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.

MasticatorySystem

TeethPeriodontal

Tissues

ArticulatorySystem

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

Max premolars and molars

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

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. Posteeth

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 malocclusionMax 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




Mandibular posture



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)




Mandibular posture



pic for thr views

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)




Mandibular posture



Facial fractures

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,medialpterygoid 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 teethFusion 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

Education

Occlusion presentation