Principles of complete Principles of complete denturedenture

Lecturer Lecturer

Hatem Dousouky AhmadHatem Dousouky Ahmad

Lecture out lineLecture out line

1.1. Steps of complete denture construction.Steps of complete denture construction.

2.2. Indications and contra indications of Indications and contra indications of complete dentures.complete dentures.

3.3. Difference between natural and denture Difference between natural and denture teeth.teeth.

4.4. Retention in complete dentures.Retention in complete dentures.

5.5. Support in complete dentures.Support in complete dentures.

6.6. Stability in complete dentures.Stability in complete dentures.

11--Steps of complete denture Steps of complete denture constructionconstruction..

2- indications and contraindication 2- indications and contraindication of complete denturesof complete dentures

Indications:Indications:

All edentulous arches are All edentulous arches are indicated for complete indicated for complete dentures unless there dentures unless there is a temporary or a is a temporary or a permanent reason permanent reason preventing the preventing the treatmenttreatment

Contra indications:Contra indications: Temporary factors:Temporary factors:

1)1) Remaining roots or Remaining roots or teeth.teeth.

2)2) Local pathos's as cysts.Local pathos's as cysts.

3)3) Overwhelming disease.Overwhelming disease.

Permanent contraindications:1)Epileptic patients and other psychological disorders preventing the neuromuscular control over the denture to avoid suffocation.

33 - -difference between natural and difference between natural and artificial teethartificial teeth..

Natural teethNatural teeth Denture teethDenture teeth

Quality of complete dentureQuality of complete denture

A denture is said to be successful when it is:1)Stable in place at function and rest.2)Performs it’s masticatory and esthetic functions.3)Preserves the foundation tissues.

I- Tissue-ward movementsI- Tissue-ward movements

II- Tissue-away movementsII- Tissue-away movements

III- Horizontal movementsIII- Horizontal movements:: A) Lateral movementsA) Lateral movements

B) Antero-posterior B) Antero-posterior movementsmovements..

IV- Rotational movementsIV- Rotational movements

At least four possible movements of the dentures exist

General movements of the General movements of the denturedenture

Direction of movement

Cause of movementResisted by

Tissue away movement

Sticky foodGravity in upper

denture

Retention

Tissue ward movement

Mastication.support

Rotational movementChewing on one sidestability

Horizontal movement:A- antro-posterior.B-medio-lateral.

Chewing, clenching,side to side

movement, muscleeffect

bracing

•Mastication, Swallowing And Aimless

Tooth Contact. Biting Forces

I- Tissue-ward movements

•C.D. should be designed to resist this movement by providing adequate

supporting from the foundation tissues

•This function of the complete denture is

called “Support”

• It is the Resistance to Tissue Ward Movement

1-Support

• Obtained by adequate Distribution of Forces Over the Supporting Sttructures.

• The quality of the denture to transfer Occlusal Stresses to the Supporting Oral Structures and decrease forces / unit area

•Adequate Distribution of Forces Over the Supporting Sttructure

•Decrease forces/unit area

•The Resistance to Tissue Ward Movement

Tissue-away forces occur due to

The action of muscles acting along the periphery of the denture

•This function of the complete denture is

called “Retention”

Gravity acting on upper dentures or by

sticky food adhering to the artificial teeth or to the denture base.

1-Adhesion 2-Cohesion

4-Interfacial s.t.*Viscosity (interfacial

viscous tension)

4-At. pressure 5-Gravity

MechanicalMechanical

2-Retention

PhysiologicalPhysiologicalPhysical

• Physical condition•The physiologic molding of

the tissues around the polished surfaces

• neuromuscular control• Degree of tissue tone• Quality and quantity of

saliva• Condition of mucosa and

submucosa• Ridge characteristics

• Ridge relationship

•Parts of the denture engaging tissue undercuts.

•Occlusion•Leverage•Contour of

denture bases

3- Bracing3- BracingHorizontal movementsHorizontal movements

Horizontal forces developed when the mandible moves from side to side

during function while the teeth are in contact

Lateral movements have a

destructive effect

This Function Is Mainly Provided By:

Adequate extension of the flanges

4-Stabilization

Is the Resistance of the Denture

to rotational forces (Tipping -

Rocking)

1-Adhesion 2-Cohesion

4-Interfacial s.t.*Viscosity (interfacial

viscous tension)

4-At. pressure 5-Gravity

MechanicalMechanical

2-Retention

PhysiologicalPhysiologicalPhysical

• Physical condition•The physiologic molding of

the tissues around the polished surfaces

• neuromuscular control• Degree of tissue tone• Quality and quantity of

saliva• Condition of mucosa and

submucosa• Ridge characteristics

• Ridge relationship

•Parts of the denture engaging tissue undercuts.

•Occlusion•Leverage•Contour of

denture bases

11--Physiologic factorsPhysiologic factors

1.1. Physical condition of the tissues and the patient(the Physical condition of the tissues and the patient(the

better the physical condition the better is the better the physical condition the better is the

retention.retention.

2.2. Degree of tissue toneDegree of tissue tone

3.3. Quality and quantity of salivaQuality and quantity of saliva

4.4. Condition of mucosa and submucosaCondition of mucosa and submucosa

5.5. Neuromuscular controlNeuromuscular control

6.6. Ridge characteristicsRidge characteristics

7.7. Ridge relationshipRidge relationship

PhysiologicalPhysiological

Oral And Facial MusculatureOral And Facial Musculature

The Polished Surfaces Are Properly The Polished Surfaces Are Properly ShapedShaped , ,

The Teeth Are Positioned In The The Teeth Are Positioned In The Neutral Zone AndNeutral Zone And

The Denture Bases Are Properly The Denture Bases Are Properly Extended To Cover The Maximum Area Extended To Cover The Maximum Area PossiblePossible , ,

Muscular control is an important aspect of successful complete denture therapy. providing that :

The Polished Surface The Polished Surface ContourContour

22--Physical factorsPhysical factors

1-Adhesion 2-Cohesion

4-Interfacial s.t.*Viscosity (interfacial

viscous tension)

4-At. pressure 5-Gravity

MechanicalMechanical

2-Retention

PhysiologicalPhysiologicalPhysical

• Physical condition•The physiologic molding of

the tissues around the polished surfaces

• neuromuscular control• Degree of tissue tone• Quality and quantity of

saliva• Condition of mucosa and

submucosa• Ridge characteristics

• Ridge relationship

•Parts of the denture engaging tissue undercuts.

•Occlusion•Leverage•Contour of

denture bases

Adhesion and Adhesion and

CohesionCohesion

Adhesive failure refers to the interface between two

bodies; cohesive failure to within a material itself .

Note: the cohesive strength of saliva is much greater than

the adhesion of mucosa to PMMA

AdhesionAdhesion AAdhesion of saliva to the mucous dhesion of saliva to the mucous

membranemembrane and the denture base is achieved and the denture base is achieved

through through ionic forces between charged ionic forces between charged

salivary glycoprotein and surface salivary glycoprotein and surface

epithelium epithelium

CohesionCohesionPhysical attraction of like molecules for each otherPhysical attraction of like molecules for each other

creates retentive force and usually occurs with creates retentive force and usually occurs with

saliva that is present between the denture base and saliva that is present between the denture base and

the mucosathe mucosa . .

Normal salivaNormal saliva is not very cohesive, and unless the is not very cohesive, and unless the

interposed saliva is modified with the use of denture interposed saliva is modified with the use of denture

adhesive, retentive force cannot be achievedadhesive, retentive force cannot be achieved..

Retention supplied by Retention supplied by Adhesion depend onAdhesion depend on: :

1)1) The area covered by the dentureThe area covered by the denture

2)2) the close adaptation of the the close adaptation of the

denture to the supporting tissuesdenture to the supporting tissues

3)3) The fluidity of salivaThe fluidity of saliva

Atmospheric pressureAtmospheric pressure

If The Dentures Have If The Dentures Have An Effective SealAn Effective Seal

Around Their Borders. Around Their Borders. This Is Called This Is Called

‘Suction’‘Suction’ Because It Is The Resistance To Because It Is The Resistance To

Removal In A Direction Opposite To That Removal In A Direction Opposite To That

Of Insertion. But Of Insertion. But There Is No Suction Or There Is No Suction Or

Negative Pressure, Except When Negative Pressure, Except When

Another Force Is AppliedAnother Force Is Applied

Displacement of a sealed bellows-like device results in a vacuum in the emergent space, the displacing force being

balanced by that from atmospheric pressure. There is no static retaining force otherwise. Comparable conditions

are unlikely to occur in the mouth

Atmospheric pressure

All valve and suction retention systems are similar: a

spring of some description attempts to maintain a region

of lowered pressure.

These all fail to be effective in the long run for

physiological reasons

vacuum

For atmospheric pressure to For atmospheric pressure to

be effective, the denture be effective, the denture

must havemust have

a perfect seala perfect seal around its around its

entire borderentire border

Interfacial Surface Interfacial Surface TensionTension

It is attributed to the It is attributed to the

attractive forces or attractive forces or

cohesion of the surface cohesion of the surface

molecules of the liquidmolecules of the liquid..

Interfacial Surface Interfacial Surface TensionTension

Is A Resistance To Separation By The

Film Of Liquid Between The Denture

Base And Supporting Tissues .

It Combines The Actions Of Adhesion

And Cohesion And Is Similar To

Capillary Attraction.

Bulging liquid surfaces imply a Bulging liquid surfaces imply a higher pressure within the liquid; higher pressure within the liquid;

incurving surfaces imply a lowered incurving surfaces imply a lowered

pressurepressure

Surface tension

•When is interfacial surface tension most effective ?

•When the salivary film is very thin,

there is a perfect adaptation of the

denture base and the soft tissues are

firmly attached to underlying bone and

not distorted.

What effect does distance between the

denture base and the mucous membrane

have on retention and what is it called ?

"Capillary attraction"

Simplified

cross-section

to illustrate

the seal

arising from

compliant

tissue, flow

restriction in

narrow spaces,

and the effect

of surface

tension in a

well-fitting

denture

ViscosityViscosityIt is the resistance by one part of A liquid in moving over It is the resistance by one part of A liquid in moving over

another partanother part..The rate of separationThe rate of separation of two surfaces under an applied of two surfaces under an applied

forceforce,,Very Very thin watery salivathin watery saliva does not seal the denture well and does not seal the denture well and

the seal can be easily brokenthe seal can be easily broken..The need for a The need for a good base adaptationgood base adaptation to the tissues to the tissues

Full surface Full surface area coveredarea covered by the denture. This may be by the denture. This may be

relevant to the maxillary denturerelevant to the maxillary denture . .The mandibular denture are bathed in salivaThe mandibular denture are bathed in saliva, surface , surface

tension, viscosity and film thickness may not play a role in tension, viscosity and film thickness may not play a role in

lower denture retentionlower denture retention

Gravity•The weight of a lower prosthesis

constitutes a negligible gravitational force and is insignificant in comparison with the other forces acting on a denture .

•this may be beneficial in cases where other retentive forces and factors are marginal.

Base AdaptationBase Adaptation

the narrowness of the gap the narrowness of the gap

contributes a retentive force contributes a retentive force

through the effects of surface through the effects of surface

tension, via the curvature that tension, via the curvature that

results in the liquid surfaceresults in the liquid surface

Border sealBorder sealAttention was drawn under 'Surface Tension' to the fact that along most of the border of a denture there is double contact of acrylic and soft tissue such that displacing the denture in the separation sense does not open a gap along that border

Soft tissue

Denture retention is therefore a dynamic issue as it mostly depends on factors controlling the flow of the interposed fluid .

The better the fit to the tissue, and the better the linear extent of the seal at the border, the better the denture will resist short term displacing forces.

Ultimately, the central factors for

the success of a denture depend

primarily on the quality of the fit of

the denture to soft tissue. This in

turn hinges on the impression

technique and subsequent denture

base design and fabrication

1. Have less surface area.

2. Are bathed in saliva.

The effect of physical forces is less applicable to lower

dentures than upper because:

3. Strong movements of the tongue

This Function Is Mainly Provided By:

1-Mechanical -- Undercuts

2 -physiologic forces on polished surfaces of denture bases

3 -physical forces on fitting surfaces of denture

bases

Thank youThank you