posterior schemes

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Selection of Posterior ToothSchemes for Dentures

Robert D. Grady DDS, FACPAssociate Professor

Division of Restorative SciencesUniversity of Minnesota

School of Dentistry

Occlusal Scheme:

Systematic arrangement of artificialdenture teeth for function and comfort.

“The golden rule is that there are no golden rules.”George Bernard Shaw, 1903

Different schools of thought

+

Inconclusive research

=

Operator’s choice

Adaptability

“Patient adaptability, physically andpsychologically, trumps all other factors.”

Bob Grady, 2007

Denture Success

! Adaptability

! Operator Skill (verbal and technical)

! Vertical Dimension of Occlusion

! Centric Relation

! Esthetics

! Accurate impressions

! Occlusal Scheme

Occlusal Scheme Selection

! Investigators have not shown one type of dentureocclusion to be :

– superior in function

– safer to oral structures

– more acceptable to patients

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Goals of Complete Denture Occlusion

! Minimize trauma to thesupporting structures

! Preserve remaining structures

! Enhance stability

! Enhance mastication

! Esthetics

In addition we would like to decrease lateralforces to the residual ridges.

General Concepts of Denture Occlusion

! Common Features– Simultaneous, bilateral posterior contact in centric

relation (centric occlusion)

– Centralization of centric occlusal forces over themandibular residual ridges

" Buccal-Lingually

" Anterior-Posteriorly

– Functional anatomy is the main determinant of denturetooth position

Types of Patients

! Age

! Physical ability and anatomy

! Coordination/adaptability

! Jaw relationship

! House classification

! Previous denture experience

! Parafunctional habits

Youthful

! Good– Coordination

– Musculature

– Adaptibiliy

! Challenge– Esthetics

– Demanding

! Select anatomic(cusped) posteriorteeth

Aged

! Helpful

– Experience

– Possible lowexpectation

– Esthetics

! Challenge

– Physical limitations

– Poor adaptability

! Select shallow cuspsor none at all unlessprevious denture iscusped

Patients with poor neuromuscular control

have difficulty accommodating to anatomic

occlusions. They are best served with

monoplane occlusal schemes.

Physical condition of the patient

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Complete Denture Occlusion

! Neuromuscular control and adaptabilitymay be the most significant factors in thesuccessful manipulation of completedentures under function

! Tongue function anddenture wearingexperience

Jaw Relationship

! A skeletal class II jaw relationship requiresa non-anatomic scheme due to the largeenvelope of motion.

! Skeletal class III patients chew verticallywith little anterior-posterior movement.Most schemes can be used.

! Crossbites generally require non-anatomicschemes.

If the present dentures have anatomic teeth

which have not been severely ground or worn

and the alveolar ridges are not severely

resorbed, anatomic teeth can be used. If the

existing denture teeth have been worn flat,

nonanatomic teeth may be a better choice.

Previous denture occlusion

Anxious, nervous individuals are more

apt to grind, which can be especially

traumatic to the supporting structures

when anatomic posterior denture teeth

are used. They are best served with

monoplane occlusal schemes.

Chronic bruxism

Mandibular Ridge Types Resorbed and/or movable ridges

Such conditions, as demonstrated in thesetwo patients, make it difficult to obtainaccurate intraoral records and permitmovement of the denture bases duringfunction. The poorer the record basestability, the less cusp height is indicated.

Exception: Some patients with highlyresorbed ridges retain superb tonguecontrol and a reasonably stable denturebase. If they are vertical chewers, ratherthan wide envelope grinders, they willprefer and be able to handle cusp fossateeth. Such patients are ideal candidatesfor lingualized occlusal schemes.

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• Many dentulous patients, especially those with

severely worn dentitions, have a discrepancy

between ICP (intercuspal position) and RCP

(retruded cuspal position).

• Removal of the natural teeth will permit and

encourage a retrusive shift in mandibular posture.

A non-intercuspated denture tooth form like

lingualized or monoplane would give the “freedom”

for the patient to reestablish the correct maxillo-

mandibular relationship.

Immediate dentures

Posterior Tooth Forms

Anatomic Tooth Forms Nonanatomic Tooth Forms

Semi-anatomic Tooth FormsDenture Occlusion Options

anatomic

Semi-anatomic

Lingualized

(lingual contact)

non-anatomic

(balancing

ramp)

non-

anatomic

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Non-anatomic 10 degree

20 degree 22 degree

33 degree 40 degree

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Specifically designed teeth forlingualized occlusion

Lingual Bladed Teethor

Levin Blades

Non-anatomic variations

Anatomic teeth should be -

Exception: European concept of physiologiccentric (Vident)

Balanced articulation is the bilateral,simultaneous, anterior and posteriorocclusal contact of teeth in centric andeccentric positions.

Is “Balance” Necessary?

“Bolus in”

“Balance out”

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Tests of Balanced and Non-balancedOcclusions

Trapozzano, V. R.: JPD 10: 476-487, 1960.

1) No patient preference

2) Balanced slightly more efficient

3) Percentage of patients using eccentricmovements during mastication is small


“Simplification of Occlusion in CompleteDenture Practice: Posterior Tooth Form

and Clinical Procedures”

Dale Smith: DCNA 14: No. 3; July, 1970.

1) Advocates cuspless teeth primarily forease of use

2) May use balanced occlusion but can’tprove that it is necessary

Balance and the Monoplane Occlusion

Minimize vertical overlap within the

dictates of esthetics and phonetics

Balance and Monoplane Occlusion

Minimize vertical overlap within the

dictates of esthetics and phonetics

Lingualized Occlusion

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Theoretically, there should beless lateral displacement of thedenture and less lateral forcesduring function when using

lingualized posterior dentureteeth.


The lingual cusp tips

should be in contact with

the central fossae of the

opposing mandibular

teeth. The cuspal

inclines of the mandibular

teeth are relatively flat,

resulting in potentially

less lateral forces and

displacement during

function.

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! Good esthetics

! Freedom of non-anatomic teeth

! Potential for bilateral balance

! Centralizes vertical forces

! Minimizes tipping forces

! Facilitates bolus penetration(mortar and pestle effect)

! High esthetic demands

! Displaceable supporting tissues

! Weak muscles of mastication

! Previous successful denture withLingualized Occlusion

Indications for use Advantages


• Good residual ridges

• Well coordinated patient

• Previously successful withanatomic dentures

• Denture opposes naturaldentition

• When cusp penetration ofbolus is desired

• Poor residual ridges

• Poor neuromuscular control(bruxers, CP etc.)

• Previously successful withmonoplane dentures orSeverely worn occlusion onprevious denture

• Arch discrepancies

• class II or III or cross-bite

• Immediate dentures

• except when opposingnatural dentition

• Potential poor follow-up

Non-anatomic Anatomic

Indications

• No vertical component to

aid in shearing duringmastication

• Patients may complain oflack of positiveintercuspation position?

• Somewhat estheticallylimited (don’t look likenatural teeth)

• Reduction of horizontal forces

• CR can be developed as anarea instead of a point

• Freedom of movement

• Can develop solid occlusion

despite arch alignmentdiscrepancies

• Easily adapted to situationsprone to denture base shifting

• Easy to set and adjust teeth

Advantages Disadvantages

Non-anatomic (monoplane occlusion)

• Difficult to set

• Less adaptable to archrelation discrepancies

• Horizontal forcedevelopment due to cuspinclinations

• Harmonious balancedocclusion is lost withdenture base settling

• Requires frequent follow-up and may require morefrequent relines tomaintain proper occlusion

• Intercuspation may bedeveloped

• Esthetically similar tonatural dentition

• Balanced occlusion can beachieved

• Maintains some shearingability after moderate wear

Advantages Disadvantages

Anatomic/semi-anatomic

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Credits:

UCLA School of Dentistry

American College of Prosthodontists

Dr. Gary Cook

posterior schemes

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