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7/30/2019 8 -Fundamentals of Occlusion
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Fundamentals ofocclusion
Reference: ShillingburgFunamentals of Fixed
Prosthodontics, third editionchapter two
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Objective
Appreciate the importance of occlusion
The ability to diagnose and treat simple occlusaldisharmonies
To produce restorations that will avoid the creation of
iatrogenic disease
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Centric Relation The maxillomandibular relationship in which the condyles articulate with the
thinnest avascular portion of their respective disks with the complex in theanterior-superior position against the shapes of the articular eminencies. Thisposition is independent of tooth contact. This position is clinically discernible
when the mandible is directed superior and anteriorly. It is restricted to a purely
rotary movement about the transverse horizontal axis (GPT-5)
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Only hinge rotationmovement of the condyletakes place in centricrelation position
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Inter-cuspal position (ICP)Also called maximum intercuspation MIC
The position of maximum intercuspation betweenteeth
The most cranial position of the mandible
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Maximum Intercuspation
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Mandibular MovementSeries of motions occurring around three axes:
Horizontal axis
Vertical axis Sagittal axis
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Horizontal Axis
This Movement in the sagittal plane, happens when themandible in centric relation makes a purely rotationalopening and closing border movement around theterminal hinge axis
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Purehingerotation
translation
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Vertical Axis
This movement occurs in the horizontal plane whenthe mandible moves into a lateral excursion.
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Sagittal Axis
This movement occurs in the frontal plane during alateral excursion around an anteroposterior axis
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Protrusion
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Laterotrusion and mediotrusion Condyle in non working
Side moves forward
and medially Condyle in working
Side moves laterally
And Slightly posteriorly
WorkingsideNon Workingside
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Bennett angleThe angle formed in the horizontal plane, between the
pathway of the non working condyle in a mandibularlateral translation, and the sagittal plane.
NWS
NWS WS
WS
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Bennett
angleBennett
movement
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The determinants of mandibularmovement
Contacting teethTwo condyles
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The determinants of mandibular
movements Two condyles: Condylar guidance,Bennett angle (the
dentist has no control over the posterior
determinants.)
Contacting teeth: posterior and anterior teeth
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Condylar guidance
The angle formed in the sagittal plane, between the condylarpath during protrusion, and the horizontal plane
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Contacting teeth
Posterior teeth: Provide vertical stops for mandible closure
Guide the mandible into the position of maximumintercuspation
Anterior teeth: Guide the mandible into right and left lateral excursive
movement.
Guide the mandible in the protrusion movement.
Why are the anterior teeth more suitable to carry theguidance in excursions??
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During protrusive movement of the mandible , the incisaledges of the mandibular anterior teeth move forward anddownward along the lingual concavities of the maxillaryanterior teeth
Anterior guidance
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Anterior guidance The track of the incisal edges from max.
intercuspation to edge-to-edge
occlusion is called the protrusive incisalpath
The angle formed between theprotrusive incisal path and thehorizontal reference plane is called theprotrusive incisal path inclination
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In a healthy occlusion, the anterior guidance is 5 to 10degrees steeper than the condylar guidance
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Affect occlusal surface morphology of the posterior teeth:
Vertical overlap
Horizontal overlap
Anterior guidance
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One of the objectives of restorative dentistry is to placethe teeth in harmony with TMJ. This will result in min.stress on the teeth and joint
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Interferences
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Occlusal interferences
Contacts that may produce mandibulardeviation during closure to maximumintercuspation or may hinder smooth passage to
and from the intercuspal position:1. Centric
2. Working
3. Non-working4. Protrusive
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1.Centric interference
Premature contact that occurs when the mandiblecloses with the condyles in their optimum position inthe glenoid fossae
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2.working interferenceAn occlusal contact between the maxillary and
mandibular posterior teeth on the same side of thearches as the direction in which the mandible has
moved
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3.nonworking interference
An occlusal contact between maxillary and mandibularteeth on the side of arches opposite to the direction in
which the mandible has moved
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Consequences of pathologic occlusion Trauma to TMJ
Parafunctional jaw activities (bruxism andclenching)
Muscle fatigue or spasm
Facets and wear of teeth
Teeth mobility
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Optimum occlusion
Minimum adaptation by the patient
Criteria for optimum occlusion
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Organisation of the occlusion
Bilateral balanced occlusion
Unilateral balanced occlusion
Mutually protected occlusion
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Bilateral balanced occlusion Prosthetic concept : (not frequently used)
max. number of teeth contact in all excursivepositions of the mandible
useful in complete denture construction
in which contact on the non working side is needed
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Unilateral balanced occlusion Commonly known as group function :
(Widely used)
working side : all teeth are in contact
nonworking side : teeth are free of any
contact
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Unilaterally balanced occlusion Contacts betweenopposing posteriorteeth on the working
side only duringlateral excursion(group function lateralguidance)
Incisors and caninescarry the protrusiveguidance
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Mutually protected occlusion
Also known as canine protected occlusion:
ease of fabrication, greater tolerance by patients
anterior teeth protecting the posterior teeth in
mandibular excursions
post. teeth protecting anterior teeth at the intercuspal
position
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Mutually protected occlusion
- Posterior teethcome in contact onlyin intercuspalposition acting asvertical stops
- Canines on theworking side carrythe lateral guidance
- Incisors and caninescarry protrusiveguidance
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Thats it
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