Impressions / implant dentistry course

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IMPRESSIONS INIMPRESSIONS IN
COMPLETE DENTURESCOMPLETE DENTURES
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.comwww.indiandentalacademy.com

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INTRODUCTIONINTRODUCTION
An 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.

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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 used

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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 Impression
First proposed byFirst proposed by RichardsonRichardson and later popularised byand later popularised by
Harry PageHarry Page..
The impression is made with the oral mucous membraneThe impression is made with the oral mucous membrane
and the jaws in a normal, relaxed condition. Borderand 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 isThe mucostatic technique results in a denture, which is
closely adapted to the mucosa of the denturebearingclosely adapted to the mucosa of the denturebearing
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 displacedRecords the oral tissues in a functional and displaced
form. The materials used for this technique includeform. 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 returnThe 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 displacedDentures made by this technique tend to get displaced
due to the tissue rebound at rest. During function, thedue to the tissue rebound at rest. During function, the
constant pressure exerted onto the soft tissues limit theconstant pressure exerted onto the soft tissues limit the
blood circulation leading to residual ridge resorption.blood circulation leading to residual ridge resorption.

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Selective Pressure ImpressionSelective Pressure Impression
(Boucher)(Boucher)
In this technique, the impression is made to extend overIn this technique, the impression is made to extend over
as much denture-bearing area as possible withoutas much denture-bearing area as possible without
interfering with the limiting structures at function andinterfering with the limiting structures at function and
rest.rest.
The selective pressure technique makes it possible toThe 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 thebearing areas. This is achieved through the design of the
special tray in which the non stress-bearing areas arespecial tray in which the non stress-bearing areas are
relieved and the stress-bearing areas are allowed to comerelieved 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 IMPRESSION
The negative replica of the oral tissues used toThe negative replica of the oral tissues used to
prepare a diagnostic cast.prepare a diagnostic cast.
Used for study purposes like measuring theUsed 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 toIs 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 andArticulate 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 ofAn 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 clearanceThere 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 andThe tray should extend over hamular notch and
maxillary tuberosity. Mandibular tray shouldmaxillary 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)

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OBJECTIVES OF IMPRESSIONOBJECTIVES 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 prosthesisThat quality inherent in the prosthesis
which resists the force of gravity,which resists the force of gravity,
adhesiveness of foods, and the forcesadhesiveness of foods, and the forces
associated with the opening of the jaws.associated with the opening of the jaws.
(GPT)(GPT)

1919
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 sealAtmospheric 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 retentiveThe 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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STABILITYSTABILITY
The quality of a denture to be firm, steady,The quality of a denture to be firm, steady,
or constant, to resist displacement byor constant, to resist displacement by
functional stresses and not to be subject tofunctional 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 withstandIt is the ability of the denture to withstand
horizontal forces.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 ofThe resistance to vertical forces of
mastication, occlusal forces and othermastication, occlusal forces and other
forces applied in a direction towardsforces applied in a direction towards
the denture-bearing area.the denture-bearing area.

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 The denture base should cover asThe denture base should cover as
much denture-bearing area as possiblemuch 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 tostress-bearing areas will aid to
improve supportimprove support
SUPPORTSUPPORT

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AESTHETICSAESTHETICS
 The thickness of the denture flanges is one ofThe 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 labialterm edentulous patients to give required labial
fullness.fullness.
 Impression should perfectly reproduce the widthImpression should perfectly reproduce the width
and height of the entire sulcus for the properand height of the entire sulcus for the proper
fabrication of the flanges.fabrication of the flanges.

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PRESERVATION OF REMAININGPRESERVATION OF REMAINING
STRUCTURESSTRUCTURES
 De Van (1952) stated that, “the preservation ofDe Van (1952) stated that, “the preservation of
that which remains is of utmost importancethat which remains is of utmost importance
and not the meticulous replacement of thatand not the meticulous replacement of that
which has been lost.which has been lost.
 Impressions should record the details of theImpressions should record the details of the
basal seat and peripheral structures in anbasal seat and peripheral structures in an
appropriate form to prevent injury to the oralappropriate form to prevent injury to the oral
tissues.tissues.

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THANK YOUTHANK YOU
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Impressions / implant dentistry course

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