posterior schemes
TRANSCRIPT
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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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Is “Balance” Necessary?
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
Is “Balance” Necessary?
“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.
Lingualized Occlusion
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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Lingualized Occlusion
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7-18"#$26"*)
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Lingualized Occlusion
! 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
Lingualized Occlusion
• 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