5 Jaw Relation, Artificial Teeth,Articulators

8/13/2019 5 Jaw Relation, Artificial Teeth,Articulators

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JAW RELATION

MAXILLOMANDIBULAR

RELATIONSHIP


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Jaw Relation

refers to anyrelation or positionof the mandible to

the maxilla

According to the Glossary of Prosthodonticterms, the term JAW RELATIONis objectionable,MAXILLOMANDIBULAR RELATIONSHIPisrecommended


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Jaw Relation lassification

Vertical Horizontal Orientation

VDR VDO VD at otherposition

Centric Relation Eccentric Relations

Protrusion Lateral Excursion


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1. Orientation Relation

establish references in the cranium

relationship of the jaw to the TMJ oropening axis of the jaw

opening axis can be located by using aFACE BOW


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FACE BOW

a U-shape framecaliper-like device thatis used to

record the relationshipof the jaws to theopening axis of the TMJ

to orient the casts in

this same relationshipto the opening axis ofthe articulator


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Indications for Face Bow Use

When balanced occlusion is desired

When cusp form teeth are used

When interocclusal check records are used

When occlusal vertical dimension is to be changedduring teeth setting

For diagnostic mounting and treatment planning

For making occlusal corrections after dentureprocessing


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Classification OfFace Bow

Arbitrary

Gives approximate values

Condylar rods placedapprox over the condyle

Fork attached to maxillaryocclusal rim

Approx determines theterminal hinge axis

used for CD procedures

Kinematic

fixed values

Condylar rods placedaccurately over thecondyles

Fork attached to

mandibular rimAccurately determines the

terminal hinge axis

Used commonly for fixed

or RPD


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2. Vertical Relation / VerticalDimension

It is the verticalmeasurement of the facebetween any twoarbitrarily selected pointsconveniently located oneabove and one below themouth usually in themidline

Types of Vertical Relation / Dimension1. Vertical Dimension at Rest (VDR)2. Vertical Dimension at Occlusion (VDO)3. Vertical Dimension at other position


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A. Vertical Dimension at Rest (VDR)

vertical dimension when themandible is in the physiologicrest position

established by muscle andgravity

used as a guide to the lostvertical dimension at occlusion(VDO)

measured when the head isupright in position and not

supported by the headrest


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Physiologic rest position

position of the mandible when all musclesthat closes and opens the jaws are in astate of minimal tonic contraction sufficient

only to maintain posture


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Interocclusal Distance / FreewaySpace / FWS

space or gap between theupper and lower teeth when

the mandible is in physiologicrest position

usually 2-4mm when observedat the position of the first

premolars essential because it maintains

health of periodontal tissue

when teeth are present


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B. Vertical Dimension at Occlusion(VDO)

established by the naturalteeth when present and inocclusion

established by the verticalheight of 2 dentures/OCR incontact

computed by the formulaVDO = VDR - FWS


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C. Vertical Dimensionat Other Position

no significance in CD construction

vertical dimension when mouth is halfopen or wide open


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Consequences of Increase VerticalDimension

trauma on the tissuedue premature striking ofteeth

possibility of pain in the TMJ

more awkward to manipulatedue to longerleverage

clicking of dentures

more easily displaced

face appears long

patient could hardly closes his mouth

rapid destruction of residual ridges

facial muscles appears strained


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Consequences of Decrease VerticalDimension

reduces function of the muscles with resultant loss ofmuscle tone

cause creases at the corners of the mouth cause loss of space in the oral cavity with an adverse

effect on the eustachian tubemay affect hearing may produce trauma in the TMJ chin appears to far forward shrunk appearance of the face vermillion borders of the lips reduced approximately to a

line lips lose their fullness face is flabby instead of being firm corners of the mouth turn down or droop


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Methods of Determining

Vertical Dimension


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PHYSIOLOGIC

METHODS


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1. Physiologic Rest Position

Swallow and relax

presence of interocclusal distance of 2-4 mm at thepremolar area

Niswongers method Two marking are made, one on the upper lip below

the nasal septum, the other on the chin. Patient istold to swallow and relax.

The distance between the two marks are measured adifference of 2-4mm when VDO is subtracted fromVDR

if less than 2mm, VD is probably too great

if greater than 4mm, VD is considered too small


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2. Phonetics

consist of listening to speech sounds Using m sound, presence of 2-4mm space observing the relationships of teeth during the

production of ch, s, and j sounds ( bring anterior teethclose together but no contact)

presence of speaking space of not more than 1mm at theanteriors

Using thirty-three, enough space for tip of the tongue toprotrude between the anteriors

Using f or v sounds, maxillary incisal edge, lightly contact

the lower lip Silvermans closest speaking space (1mm), presence of

space during the function of speech if speaking space is too largeVD is considered too small if speaking space is too smallVD is probably too great


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3. Esthetics

Facial Esthetics

tone of skin throughout theface should be the same

Willis Method Distance between the outer

canthus of the eye and cornerof the mouth should be equal

to the distance between thelower border of the septum ofthe nose and lower border ofthe chin


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4. Swallowing

presence of a very light contact at thebeginning of the swallowing cycle

if denture occlusion is missingVD maybetoo small

if there is difficultyVD is probably toogreat


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5. Tactile Sense

Patient tactile sense Patient is asked if the rims appear to touch too soon,

or if the jaw closes too much or if it feels just right

Boos Bimeter

A device the measures the biting force Maximum biting force ocurs at VDO

Lytles method Using a central bearing plate and pin

Electromyography Rest position determined by recording minimal activity

of muscles of mastication


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6. Patient Perceived Comfort


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Mechanical Methods


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Mechanical Methods

Ridge relation Incisive papilla to mandibular incisors

- approximately 4mm in natural dentition

Parallelism of ridges

Measurement of former denture Preextraction records

Profile radiographs have been used but cannot be

considered adequate

Cast of teeth in occlusion give an indication of the amount of

space required between the ridges forthe teeth of this size

Facial measurement

use of Willis gauge


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HORIZONTAL JAW RELATION


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Horizontal Jaw Relation

refers to the front to back, sideto side relation of the mandibleto the maxilla

Classifications of Horizontal JawRelation

1.Centric relationthe basic horizontal jaw relation2. Eccentric relation

A. protrusionB. right and left lateral excursionC. all intermediate position


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Centric relation

A maxillo-mandibularrelationship in which thecondyles articulate with thethinnest avascular portion of

their respective disks withthe complex in the anterior-superior position against theslopes of the articulareminence

the most retruded positionof the mandible against themaxilla at the establishedvertical dimension


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Centric Relationvs

Centric Occlusion


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Centric Relation vs Centric Occlusion

Centric Relation This position is independent of tooth

contact and is repeatable position

Centric Occlusion

The occlusion of opposing teeth when themandible is in centric relation.

In natural dentition this may or may notcoincide with maximum inter-cuspal

position In complete denture CR=CO=MIP


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Significance of Centric relation

if centric relation andcentric occlusion donot coincide, it will

result to dentureinstability and pain ordiscomfort


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METHODS OF RETRUDING THEMANDIBLE

1. Passive Method

dentist guidemandible in terminal

hinge axismovement

2. Active Method

patient responds toinstruction byactively retrudingthe mandible


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Techniques to retrudethe mandible

finger guidance

central bearing point

stretch-relax exercisestongue curling backward

swallowing

reclining the patientpalpation of temporal

muscle


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METHODS OF RECORDING

CENTRIC RELATION


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1. Static Method

placing the mandible incentric relation, thenmaking a record of the

2 rims to each other. advantage

minimal displacement ofrecording bases in

relation to thesupporting bone


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2. Functional Method

involve functional activity or movement of themandible at the time the record is made

includes:

A. chew-in technique by Needles, House, Essig,Paterson

B. swallowing

disadvantagecauses lateral and anteroposterior displacementof the record base


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3. Graphic Method

involve the used ofintraoral or extraoraltracing devices, with a

central bearing pointsecured to the record base


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Gothic Arch Tracing

d d / l


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Recording Medium /MaterialsUsed in Recording CR

plaster

wax

ZOE paste

cold cure acrylic resin

warm staple wires

pins


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Biologic

- Realeff

- Neuromuscular problems

- TMJ abnormalities

Mechanical

- Ill fitting bases- Excessive pressure

Psychological- Patient factors

- Operators abilities

Complications in Recording CR


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Mandibular Movements


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Mandibular Movements occur during

- mastication

- speech

- swallowing

- respiration

- facial expression

- parafunctional habits like clenching and

bruxism


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TMJ a ginglymoarthrodial joint

(sliding, hinge joint)

Structures

1. Bony Structures

- condyle

- glenoid fossa

- articular tubercle

2. Articular disc

3. Articular capsule

4. LigamentsA. temporomandibularligaments

B. sphenomandibular ligaments

C. stylomandibular ligaments


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1.Hinge movement

2. Translatory movement

- forward or protrusive- direct lateral side shift

(Bennett movement)

- translatory movement thatoccurs when the mouth isopened wide


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Envelope of Motion

Border movements ofthe mandible

Types

1. Envelope of motionin sagittal plane

2. Envelope of motionin the frontal plane

3. Envelope of motionin the horizontal plane


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ARTICULATORS


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ARTICULATORS

a mechanical devicethat represents theTMJ and jaw

members to whichmaxillary andmandibular castscan be attached


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Parts of an Articulator Upper & lower arm/member

Represents the maxilla & mandiblewhere casts are atached

Mounting plates Connects the casts to the articular arm

Condylar analogues

Represents the condyle Condylar guidance

Represents the slope of the articulareminence which guides the movement ofthe condyle

Can be fixed or adjustable or customized

Incisal guide pin Represents the vertical dimension atocclusion

Incisal guide table Represents the lingual slopes of the

maxillary anterior teeth along which thelower incisor move

Can be fixed or adjustable or customized


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Classification of

Articulators


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1. Simple Hinge

accept only centricrelation record

can be opened andclosed only

also called one-dimensional instrumentbecause only oneinterocclusal record is

necessary for itsadjustment and use


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2. Mean value

allows lateral andprotrusivemovements based

on averagedeterminations

condylar guidanceangle and incisive

guidance are fixed,30 and 10 degreesrespectively


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3. Semi- adjustable

with individuallyadjustablecondylar guidancesin both the vertical

and horizontalplanes

accepts face-bowtransfer

interocclusalrecords can beused to record thecondylar guidance


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4. Fully Adjustable

a 3-dimensional articulatorthat requires a CR record,at least 2 lateral records,and some means for

controlling the height andinclination of the cusps

capable of reproducing jawmovements with great

accuracy Pantograph (consist of six

styli and tracing tables)use to produce tracings

called pantogram


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ARCON Articulator

a contraction of the wordsarticulator and condyle

means that the condylarguidance is located in the

upper member on thearticulator and the ball(condylar analogue) islocated in the lower

member

Better visualization andunderstanding of

mandibular movements

P og amming The


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Programming TheArticulator

Programming the condylarguidance

Horizontal condylar guidance

Use protrusive record (protrudemandible 6mm)

Lateral condylar guidance

Use lateral record or Hanaus Formula(H/8 +12)

Programing the incisal guidance

Horizontal guidance controls the anteroposterior

movement of the lower jaw

Lateral guidance

influence lateral movement of the

jaw (canine guidance)


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Occlusion

fi i i f


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Definition of Terms Occlusion

a static state used when opposing teeth are in contact without movement

Articulationis a dynamic state used when opposing teeth are in contact duringmovements of the mandible

Centric Occlusion Occlusion of opposing teeth when mandible is in centric relation

Eccentric Occlusion Occlusion other than centric occlusion that includes lateral and protrusive

occlusion

Balanced Occlusion(discussed later) Working Side

The side towards which the mandible moves in a lateral excursion

Balancing Side The side opposite the working side


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Natural Vs Artificial Occlusion

Natural Occlusion1. Supported by roots which are firmly

anchored to the bone2. Moves independently in their socket3. Malocclusion may remain uneventful

for years

4. Occlusal forces affect only theconcerned teeth

5. Nonvertical forces are tolerated muchbetter

6. Mastication is usually done in thesecond molar region

7. Bilateral bvalance is not naturallyfound and is considered detrimental8. The proprioceptive mechanism

enables the patient to avoidprematurities and gives him bettercontrol

Artificial Occlusion1. Supported by denture base placed on

slippery mucosa2. Move as uniton their base3. Malocclusionevokes immediate

instability and pain

4. Forces acting on a complete dentureaffect the whole base

5. Nonvertical forces are usually not welltolerated

6. The second premolar area is preferredfor mastication; mastication in the

second molar region can causeshifting of the base7. Bilateral balanceis usually considred

necessary for denture stability8. Poor feed back mechanism, so

neuromuscular control iscompromised

Functions of Complete Denture


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Functions of Complete DentureOcclusion

1. Improve masticatory function

2. Minimized harmful nonvertical or lateralforces

3. Contribute to the stability of the denturebases

4. Contribute to the health and preservation

of the alveolar bone and soft tissues5. Maintenance of the comfort and well-being

of the patient


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Complete Denture Occlusion

Balanced occlusion

Nonbalanced occlusion

Lingualized occlusion

Functionally generated occlusion


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BALANCED OCCLUSION

The bilateralsimultaneous, anterior& posterior occlusalcontact of teeth incentric & eccentric

Advantages Denture stability

Enhanced retention

Enhanced patient

comfort Maintenance of the

integrity of supportingtissue


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Occlusion

Factors Affecting Balanced Occlusion


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Factors Affecting Balanced Occlusion(Hanaus Quint)

1. Condylar Guidance- slope along which the

condyles travels when themandible protrudes

- Patient related factor

- Horizontal condylar guidance(protrusive record)

- Lateral condylar guidance

(L = H/8 + 12)

2. Incisal Guidance- the influence of the

contacting max & mandanteriors on the mandibularmovement


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3. Occlusal plane

established by thecuspids (commisures)

in the anterior and htof retromolar pad inthe posterior

4. Cuspal inclination

cuspal height


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5. Compensating curveartificial curves in CDto achieved a balanced

occlusionTypes

AnteroposteriorCompensating Curve

Lateral Curve (molarcurve, first premolarcurve)

Christensens


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Christensen sPhenomenon

is the development ofspaces between theupper and lower occlusalsurfaces at the distal of

the occlusal rims ordentures with thedownward and forwardmovement of the

mandible


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Bennett Movement

Mandibular lateral translation

Also known as Bennetts shift, direct lateral sideshift, side shift, laterotrusion

Cause separation during lateral movementDetermines cusp height and morphology

INTER RELATIONSHIP OF THE


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IncisalGuidance

CondylarGuidanceOcclusal

PlaneCompensating

Curve

Cusps

INTER-RELATIONSHIP OF THEFACTORS INFLUENCING

BALANCED OCCLUSION


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Nonbalanced occlusion

Nonanatomic teeth are used

Plane of occlusion parallel to residual ridge

No compensating curve

Lingualized occlusion

Upper lingual cusps are set into the lowercentral fossa; buccal cusps out of contact

Functionally generated occlusion

Maxillary teeth carve out a path in the waxplaced on the lower occlusal table, then waxis replaced with cast gold or metal alloys


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SELECTING

ARTIFICIAL TEETH


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Anterior Teeth Selection

color or shade

form or shape

size

material

*Pre-extraction Guides

- photograph

- diagnostic cast- radiograph

- teeth of close relative

- extracted teeth


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Sh d S l i


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Shade Selection

should be examined in 3 positions

outside of mouth, side of nose

gives hue, chroma, value

under the lip, incisal edge exposed

give effect of color when mouthis relaxed

under the lip, covers only thecervical

simulate smiling

do the squint test


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2. Form or Shape of Anterior Teeth

Outline of the face Square

Tapering

Ovoid Square tapering

Facial profile

- convex- straight

- concave

Sh f i h


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Form or Shape of Anterior Teeth

curvature of labial surface(incisal view)convexity or flatness of theface

Sex of the Patient Female

- More pronounced curvatures- rounded point angles

- more delicate appearance- Lateral incisors are smaller

Male- Squareness of teeth

3 Si f A t i T th


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3. Size of Anterior Teeth length of max central incisors

is 1/16 of the length of thefacefrom patients hairlineto the chin or is equal to thedistance from high lip line toincisal plane

width of max central incisorsis usually 1/16 of thebizygomatic distance

width of six anterior teeth isequal to the bizygomaticdistance divided by 3.3ordistance between the 2cuspid lines


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B P l i


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B. Porcelain Advantages:

- Hard and wear resistant

- mastication is more efficient

Disadvantages:

- mechanical bonding by holes orpins

- much lower thermal expansionthus can produce stress indenture base

- very hard to adjust, glaze lostwith grinding

- may cause clicking noise oneating or in patient with hearingaids

- teeth may chip in used


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C. Composite Resin

-harder than acrylic but tends tocollect stains

D. Hard Acrylic

- more wear resistant than acrylic butdont have staining problem ofcomposite

P t i T th S l ti


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Posterior Teeth Selection

tooth formbuccolingual width

mesiodistal width

lengthcuspal inclines

materials ( porcelain, resin, metal

insert, teeth with metal occlusals)shade

1. Tooth Form


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1. Tooth Form(Classification of Posterior Teeth)

AnatomicA. Provide a more natural look to the denturesB. more efficient in masticationC. definite cusp to fossa relation

D. cuspal inclination facilitate the development ofbilateral balance in eccentric occlusal position

Non-anatomic

A. use in Class II and Class III jaw relationshipB. closure of the jaws over a broad contact areaC. creation of minimal horizontal pressures

2. Buccolingual Width


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2. Buccolingual Widthof the Posterior Teeth

should be greatly reduced

- to enhance the development of thecorrect form of the polished surface

- to reduce the amount of stress to thesupporting tissues


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4. Length of the Buccal Surface


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e g o e ucca Su aceof the Posterior Teeth

length of max. firstpremolars should be

comparable to themax. canines


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Materials Used


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Materials UsedAcrylic or Plastic

Inexpensive, easily available, easy to grind, absorbsstresses, does not wear opposing natural teeth andgold crowns

Porcelain Use in sufficient interridge space, well formed ridges,

superior esthetics, can cause wear of natural teethand gold crowns and bridges

Acrylic or Plastic with amalgam inserts To reduce the wear of resin when oppose by porcelain

teeth

Acrylic or Plastic with gold occlusalsurfaces When oppose by natural teeth, gold occlusal surfaces

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5 Jaw Relation, Artificial Teeth,Articulators