prostho vi- slides 5 - occlusal_considerations

8/14/2019 Prostho Vi- slides 5 - occlusal_considerations

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cc usa ons era ons

Art icu lato r Select ion fo r

Complete Dentu res

Part I & II

Khaled Q Al Hamad BDS Msc MRD RCSEd

Associate Professor

Department of Prosthodontics

Dent 445- Lecture 4 & 5


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Introduction to Occlusion

Centric Relation ( RCP) & Centric Occlusion ( ICP)

Mandibular MovementAnterior Guidance

Occlusal registrations for CD- clinical steps

Occlusal Schemes for CDArticulators


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Occlusion

Relation of the of the maxillary and mandibular teeth when in

functional contact during activity of the mandible.

An integral part within the stemato-gnathic system (SGS) that relatesteeth, not only to other teeth, but the other components of the SGSduring normal function, Para function and Dysfunction.

SGS: Teeth, TMJ, muscles, Periodontium.

Terminal Hinge Axis: horizontal axis between the condyles duringrotation with a terminal arc of closure at the mandibular incisor ofup to 25mm.


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RCP & ICP


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Centr ic Relation:The Maxillomandibular relationship in whichthe condyles articulate with thinnest avascular portion of theirrespective disks with the complex in the anterior-superiorposition against the shapes of the articular eminence

Retruded Contact Position(RCP):

the initial tooth contact upon closure when the condyles have

purely rotated whilst in their most superior unrestrained positionin the glenoid fossae.

I nter-cuspal Position(ICP): the complete intercuspation of teethregardless of the condylar position (Centric Occlusion)


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ICP is affected by:

mesial drift, tooth

wear, tilt and drifting,restoration in

supra/infra occlusion,

ICP is a habitual

position that can

change throughout life

while RCP is

anatomicallydetermined position

and thus constant and

more reproducible.

In 90% of the


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Significance Of ICP

Its the position in which vertical occlusal forces are

most effectively borne by the periodontium with teethlikely to be loaded axially.

Its the end point of the chewing cycle.

In every day practice, this is the position in whichrestorations are made.


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Significance of RCP

Most crowns are made usually to conform to ICP and

a slide from ICP to RCP is of no importance.Adjusting the contact in RCP is likely important:

When RCP involve a tooth you are about to prepare.

When reorganizing at increased VDO.

When you need space ( mandibular repositioning


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Mandibular Movement

When the mandible moves, teeth slide over each other.

This partly determined by: Shapes of the teeth( anterior guidance)

Anatomical constraints of the TMJ (Posterior guidance).

Both should be in harmony.


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Lateral movements is guidedby condyle- fossa relationship

and teeth relation ships. Working side:

Canine guidance

Group function.

Combination: initialgroup function thencanine rise towards theend.

Non-working side. ( not thebalancing side)

The side away fromwhich the mandible hasmoved.


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Occlusal Schemes for CD

Articulators


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Protrusive Movement

Anterior Guidance (AG): its the effect of the contact

between the incisal edges of the lower teeth and thatof palatal surfaces of the upper teeth on mandibularmovement.

Incisal guidance.

Steep incisal guidance: increased posterior separation (e.g. class II divII)

Possible increase in load on the anterior teeth.

Condylar guidance.(30-60/average:45)


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Requirements for AG

Patient comfort

Smooth guidance, that is , there are no mandibular

deflection.

Acceptable aesthetics & phonetics.

Minimal movement of guidance teeth

Posterior disocclusion.

No cementation failure of fracture of the interim

restorations.


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Significance

Guidance teeth are repeatedly loaded non axially.

Manifestations of problems with guidance:

Fracture

Wear

Tooth migration/mobility

TMJ Dysfunction


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Articulators


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Video 1

Mandibular rest position


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Video 2

Adjusting vertical dimension to obtain the required

free way space


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Video 3

Registering the maxilo- mandibular relation


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Articulators

Poster ior teeth-cuspal incl ination


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Poster ior teeth-cuspal incl ination.

Anatomic teeth: 30. 33 & 45

Semi-anatomic: 20

Flat or monoplane teeth: 0

Ideally, teeth should be anatomic

ff i i h i f d


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effective in chewing food.

aesthetically pleasing.

designed to be set in balanced articulation.

Potential problems denture instability when the articulation is not balanced leading to

trauma to the denture bearing area.

Non-anatomic teeth

designed to be flat and

allow even occlusal contact without deflection during excursivemovement.

can be used with monoplane occlusal schemes

set in a simple hinge articulator.

useful when the alveolar ridge is markedly resorbed and is difficult toprovide a stable mandibular denture.

Potential problems

chewing efficiency is relatively in effective

aesthetic requirements might be jeopardized.


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advantages to anatomic teeth: -1. Can establish mechanical and physiologic occlusion.


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C p y g -2. Penetrates food more easily. -3. Articulate in harmony with TMJ and masticatory muscles. -4. Resists rotation of denture base through interdigitation with

cusps. -5. Better esthetics. -6. Less trauma to underlying tissues.

disadvantages to anatomic teeth: -1. Requires and exacting technique.

-2. Lateral torque. -3. Relining and rebasing is difficult.

advantages to non-anatomic teeth: -1. They dont lock the mandible into one position. -2. They minimize horizontal pressure due to no inclined planes. -3. Closure can occur in more than one position---centric relation

can be an area rather than a point. -4. They can easily adapt to Class II & III jaw relationships. -5. They accommodate to changes in vertical and horizontal

relations of ridges. -6. Relining and rebasing is easier.

-7. They improve denture stability.

Teeth-Materials


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The materials from which posterior teeth are constructed are:

Acrylic resin.

Porcelain. Composite resin.

Metal onlays.

The acrylic teeth are the most widely used. They are easy to bond to acrylic(chemically)and easy to adjust. Their major disadvantages are their poor

resistance to wear. Porcelain has much better resistance to wear but it is difficultto be adjusted and does not bond to the denture base (Mechanical). Patient may

complain that the teeth make noise when eating. Composite teeth are increasinglybeing used for denture opposing natural teeth. Finally, in cases in which the rate ofwear of the acrylic teeth has been extremely rapid, metal onlay restorations can be

incorporated onto the acrylic teeth.


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Arranging Anatomic Teeth to a Balanced Articulation.


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The anterior teeth are set to a low incisal guidance of 0.5

mm vertical and 1-2 mm horizontal overlaps.

Number of Posterior Teeth. The decision on this will

depend on the available space. Placing teeth on the

residual ridge incline as it ascends to the pad should

be avoided. If only three teeth are to be set, the firstpremolar is dropped.


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Balanced occlusion (anatomic teeth)

advantages: -1. Esthetics

-2. Better food penetration

-3. Anatomic occlusion is arranged in harmony with the

muscles of masticationdisadvantages:

-1. Precise technique required for set-up

-2. Cuspal inclines tend to create greater lateral forces that

can harm ridges -3. More time is required to establish a balanced occlusion

Balanced occlusion with non-anatomic teeth


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-although non-anatomic teeth are usedhere, it should not be considered amonoplane occlusion.

-2 advantages to this scheme: -1. Can be used for patients with poor

neuromuscular coordination

-2. Less time involved with the set-up

-2 disadvantages of this scheme:

-1. Compensating curve may cause

same damaging effects as cuspalinclines

-2. Occlusal adjustments are moredifficult

Arranging Non-Anatomic Teeth to Monoplane Articulation.


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can have balanced andnon-balanced occlusion

with non-anatomic teeth.

the principles:

0 condylar guidance 0 incisal guidance

0 cusp height

flat occlusal plane

no vertical overlap

A simple hinge articulator. The maxillary posterior teeth are set one at atime with Mandibular wax rim and its references and guides for tooth

l Th ill h i i d l d i h h fl


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placement. The maxillary teeth are positioned to occlude with the flatsurface of the Mandibular wax rim. There should be 1-2mm ofhorizontal overlap of the maxillary facial cusps in relation to the

Mandibular wax rim. When completed, the occlusal surfaces of themaxillary teeth should be flat against the Mandibular wax rim.

The Mandibular teeth are arranged so they will maximally contact theupper teeth. Each tooth is arranged in maximum contact of the flatlingual cusp of the opposing upper tooth contacting the central groovearea of the Mandibular tooth. The antero-posterior relation is not critical.

Any combination of the premolars and molars can be used to fill theavailable space. The posterior limit of the extent of these teeth is thepoint at which the Mandibular ridge begins to curve upward toward theretromolar pad.

There is no attempt to eliminate deflective contacts in lateral orprotrusive

Basically, the patient can clench and grind in and around maximumintercuspation during functional and non functional activities. Howeversome deflective contacts of the posterior will be experienced.


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advantages of monoplane occlusion:

-1. More adaptable to unusual jaw relations

-2. Can be used in cross-bite cases

-3. The mand does not get locked into one position -4. Greater comfort and efficiency

-5. Improved denture stability

-6. Accommodates to changes in horizontal and vertical relations

-7. Relining and rebasing are easier

disadvantages to monoplane occlusion:

-1. Less efficient mastication -2. Esthetically inferior

-3. Clogging of occlusal surfaces

-4. Poor food penetration

-5. Difficult to establish balanced occlusion

indication for monoplane occlusion:

-1. Class II or III malocclusion

-2. Severe residual ridge resorption -3. Excessive interarch distance

-4. Poor neuromuscular skills

-5. Poor patient adaptability

Lingualized Occlusion


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Utilizes anatomic teeth for themaxillary denture and modified nonanatomic or semi anatomic teeth for themandibular denture.

An attempt to maintain the esthetic &food penetration advantages of theanatomic form while maintaining themechanical freedom of the nonanatomic form.

Lingualized occlusion should not beconfused with placement of themandibular teeth lingual to the ridgecrest.

Indications for Lingualized Occlusion.


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Can be used in most denture combinations.

particularly helpful when the patient places a high priority on

aesthetics but a non anatomic occlusal scheme is indicated by theoral conditions such as: Severe resorption. Class II jaw relationship. Displaceable supporting tissue.

can be also used effectively when a complete denture opposes aremovable partial denture.

The goal for bilateral balanced occlusion with lingualizedocclusion Usually the desired range of balanced occlusion can be

achieved before the anterior teeth make contact. In situationswhere the anterior teeth would contact before achieving thedesired range of bilateral balanced occlusion, the verticaloverlap of the anterior teeth can be reduced to approach anincisal guidance of zero.

A slight compensating curve will be necessary to achievecontinuous osterior contacts anterior to the centric relation.

Principles of Lingualized Occlusion.

Anatomic posterior teeth (33 or 30 degree) are used for the maxillary denture.

T th f ith i t li l f l


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Tooth forms with prominent lingual cusps are useful.

Non-anatomic or semi-anatomic teeth are used for the mandibular denture.

A narrow occlusal table is preferred when severe resorption of the residual ridge hasoccurred.

selective grinding is always necessary regardless of specific tooth material.

Selective grinding smoothes the fossae of the mandibular teeth, lowers marginalridges,

forms slight buccal and lingual inclines. This create a slight concavity in the occlusalsurface.

Maxillary lingual cusps should contact mandibular teeth in centric relation.

Balancing and working contacts should occur only on the maxillary lingual cusps. This helps to reduce lateral movement of the lower denture placing occlusal forces more

lingual to and toward the centre of the mandibular teeth. On the balancing side, themaxillary lingual cusps contact the mandibular buccal cusps as is customary with anatomictooth arrangement.

Protrusive balancing contacts should occur only between the maxillary lingual cusps andthe lower teeth.

Selective grinding for the protrusive movements should be done on the mandibular teeth

only so that the lateral balancing contacts and the vertical dimension of occlusion are notchanged.

The desired range of balanced occlusion can be achieved before the anterior teeth makecontact.

In situations where the anterior teeth would contact before achieving the desired rangeof bilateral balanced occlusion, the vertical overlap of the anterior teeth can be reducedto approach an incisal guidance of zero.

A slight compensating curve will be necessary to achieve continuous posterior contacts


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Advantages of Lingualized occlusion.


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Cusp form is more natural in appearance compared to

non-anatomic tooth form.Good penetration of food bolus is possible.

Bilateral balanced occlusion is readily achieved for a

region around centric relation.

Vertical forces are centralized on the mandibular

teeth.


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Articulators

Articulators


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An articulator may be defined as "a mechanicaldevice that represents the TMJ & Jaw members towhich maxillary and mandibular casts may beattached to simulate jaw movement".

Function: to act as the patient in his absence. It can

simulate but not duplicate all manidibular movement.However, it can be programmed with certain records toallow fabrication of the restorations.

Advantages of Articulator over the patient

B i li i f h i l i i ll li ll


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Better visualization of the patient occlusion, especially lingually.

Patient cooperation is not a factor.

The refinement of complete denture occlusion is extremelydifficult in the mouth because of shifting denture bases andresiliency of the supporting tissues.

Considerable more chair side time when utilizing the patient

mouth as the articulator. More procedures can be assigned to auxiliary personnel when not

using the patient mouth.

There is no Tongue, saliva, cheeks with the mechanical articulator

Classifications

Class I Simple holding instruments capable of accepting a single static


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Class I.Simple holding instruments capable of accepting a single staticregistration. Vertical motion only.

Class II.

permit horizontal as well as vertical movements but no face bow transfer. can be further subdivided according to mechanism of programming the

eccentric motion:

average or arbitrary values,

based on theories of occlusion.

Class III. simulate condylar pathways by using averages or mechanical equivalents

for all or part of the motion.

allow for a face bow transfer.

further subdivided according to the mechanism of programming theeccentric motion :static protrusive or static lateral check records.

Class IV. accept three-dimensional dynamic registrations.

further subdivided according to the method of programming the articulator:

Stereographic recordings,

Pantographic recordings,

Electronic recordings.

Classifications


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According to TMJ Resemblance

ARCON. The element representing the condyle is attachedto the lower member of the articulator while the condylar

fossae is on the upper member).

NON-ARCON. The opposite of the above.

According to adjustability Non-adjustable (Class I).

Semi-adjustable (Class II & III).

Fully-adjustable (Class IV).


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B l l f d b h i l l d


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-Bennett angle: angle formed by the sagittal plane and

the path of the advancing condyle during lateralmandibular movements as viewed in the horizontal

plane.

-Fisher angle: angle formed by the inclinations of the

protrusive and non-working side condylar paths asviewed in the sagittal plane.


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Simple hinge A

l


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llo

wsrotat

ionalmo

vemento

n


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Functionally generated path


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Average Value

Allow limited range of protrusive


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g pand lateral movements based onaverage values through a fixedcondylar guidance.

Usually set:

30 for condylar guidance.

15 for incisal guidance.

110 for intercondylar distance.

Indication: couple of posteriorcrowns and short span bridge.

Semi adjustable/ARCON

These are the workhorses for


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These are the workhorses forrestorative treatment.

Require a facebow. Interocclusal record in

protrusive, lateralexcursions to programcondylar guidance andBennet angle and shift.

Hanaus formula:L=(H/8)+ 12

H:Horizontalcondylar inclination

L: Lateral condylarinclination

Maxillary cast is related to an arbitrary axis of


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Maxillary cast is related to an arbitrary axis of

rotation.Condylar guidance is variable but in a straight line.

Some adjustment of the incisal table is possible

Semi adjustable/NON-ARCON


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Fully adjustable

Maxillary is mounted using Kinematic facebow.


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y g

Mandibular movement is recorded by pantographs, electronic jaw

tracking devices (Cardiax), or Sterographic or fossa-moulded Using intra-oral clutches with studs which mould soft acrylic during border

movement. These dynamically carved intra oral 3D records are thentransferred to the articultor. Self cure acrylic is then added to fossa insertand the and the articulator excursions are guided by the intra-oralengravings.

pantographs


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Sterographic or fossa-moulded


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Denar Cadiax Compact System with Gamma Dental Software


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DENAR D5A

Fully adjustable.

Arcon construction simulates


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Arcon construction simulatestrue anatomical structure.

Adjustments: protrusive angle0-60 degrees; immediate sideshift 0-4mm; progressive sideshift 0-30 degrees rear wall30 degrees backward; topwall 30 degrees up, 30

degrees down; intercondylardistance 90-150mm.

Medial and Superior wallinserts: removable for customgrinding; choice of

curvatures. Adjustable incisal table (T3),

custom step incisal table (T2)and long centric incisal pin(P2) are standard.

Lingual visibility allows for

eas viewin and access to

prostho vi- slides 5 - occlusal_considerations

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