Impressions / implant dentistry course

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IMPRESSIONS IN IMPRESSIONS IN COMPLETE DENTURESCOMPLETE DENTURES

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.comwww.indiandentalacademy.com

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INTRODUCTIONINTRODUCTIONAn impression is defined as, "an imprint or nega

tive likeness of the teeth and/or edentulous areas where

the teeth have been removed, made in a plastic material

which becomes relatively hard or set while in contact

with these tissues. Impressions may be made of full

complements of teeth, of areas where some teeth have

been removed, or in mouth from which all teeth have

been removed" - GPT.www.indiandentalacademy.comwww.indiandentalacademy.com

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Complete denture impression is a

negative registration of the entire denture

bearing, stabilizing and border seal areas

present in the edentulous mouth. - GPT.


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Impressions are made to produce a

negative replica of the patient's mouth into

which plaster or stone can be poured to form

the positive replica- the cast. The cast acts

as a template over which the CD is

fabricated.


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CLASSIFICATIONCLASSIFICATION

1) Depending on the theories of impression

making.

2) Depending on the technique

3) Depending on the tray type

4) Depending on the purpose of the impression

5) Depending on the material usedwww.indiandentalacademy.comwww.indiandentalacademy.com

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Depending on theories of impression making

Mucostatic. Mucostatic.

Mucocompressive.Mucocompressive.

Selective pressure. Selective pressure.


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Mucostatic or Passive ImpressionMucostatic or Passive ImpressionFirst proposed by First proposed by RichardsonRichardson and later popularised by and later popularised by

Harry PageHarry Page. . The impression is made with the oral mucous membrane The impression is made with the oral mucous membrane

and the jaws in a normal, relaxed condition. Border and the jaws in a normal, relaxed condition. Border moulding is not done here.moulding is not done here.

The impression is made with an oversized traThe impression is made with an oversized tra Impression material of choice is impression plaster. Impression material of choice is impression plaster. Retention is mainly due to interfacial surface tension. Retention is mainly due to interfacial surface tension.

The mucostatic technique results in a denture, which is The mucostatic technique results in a denture, which is closely adapted to the mucosa of the denture-bearing closely adapted to the mucosa of the denture-bearing area but has poor peripheral seal.area but has poor peripheral seal.


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Mucocompressive ImpressionMucocompressive Impression (Carole Jones)(Carole Jones)

Records the oral tissues in a functional and displaced Records the oral tissues in a functional and displaced

form. The materials used for this technique include form. The materials used for this technique include

impression compound, waxes and soft liners.impression compound, waxes and soft liners.

The oral soft tissues are resilient and thus tend to return The oral soft tissues are resilient and thus tend to return

to their anatomical position once the forces are relieved. to their anatomical position once the forces are relieved.

Dentures made by this technique tend to get displaced Dentures made by this technique tend to get displaced

due to the tissue rebound at rest. During function, the due to the tissue rebound at rest. During function, the

constant pressure exerted onto the soft tissues limit the constant pressure exerted onto the soft tissues limit the

blood circulation leading to residual ridge resorption.blood circulation leading to residual ridge resorption.www.indiandentalacademy.comwww.indiandentalacademy.com

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Selective Pressure ImpressionSelective Pressure Impression (Boucher)(Boucher)

In this technique, the impression is made to extend over In this technique, the impression is made to extend over

as much denture-bearing area as possible without as much denture-bearing area as possible without

interfering with the limiting structures at function and interfering with the limiting structures at function and

rest.rest.

The selective pressure technique makes it possible to The selective pressure technique makes it possible to

confine the forces acting on the denture to the stress-confine the forces acting on the denture to the stress-

bearing areas. This is achieved through the design of the bearing areas. This is achieved through the design of the

special tray in which the non stress-bearing areas are special tray in which the non stress-bearing areas are

relieved and the stress-bearing areas are allowed to come relieved and the stress-bearing areas are allowed to come

in contact with the tray. in contact with the tray. www.indiandentalacademy.comwww.indiandentalacademy.com

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Depending on the technique

Open-mouthOpen-mouth

Closed-mouthClosed-mouth


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Depending on the tray type

Stock trayStock tray

Custom trayCustom tray


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Depending on the purpose of the impression

DiagnosticDiagnostic

PrimaryPrimary

SecondarySecondary


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DIAGNOSTIC IMPRESSIONDIAGNOSTIC IMPRESSIONThe negative replica of the oral tissues used to The negative replica of the oral tissues used to

prepare a diagnostic cast.prepare a diagnostic cast.

Used for study purposes like measuring the Used for study purposes like measuring the

undercuts, locating the path of insertion.undercuts, locating the path of insertion.

Is made as a part of treatment plan and to Is made as a part of treatment plan and to

estimate the amount of pre-prosthetic surgery.estimate the amount of pre-prosthetic surgery.

Articulate the casts on tentative jaw relation and Articulate the casts on tentative jaw relation and

evaluate the inter-arch spaceevaluate the inter-arch spacewww.indiandentalacademy.comwww.indiandentalacademy.com

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PRIMARY IMPRESSIONPRIMARY IMPRESSION(PRELIMINARY IMPRESSION)(PRELIMINARY IMPRESSION)

An impression made for the purpose of An impression made for the purpose of diagnosis or for the construction of a tray.diagnosis or for the construction of a tray.

There should be at least 5mm clearance There should be at least 5mm clearance between the stock tray and the ridge.between the stock tray and the ridge.

The tray should extend over hamular notch and The tray should extend over hamular notch and maxillary tuberosity. Mandibular tray should maxillary tuberosity. Mandibular tray should cover retromolar pad.cover retromolar pad.

Tray can be extended using modelling wax.Tray can be extended using modelling wax.

Impression compound, Alginate, Impression plasterwww.indiandentalacademy.comwww.indiandentalacademy.com

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SECONDARY IMPRESSIONSECONDARY IMPRESSION(WASH IMPRESSION)(WASH IMPRESSION)

Involve: Involve: Fabriction of custom tray.Fabriction of custom tray.Border molding.Border molding.Developing the posterior palatal seal.Developing the posterior palatal seal.Making the wash impressionMaking the wash impression..


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Depending on the material usedDepending on the material used

Reversible hydrocolloid impression.Reversible hydrocolloid impression.

Irreversible hydrocolloid impression.Irreversible hydrocolloid impression.

Modeling plastic impression. Modeling plastic impression.

Plaster impression.Plaster impression.

Wax impression.Wax impression.

Silicone impression.Silicone impression.

Thiokol rubber impression. (Polysulphide)Thiokol rubber impression. (Polysulphide)www.indiandentalacademy.comwww.indiandentalacademy.com

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OBJECTIVES OF IMPRESSION OBJECTIVES OF IMPRESSION MAKINGMAKING

1)1) RetentionRetention

2)2) StabilityStability

3)3) SupportSupport

4)4) AestheticsAesthetics

5)5) Preservation of remaining structuresPreservation of remaining structures


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RETENTIONRETENTION

That quality inherent in the prosthesis That quality inherent in the prosthesis

which resists the force of gravity, which resists the force of gravity,

adhesiveness of foods, and the forces adhesiveness of foods, and the forces

associated with the opening of the jaws. associated with the opening of the jaws.

(GPT)(GPT)


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Factors affecting RetentionFactors affecting Retention

Anatomical factorsAnatomical factors Physiological factorsPhysiological factors Physical factorsPhysical factors Mechanical factorsMechanical factors Muscular factorsMuscular factors


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Anatomical factorsAnatomical factors

Size of the denture bearing areaSize of the denture bearing area

Quality of the denture bearing area.Quality of the denture bearing area.



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Physiological factorsPhysiological factors

Saliva and its qualitySaliva and its quality



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Physical factorsPhysical factors AdhesionAdhesion CohesionCohesion Interfacial surface tensionInterfacial surface tension Capallarity and capillary attractionCapallarity and capillary attraction Atmospheric pressure and peripheral seal Atmospheric pressure and peripheral seal



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Mechanical factorsMechanical factors UndercutsUndercuts Retentive springsRetentive springs Magnetic forcesMagnetic forces Denture adhesiveDenture adhesive Suction chambers and suction discsSuction chambers and suction discs



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Muscular factorsMuscular factors The muscles apply supplementary retentive The muscles apply supplementary retentive

forces on the denture.forces on the denture.

It is most effective in the neutral zone. It is most effective in the neutral zone.



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STABILITYSTABILITYThe quality of a denture to be firm, The quality of a denture to be firm,

steady, or constant, to resist displacement by steady, or constant, to resist displacement by functional stresses and not to be subject to functional stresses and not to be subject to change of position when force is applied.change of position when force is applied.

It is the ability of the denture to It is the ability of the denture to withstand horizontal forces. withstand horizontal forces.


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Vertical height of the residual ridge.Vertical height of the residual ridge.

Quality of soft tissue covering the ridge.Quality of soft tissue covering the ridge.

Occlusal planeOcclusal plane

Quality of the impression.Quality of the impression.

Teeth arrangement.Teeth arrangement.

Contour of the polished surfaces. Contour of the polished surfaces.

FACTORS AFECTING STABILITYFACTORS AFECTING STABILITY


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SUPPORTSUPPORT

The resistance to vertical forces of The resistance to vertical forces of

mastication, occlusal forces and other mastication, occlusal forces and other

forces applied in a direction towards forces applied in a direction towards

the denture-bearing area.the denture-bearing area.


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The denture base should cover as The denture base should cover as

much denture-bearing area as possible much denture-bearing area as possible

to provide good support.to provide good support.

Confining the occlusal forces to stress-Confining the occlusal forces to stress-

bearing area and reliving the non-bearing area and reliving the non-

stress-bearing areas will aid to stress-bearing areas will aid to

improve support improve support

SUPPORTSUPPORT


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AESTHETICSAESTHETICS The thickness of the denture flanges is one of The thickness of the denture flanges is one of

the important factors that govern esthetics.the important factors that govern esthetics.

Thicker denture flanges are preferred in long-Thicker denture flanges are preferred in long-

term edentulous patients to give required labial term edentulous patients to give required labial

fullness.fullness.

Impression should perfectly reproduce the width Impression should perfectly reproduce the width

and height of the entire sulcus for the proper and height of the entire sulcus for the proper

fabrication of the flanges. fabrication of the flanges. www.indiandentalacademy.comwww.indiandentalacademy.com

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PRESERVATION OF REMAINING PRESERVATION OF REMAINING STRUCTURESSTRUCTURES

De Van (1952) stated that, “the preservation of De Van (1952) stated that, “the preservation of that which remains is of utmost importance that which remains is of utmost importance and not the meticulous replacement of that and not the meticulous replacement of that which has been lost.which has been lost.

Impressions should record the details of the Impressions should record the details of the basal seat and peripheral structures in an basal seat and peripheral structures in an appropriate form to prevent injury to the oral appropriate form to prevent injury to the oral tissues.tissues.


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