in
the most superior part of distal
facing incline in glenoid fossa,
uppermost and foremost.
(controversy: uppermost and midmost.)
 Conceptual: muscles that support
mandible in the most relaxed and least
strained position.
 Geometrical: head of condyle in terminal hinge axis.

 Ideal Occlusion
 Normal Occlusion
 Malocclusion

 What’s an ideal occlusion?
 CO=CR
 Features:
› Multiple simultaneous contacts
› No cuspal incline contacts
› Occlusal contacts in line with LA of teeth
› Smooth guidance contacts

 What’s an ideal occlusion?
 Teeth are aligned such that masticatory
loads are within physiological range.
 Mastication involves alternating bilateral
jaw movement (not habitual or unilateral
biting)
 In the rest position the FWS is correct for the
individual concerned
 The tooth alignment is aesthetically
pleasing to its possessor

 Normal Occlusion
 Angle the mesiobuccal cusp of the upper
molar occluded in the buccal grove of the
lower molar and the teeth were arranged in
a smoothly curving line of occlusion
Normal occlusion and Class I malocclusion
differed in the arrangement of the teeth
relative to the line of occlusion.
Aesthetically pleasing , functionally stable

 Malocclusion
 defined as an anomaly impedes
function, and requiring treatment
 Proffit: Malalignment of individual teeth
in each arch deviating from the smooth
curve of line by being; tipped,
displaced, rotated, in infra-occlusion, in
supraocclusion.
 anteroposterior, vertical or transverse.

 Anatomical Alignment
 Upper &lower form a catenary curve
 No spaces or rotations of teeth within
the arch.
 Angle’s line of occlusion
Line of occlusion for max. arch pass
through the cingula of ant. Teeth ,and
central fossa of post.
 Line of occlusion for the mand. Arch
runs along the incisal edges of ant. teeth and along the buccal
cusps pf pos. teeth

 Pic of ant. Middle and pos segments in
coronal and sagital planes

 Table of average width of dental arches
(males)
 Females less by 1mm

 Angulations and Axial positioning of
individual teeth

 Mandibular premolars and molars

 Curvatures of the teeth and arches
 Occlusal planes and teeth axes are
curved not straight.
 The curved axes of the teeth have a
tendency to parallelism and inclined
mesially
 Forces of mastication strike the teeth that
there is a mesial component of force
plus the vertical force.

What if the arches were not curved?
The arches might not be stable and the
mastication loads might be at an
unfavorable
Angle to the teeth .

 Curvatures of the teeth and arches
 The occlusal plane has three curvatures:

 1. Curve of spee: it refers to the
anterioposterior curvature of the occlusal
surface, beginning at the tip of the lower
cuspid and following cusp tip of bicuspids
and molars continuing as an arc through
the condyle .
 The mand. Curve of spee is concave , max
convex
 They are opposite but complementary ,
help to achieve occlusal balance during
mastication by encouraging contact in
more than one area of the arch.

 2. Curve of Wilson:
aligned in the transverse plane ,
in a medio-lateral curve of the posterior teeth.
 purpose of this arc is to complement
paths of condyles during movements
of man.
 Max and mand. Wilson curves are opposite
and complementary

 3. Curve of Monson :
• It is a combination of Spee
and Wilson curves.
• This curve is within sagittal
and coronal planes.
• This curve is convex for the
occlusal surfaces of the upper
dental arch and concave for
the lower dental arch

 When the upper & lower dental arches are
occluded in centric occlusion the curves of the
upper & lower arches become
identical and form a segment
of a sphere of four inches
radius with center of sphere
is at the glabella

With age - attrition planes become flat

 Anatomical Occlusion Of Teeth:
 Symetrical occlusal positions:
 Centric occlusion, bilateral protrusive
position
 Asymetrical occlusal position :
 Lateral movement (side to side)

 Centric Occlusal position according to
the orthodontist Angle:
 Each arch is bilaterally symmetrical
Relies on the first molars to the intercuspal position btw the
teeth in CO
 Each max. tooth will contact
its corresponding man.
Antagonist and its distal
neighbour ,(the only exception
is the man first incisor and third
molars)

 Max arch is larger than the mand arch
there is slight overlap of the mand. arch
by the max. arch, the max teeth extend
a few mm beyond the mand. buccal
cusps OVERJET (2-3mm)horizontal
overlap
 OVERBITE:vertical overlap (2-3 mm),
where the palatal surfaces of max
incisors overlap the incisal third of the
labial surface of man incisors

 Centric stops: (holding contacts)
 When the 32 teeth are in contact in anatomic
centric occlusion there are 138 centric stops
 The slops of the max palatal cusps make stops
coincident with the stops within the central
fossae of the mandibular posterior teeth
 Central fossa of max. teeth coincide with the
stops on slopes of buccal cusps of man. Pos
teeth
 Cusps seated in the central fossae ->supporting
cusps

 The tips of max buccal cusps
and mad. Lingual cusps
remain unmarked
Mand. Incisors have the
stops on the insical edges,
max incisors stops are on the
palatal surfaces .
 Clinically :using the articulating paper
 With age ->flat cusps->centric stops altered

 Angle’s Classification
 Gives the relation of the arches in an A-P
direction using the max and man first
permanent molars

 Angle’s Class 1 malocclusion:
the MB cusp of the max first molar
occludes with the mid-buccal groove of
the man. first molar tooth .

 Andrew added:
 1. The distal surface of the distal
marginal ridge of the max molar
contacts and occludes with the mesial
surface of the mesial marginal ridge of
the man second molar
 2. The MP cusp of max molar sits in the
central fossa of man molar

Angle’s class 2 malocclusion
Max first molars
occluding at least half
a cusp more mesial to
the mand first permanent
molars than the standard
anatomical position.
Class 2 div 1: max incisors are proclined
Class 2 div 2:max incisors are retroclined
(centrals,retro where as the laterals proclined)

 Angle’s class 3 malocclusion
The max first molar occludes at least half a
cusp more distal to the man first molar , MB
cusp of max upper first molar occlude distal to
the mid buccal groove of the man first molar

 Classification based on canine
relationships:
 Class 1:the cusp of max canine occludes in
the embrasure between the mand canine
and first premolar
 Class 2: the max canine occludes mesial to
that in class 1
 Class 3: the max canine occludes distal to
that in class 1


 Classification based in incisor relationships:
 Classification based on incisors relation is a
more informative method of describing
malocclusion
 Class 1 incisor relation:
 The incisal margin of the mand. Incisors
occlude with or lie directely below the
middle third of the palatal surfaces of max
incisors (below the cingulum plateau)

 Class 2 incisor relationship:
 The incisal margins of the mand incisors
are related to the gingival third of the
palatal surfaces of the max incisors.
 Div 1:max incisors are proclined with
increased overjet
 Div 2: max central incisors are retroclined
***check laura

 Class 3 incisor relationship:
 The incisal margins of the man incisors lie
infront of the cingulum plateau of the
palatal surfaces of max incisors. (related
o the incisal third of palatal surfaces of
max incisors
 Reversed or reduced OJ

 Forms of malocclusion:
1. Crowding :the condition
where the teeth are out of
the line of the dental arch
(teeth- arch size discrepancy).
 The last tooth to erupt usually
manifest the crowding (max canine, man 2nd
premolar)

2. Anterior open bite: occurs where there is
no incisors overlap or contact.
*Causes: Skeletal anomalies,
Dental abnormalities,
Habits (thumb sucking ,abnormal
swallowing patterns)
Physiological related to the
stage of eruption

3. Crossbite: a transverse abnormality of
dental arches where the mand teeth are in
a buccal version to the max teeth
Unilateral or bilateral
Discrepancy in the width of dental bases
and may involve the displacement of the
mand to one side to obtain maximal
intercuspation

 Free way space: (FWS)
 the separation between the occlusal surfaces
of the maxillary and mandibular teeth when
the mandible is in its rest position (2-3mm).
 Physiological state ,body posture and fatigue
are short term influences that can change the
FWS
 Ageing and the removal of occlusal contacts
affect the resting position.
 Physical properties of the soft tissues are
responsible for the rest position and not the
tonic avtivity of the elevator muscles of the
jaw.

 Assessing FWS
 Facial measurements FWS = RVD - OVD
 Speech (look for closest speaking
distance, listen)
 Appearance
 Two Dots technique (nose/chin)

 Cephalometric analysis of lateral skull
radiographs
 Access:
 General skeletal morphology (relation
btw jaws and cranial base )
 Evaluate the direction and amount of
growth
 Soft tissue analysis
 Determine dento skeletal relationship

 Cephalometric analysis of jaw
relationships and facial forms

 Cephalometric growth studies
 A frequently employed
strategy to assess growth
relies upon superimposition
of successive cephalometric
tracings of the same individual
at different ages.

 Soft tissue analysis :
 Soft tissue should be clear,
lips in their habitual posture.
 To undertake such analysis
reference is often made to
3 planes:
 The H line
 The upper lip tangent(ULT)
 The aesthetic line(AL)

 Mandible fracture:
 Mand fractures most common in order:
neck of the condyle, angle and ramus, body.
 Fracture in the neck caused by blow to the
chin or the body of mand on the contralateral
side->displaced anteriomedially.
 Fracture line at the angle extends downward
backward ,the masseter,temporalis,medial
pterygoid pull the displaced fragment upwards
inward forward .
 Fractures of the body occur canine and first
molar region as a result of direct blow .

 Variation in tooth morphology :
1. Number of teeth
Hypodontia (partial
anodontia)
Hyperdontia
3rd molars 25% >sec
premolar>max lat incisor
2.5%
Supplemental
,supernumerary
(mesiodens)
Syndromes:ectodermal
dysplasia (anodontia)
Midline btw the centrals

2. Size of teeth
Microdontia Macrodontia
(megadontia)
Usually max sec incisor, 3rd
molars
Geminated tooth
(enamel organ partially
divide ->large ,double
tooth

3. Fusion and transposition of teeth
Fusion Transposition
Two adjacent teeth fuse
together
The positional
interchange of two
adjacent teeth
Total number of teeth is
less than normal
Most common: max
canine transposed with
max first premolar
Distinguishing it from
geminated tooth
Mand canine with mand
lateral
High incidence of
congenitally absent teeth
,peg shped lat and/or
suppernumerary

4. Root and Pulp morphology :
Depending on x-ray to obtain information
about root morphology, but its 2D
Variation in root morphology will have
clinical implications:
 Curved
 Dilacerated
 Hypercementosis
 Concrescence

 Care must be taken :
 Extraction of upper molars and maxillary
sinus
 Roots of third molars and ID nerve
 Roots of mand premolars if long with
mental nerve

Occlusion presentation

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