lecture 3- occlusion

8/13/2019 Lecture 3- Occlusion

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FUNDAMENTALS OF

OCCLUSION

Fundamentals of Fixed

Prosthodontics-Shillingburgh

(Pp 11-23)

DR. MOHAMMAD AL AMRIDR. MOHAMMAD AL AMRI


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IMPORTANCE OF OCCLUSION

The long-term success of a restoration isdependent upon maintenance of occlusal

harmony.

Fabricate a restoration that will not create

iatrogenic occlusal disease.


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GOALS OF RESTORATIVE

TREATMENT

To create occlusal contacts in posterior teeththat stabilize instead of creating deflective

contacts that may destablize the mandibular

position.

The occlusion of a restoration should bemade in harmony with the optimum condylar

position CENTRIC RELATION.


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CENTRIC RELATION

An anteriorly, superiorlybraced position along the

articular eminence of the

glenoid fossa, with thearticular disc interposed

between the condyle and

eminence.


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CENTRIC RELATION

This position of the condyles in theglenoid fossae has been discussed and

debated for many years.

It is used in dentistry as a repeatablereference position for mounting casts.


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CENTRIC RELATION

Many methods used to guide the mandibleinto an ideal position.position.

Earlier concepts of centric relation involvedEarlier concepts of centric relation involvedthe most posterior condylar position in thethe most posterior condylar position in thefossa.fossa.

The condyle was forcefully manipulated intoThe condyle was forcefully manipulated intothe rearmost, uppermost and midmostthe rearmost, uppermost and midmostposition called theposition called the RUMRUM position using theposition using the

chin guidance technique.chin guidance technique.


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PHYSIOLOGICAL POSITION

The more recent concept describes aphysiological position regarding themusculoskeletal relationship of thestructures.

It is not a forced position, but is gentlyguided by the operator using the bilateralmethod or by allowing the natural muscleaction to place the condyle in aphysiologically unstrained position.


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MANDIBULAR MOVEMENT

Mandibular movementcan be broken down

into a series of motionthat occur around three

different axes


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MANDIBULAR MOVEMENT

Various mandibularmovements are composed

of motion occurring

concurrently about oneaxis or more.


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MANDIBULAR MOVEMENT

The up and down motion of the

mandible is a combination oftwo movements.

A pure hinge movement occursas a result of the condyles

rotating in the lower

compartment of the TMJ withina 10-13 degree arc which

creates a 20-25 mm separation

of the anterior teeth.


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MANDIBULAR MOVEMENT

There is also somegliding (translation)

movement in theupper compartment

during maximum

mouth opening


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MANDIBULAR MOVEMENT

(Protrusive)

When the mandibleslides forward so that

the maxillary and

mandibular anteriorteeth are in end-to-end

relationship, it is in a

protrusive position. Ideally the anterior segment of the mandible

travel a path guided by the contacts between the

anterior teeth, with complete disocclusion of theposterior teeth.


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MANDIBULAR MOVEMENT

(Lateral excursion)

Mandibular movement to one

side will place it in working

side and the other side will

be the nonworking side.

In this type of movement, the

condyle on the NW side will

arc forward and medially.

The condyle on the workingside will shift laterally and

slightly posteriorly.


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BENNETT MOVEMENT

During lateral excursion, the

bodily shift of the mandiblein the direction of theworking side was firstdescribed by BENNETT.

The angle formed in thehorizontal plane between

the pathway of the NWcondyle (the mandibulartranslation) and the sagittalplane is called the

BENNETT ANGLE.


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OBJECTIVES OF RESTORATIVE

DENTISTRY

One of the objectives of restorativedentistry is to place teeth in harmony

with the TMJ.

When teeth are not in harmony with thejoints and with mandibular movement,

an INTERFERENCE is said to exist.


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OPTIMUM OCCLUSION

1. In closure, the condyle is in the mostsuperoanterior position in the glenoidfossa. The posterior teeth are in solid

and even contacts, and the anteriorteeth are in slightly lighter contact.

2. Occlusal forces are in long axes ofteeth

3. In lateral excursion, working-sidecontacts (preferably on the canines)disocclude or separate the NW teethinstantly

4. In protrusive excursion, the anteriorteeth contacts will disocclude theposterior teeth.

5. In an upright position, the posteriorteeth contact more heavily thananterior teeth.


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ORGANIZATION OF OCCLUSION

There are three recognized concepts

that describe the manner in whichteeth should and should not contact in

the various functional and excursive

positions of the mandible:

1. Bilateral balanced occlusion.

2. Unilateral balanced occlusion(group function).

3. Mutually protected occlusion

(canine protected occlusion).


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BILATERAL BALANCED

OCCLUSION

It is a prosthodontic concept whichdictates that a maximum number of teethshould contact in all excursive positions ofthe mandible.

Particularly useful in complete dentureconstruction.

Difficult type of arrangement to achieve.

Excessive frictional wear of teeth due tomultiple contacts during excursivemovements.


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UNILATERAL BALANCED

OCCLUSION

Commonly known as group function.

All teeth on the working side to be in contactduring lateral excursion.

Teeth on the nonworking side are contouredto be free of contact.

Teeth on the working side distributes theocclusal load favorably.

Absence of contact on the nonworking sideprevents teeth from being subjected todestructive, obliquely directed forces.


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MUTUALLY PROTECTED OCCLUSION

Also known as canine

protected occlusion. The anterior teeth bear all

the load and the posterior

teeth are disoccluded inany excursive position of

the mandible.

In the intercuspal position,

the posterior teeth contact

and relieve the anteriorteeth.


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ARTICULATORS

Pp-25-32


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ARTICULATOR

An articulator is a

mechanical devicethat simulates the

movements of the

mandible.


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ARTICULATOR

Principle employed inthe use of articulator isthe mechanicalreplication of the pathof movement of theposterior determinants-the TMJ.

The instrument is thenused in the fabricationof dental restorationsthat are in harmony

with those movements.


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BORDER MOVEMENT

The outer limit of allexcursive movements

made by the mandible

BORDER MOVEMENT.

All functional movements

are confined to the three

dimensional envelope of

movement.


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BORDER MOVEMENT

Limited by the

ligaments

Highly repeatable

Useful in setting the

various adjustmentson the mechanicalfossae of an

articulator


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ARTICULATOR

Articulators vary widely

in the accuracy withwhich they reproduce

the movements of the

mandible

Classification:

1 . Non-adjustable

2 . Semi-adjustable

3 . Fully-adjustable


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NON-ADJUSTABLE ARTICULATOR

Usually a small instrument.

Capable of only a hinge

movement.

Distance between the teeth

and the axis of rotation on

the small instrument is

shorter than it is in the

skull with the resultant

loss of accuracy.


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SEMI-ADJUSTABLE ARTICULTOR

Large size allows close

approximation of the

anatomic distance between

the axis of rotation and the

teeth

The radius of movement

produced on the articulatorwill reproduce the tooth

closure arc with relative

accuracy.


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SEMI-ADJUSTABLE ARTICULATOR

Semi-adjustable

articulator reproducesthe direction and endpoint but not theimmediate track ofsome condylarmovements.

Intercondylar distanceare not totally

adjustable.


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FULLY-ADJUSTABLE ARTICULATOR

Most accurate instrument.

Designed to reproduce the

entire character of bordermovement.

Intercondylar distance iscompletely adjustable.


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FULLY-ADJUSTABLE ARTICULATOR

It is expensive and

time-consuming.

Demands high degree

of skill.

Primarily used forextensive treatment,

requiring the

reconstruction of the

entire occlusion


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USES OF ARTICULATORS

Diagnosis : accurate

relation of diagnosticcasts allow visualexamination of the

opposing jaw andtooth relation.

Fabrication ofrestoration such ascrowns, FPD, RPD

and complete denture.


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ARCON AND NON-ARCON

ARTICULATORS

There are two basic designs used in thefabrication of articulators:

ARCON

NON-ARCON


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ARCON ARTICULATOR

Condylar elements are

placed in the lower member

and the mechanical fossae

in the upper member of the

articulator simulating the

human TMJ; e.g. :

WHIP-MIX ARTICULATOR


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Semi-adjustable arcon articulator


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There are twoversions:

1. Old version- straight

condylar housing with

adjustable intercondylarwidth and bennett angle


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2. New version- curvedcondylar housing with

intercondylar width fixed

at medium..Adjustable immediate

side shift


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THE TOOTH-TRANSVERSE

HORIZONTAL AXIS RELATIONSHIP

To achieve the highestdegree of accuracy from

an articulator, the casts

mounted on it should beclosing around an axis of

rotation that is as close as

possible to the transversehorizontal (hinge) axis of

the patients mandible.


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FACEBOW

Transfers the

relationship of the

maxillary teeth,the

transversehorizontal axis and

a third reference

point from thepatients skull to the

articulating device.


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FACEBOW

There are two types:

1 .Arbitrary

2 . Kinematic


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ARBITRARY FACEBOW

A facebow that employs

an approximate locationof the hinge axis basedon anatomic average.

There are numeroustechniques used for

arbitrarily locating thehinge axis to serve as aset of posterior reference

points for the facebow.


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QUICK MOUNT FACEBOW

Used with Whip Mix

Articulator.

Caliper-style facebow.

Designed to be self-

centering so little time

is wasted in centering

the bite fork and

adjusting individual

side arms.


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QUICK MOUNT FACEBOW

Posterior referencepoints - ExternalAuditory Meatus.

Anterior reference

point - Nasion


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QUICK MOUNT FACEBOW

Mounting maxillarycast- HorizontalCondylar Guidanceset at FB positionor 30 degrees

Upper member of

the articulatorshould rest on thetransverse bar ofthe facebow.


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KINEMATIC FACEBOW

Utilizes the true

hinge axis


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PANTOGRAHIC RECORDING

It captures all the

characteristics of the

mandibular border

movements from itsretruded position to

its most forward and

most lateral position


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PANTOGRAPHIC RECORDING

The tracing can be

utilized to its fullest

advantage when usingthe fully adjustable

articulator


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MAXILLARY CUSTOM TRAY


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MAXILLARY CUSTOM TRAY

OCCLUSAL STOPS ONNON FUNCTIONAL CUSPS

MINIMUM OF THREE

STOPPERS


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MANDIBULAR CUSTOM TRAY


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CUSTOM TRAYS


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ANTERIOR DETERMINANT OFOCCLUSION

Fundamentals of Fixed Prosthodontics

Shillingburg, et al 1997, 3rd edition,pages 22,23 & 54, 55.

DR. MOHAMMAD AL AMRI


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Hanaus Quint

By modifying the following five factors, a scheme ofocclusion can be developed that will suit a particular

patient best.

1. Condylar guidance

2. Incisal guidance

3. Occlusal plane orientation

4. Compensating curves

5. Height of the Cusp

Except for the condylar guidance, all other factorscan be modified during the fabrication of a prosthesis

and the anterior guidance plays a predominant role.


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Condylar Guidance Vs Incisal / Anterior Guidance


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Anterior Guidance

The influence of contacting surfaces of anterior

teeth on mandibular movements.

The influence of contacting surfaces of the guidepin and anterior guide table on articulatormovements.

The fabrication of a relationship of the anteriorteeth preventing the posterior tooth contact in all

eccentric mandibular movements.


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Protrusive Incisal Path

The track of the incisal edgesof the mandibular teeth frommaximum intercuspation toedge-to-edge occlusion.


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Protrusive Incisal Path Angle

The angle formed by the protrusive incisal path and the horizontal

reference plane is the protrusive incisal path inclination. It rangesfrom 50 70 degrees and is often 5-10 steeper than the sagittal

condylar guidance.


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Incisal Guide Angle

The angle formed by thehorizontal plane of occlusionand a line in the sagittal planebetween the incisal edges ofmaxillary & mandibular central

incisors when the teeth are inmaximum intercuspation.

The angle formed in the sagittalplane between the horizontalplane and the slope of the

incisal guide table.


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Importance of Anterior Guidance

Opening and closing of the mandible is simply a

rotation of the condyles in the articular fossae.


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As anterior guidance is normally steeper than the

condylar guidance, the anterior teeth guide themandible downwards during protrusive or lateral

movement

and ..


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(during protrusive movement)

.. produces dis-occlusion or separation of the

posterior teeth.

I t f A t i G id


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(during lateral movement)


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Anterior guidance is linked to the combination of

horizontal & vertical overlap of the anterior teeth

and

can affect the occlusal surface morphology of

the posterior teeth.

Inter relationship between Vertical &


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Inter-relationship between Vertical &

Horizontal Overlap of the Anterior teeth

Anterior guidance can be made steeper by eitherincreasing the vertical overlap (overbite) A-B, or by

reducing the horizontal overlap (over jet) C-A of theanterior teeth.

Anterior guidance can be made shallow by either

decreasing the overbite B-A or increasing the overjet A-C of the anterior teeth.

Condylar Guidance & Posterior tooth Morphology


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Condylar Guidance & Posterior tooth Morphology

(without considering the role of A.G.)

Shallow condylar guidance normally requiresshallow cusp angle or short cusp height and

steeper condylar guidance requires steep cusp

angle or longer cusp height.

Condylar side shift & Posterior tooth Morphology


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Condylar side-shift & Posterior tooth Morphology

(without considering the role of A.G.)

side shift + No side shiftSimilarly, in the presence of an immediate lateral side

shift during lateral movement (Bennetts movement)

the cusp height and cusp angle should be shallow.


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Influence of Anterior Guidance on

Posterior tooth Morphology

Influence of A G on Posterior tooth


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Influence of A.G. on Posterior tooth

Morphology(Effect of Overbite)

Greater overbite produces Less overbite - less

more disocclusion hence disocclusion - shorterpermits longer cusp height Cusp height



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Morphology

(Effect of Over jet)

Greater over jet necessitates Less over jet needs

short cusp height long cusp height

I fl f A G P t i t th


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Morphology

Summarizing,

greater anterior guidance allows posterior

teeth to have longer cusp height

&

smaller anterior guidance allows posteriorteeth to have shorter cusp height.


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Fabrication of Custom IncisalGuide Table

Preservation of the Anterior Guidance

of the Natural Teeth for itsReproduction in the

Fixed Prosthesis

To preserve and then to reproduce the anterior


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p p

guidance provided by the natural teeth in the waxed

up crowns, custom incisal guide table should befabricated.

St i th F b i ti f C t


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Steps in the Fabrication of Custom

Anterior Guide Table

1. The mounted studycasts should beexamined on thearticulator to assessthe anterior guidanceand to remove anynonworking sideinterference so thatthe articulator movesfreely.


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2. If the anterior guidance provided by theremaining teeth is inadequate, restore

it to an optimal form with inlay wax, or

denture tooth on the cast.



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3. Raise the incisal pin (round end down) so that itwill miss the plastic incisal table by at least 1mm

during all movements.



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4. Place one or two drops of auto-polymerizingacrylic resin monomer on the plastic incisal

table.



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5. Mix one half scoop of self curing acrylic resin

polymer with monomer and place a smallamount on the plastic table.

As the resin develops more body, additional

material is added until there is 6mm or inch ofresin on the plastic table.



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p


6. Lubricate the round end of the incisal pin and

the functioning surfaces of the anterior teethwith petrolatum jelly.

Close the articulator in centric occlusion so that

the incisal guide pin penetrates into the softresin.



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p


7. Move the articulator repeatedly through allmandibular movements (protrusive and both

laterals)



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p


The tip of the incisal pin molds the resin to conform toall the movements of the articulator. These

movements should be repeated until the resin haspolymerized.



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8. Trim off the excess acrylic resin with a

bur after it has polymerized completely.



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p


The tip of the incisal pin has acted as a stylus in

forming the registration of the anterior guidance.It will now be possible to duplicate the influence of

the anterior teeth on the movement of the casts,

even though the anterior teeth are now preparedand the incisal edges shortened.


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SILICONE PUTTY


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SILICONE PUTTY


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lecture 3- occlusion

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