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Impression techniquesImpression techniques
in complete denturesin complete dentures..
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Table of contentsTable of contents
IntroductionIntroduction
DefinitionsDefinitions
historyhistory
Review of literatureReview of literature
Principles of impression makingPrinciples of impression making
Theories of impression makingTheories of impression making

Impression techniques.Impression techniques.
-muco compressive technique .-muco compressive technique .
-muco static technique.-muco static technique.
-Selective pressure technique.-Selective pressure technique.
Preliminary impressions.Preliminary impressions.
Fabrication of custom tray.Fabrication of custom tray.
Border molding.Border molding.
Secondary impressions.Secondary impressions.

 Specialized impressionSpecialized impression
techniques.techniques.
 SummarySummary
 ConclusionsConclusions
 ReferencesReferences

Introduction.Introduction.
The impression appointment is theThe impression appointment is the
most important to the dentist and themost important to the dentist and the
patient for several reasons. It ispatient for several reasons. It is
usually the first prolongedusually the first prolonged
appointment following theappointment following the
examination and consultation withexamination and consultation with
the patient. Good impressions arethe patient. Good impressions are
basic to the needs of the contendedbasic to the needs of the contended
denture wearer.denture wearer.

The impression problem would notThe impression problem would not
be a problem if we take thebe a problem if we take the
impressions of the casts. Theimpressions of the casts. The
problem is due to the fact that theproblem is due to the fact that the
mouth is lined by the displaceablemouth is lined by the displaceable
tissue which varies in degree oftissue which varies in degree of
displacibility.displacibility.

In view of these facts , it isIn view of these facts , it is
reasonable to say that the idealreasonable to say that the ideal
impression must be in the mind ofimpression must be in the mind of
the dentist before it is in his hand.the dentist before it is in his hand.
He must literally make impressionHe must literally make impression
rather than take it. The kind ofrather than take it. The kind of
impression he will make dependsimpression he will make depends
on the factors which we shallon the factors which we shall
presently consider.presently consider.

Definitions:-Definitions:-
Impression:-A negative likeness orImpression:-A negative likeness or
copy in reverse of an object ; ancopy in reverse of an object ; an
imprint of the teeth and the adjacentimprint of the teeth and the adjacent
structures for use in dentistry.-GPT7.structures for use in dentistry.-GPT7.
A complete denture impression isA complete denture impression is
negetive registration of the entirenegetive registration of the entire
denture bearing, stabilizing anddenture bearing, stabilizing and
border seal areas present inborder seal areas present in
edentulous mouth (Heartwell)edentulous mouth (Heartwell)www.indiandentalacademy.comwww.indiandentalacademy.com

Impression Area:-The surfaceImpression Area:-The surface
recorded in an impression.-GPT7recorded in an impression.-GPT7

Impression Surface:-The portion ofImpression Surface:-The portion of
the denture surface that has itsthe denture surface that has its
contour determined by thecontour determined by the
impression.-GPT7impression.-GPT7
Impression tray:- GPT7Impression tray:- GPT7
1.A receptacle into which suitable1.A receptacle into which suitable
impression material is placed toimpression material is placed to
make the negative likeness.make the negative likeness.

2.a device used to carry , confine2.a device used to carry , confine
&control impression material&control impression material
while making an impression.while making an impression.
Preliminary impressions:-aPreliminary impressions:-a
negative likeness made for thenegative likeness made for the
purpose of diagnosis, treatmentpurpose of diagnosis, treatment
planning, or fabrication of the trayplanning, or fabrication of the tray
.GPT7.GPT7

Preliminary impression is anPreliminary impression is an
impression made for the purposeimpression made for the purpose
of diagnosis or for theof diagnosis or for the
construction of the tray.construction of the tray.
(Heartwell).(Heartwell).

1.the shaping of the border areas1.the shaping of the border areas
of the impression tray by functionalof the impression tray by functional
or manual manipulation of theor manual manipulation of the
tissue adjacent to the borders totissue adjacent to the borders to
duplicate the contour and size ofduplicate the contour and size of
the vestibule.the vestibule.
Border molding:-GPT7Border molding:-GPT7

2.determining the extension of the2.determining the extension of the
prosthesis by using tissueprosthesis by using tissue
function or manual manipulationfunction or manual manipulation
of the tissues to shape the borderof the tissues to shape the border
areas of the impression material.areas of the impression material.

Final impressions: a impressionFinal impressions: a impression
that represents the completion ofthat represents the completion of
the registration of the surface orthe registration of the surface or
the object.GPT7the object.GPT7
A final impression is a impressionA final impression is a impression
for making master casts.for making master casts.
(heartwell).(heartwell).

History of impressions.History of impressions.
1600- Prior to 1600 no complete1600- Prior to 1600 no complete
dentures were made due to lackdentures were made due to lack
of understanding of retention.of understanding of retention.
Replacements were made onlyReplacements were made only
when the posterior abutmentswhen the posterior abutments
were present.were present.
1711- Mathew Gottfried Purman1711- Mathew Gottfried Purman
recorded impression using wax.recorded impression using wax.www.indiandentalacademy.comwww.indiandentalacademy.com

1728: Pierre Fauchard made dentures1728: Pierre Fauchard made dentures
mesuring with compass and cutting bonemesuring with compass and cutting bone
into an appropriate shape to be filled.into an appropriate shape to be filled.
1845-18991845-1899
1848: Westcott, Dwinelle, Dunning1848: Westcott, Dwinelle, Dunning
introduced guttapercha. It was used as aintroduced guttapercha. It was used as a
impression material.impression material.
1884: Plaster of paris was first used as1884: Plaster of paris was first used as
Charles Stent introduced ImpressionCharles Stent introduced Impression
compoundcompound www.indiandentalacademy.comwww.indiandentalacademy.com

many changes became evident in thismany changes became evident in this
era. Till then only one impressionsera. Till then only one impressions
deemed sufficient.deemed sufficient.
It advanced to a method usingIt advanced to a method using
preliminary impressions.preliminary impressions.
This was followed by secondory washThis was followed by secondory wash
impression made of plaster withinimpression made of plaster within
preliminary impression.preliminary impression.

1900: Closed mouth impression1900: Closed mouth impression
procedure was introduced.procedure was introduced.
1900-1929: Several basic1900-1929: Several basic
principles of making impressionsprinciples of making impressions
were introduced. Advances inwere introduced. Advances in
accuracy of impression techniqueaccuracy of impression technique
and increase in the method ofand increase in the method of
border molding and obtainingborder molding and obtaining
peripheral seal were among theperipheral seal were among the
major advancesmajor advances

Green brothers introduced moco-Green brothers introduced moco-
compressive impressioncompressive impression
technique.technique.
Tyrde et al.,advocated the use ofTyrde et al.,advocated the use of
closed mouth technique.closed mouth technique.
1930-1950: several impression1930-1950: several impression
materials were introduced suchmaterials were introduced such
as reversible hydrocolloid ,zincas reversible hydrocolloid ,zinc
oxide and oil of cloves.oxide and oil of cloves.

1944: Addison described1944: Addison described
“mucostatic impression and“mucostatic impression and
attributed to Page.attributed to Page.
1950-1964: During this era there1950-1964: During this era there
was increased emphasis onwas increased emphasis on
biological factors of completebiological factors of complete
dentures.dentures.
Boucher proposed selectiveBoucher proposed selective
pressure technique in1951.pressure technique in1951.

1965-1980: newer techniques1965-1980: newer techniques
have been developed to managehave been developed to manage
poor mandibular ridges.poor mandibular ridges.
Tyrde and Robert introducedTyrde and Robert introduced
sublingual flange technique .sublingual flange technique .
Lott and Levin introduced flangeLott and Levin introduced flange
technique.technique.

Review of literature:Review of literature:
1.1. Charles H. Moses (1953):Charles H. Moses (1953):
physical considerations in impressionphysical considerations in impression
making. JPD 1953:3(4);449-62)making. JPD 1953:3(4);449-62)
He states that :He states that :
there must be no displacement ofthere must be no displacement of
tissues in so far as possible totissues in so far as possible to
avoid it.avoid it.

physical considerations in impressionphysical considerations in impression
making. JPD 1953:3(4);449-62)making. JPD 1953:3(4);449-62)
complete denture impressionscomplete denture impressions
.JPD1965:15;603-14..JPD1965:15;603-14.
 Posterior border seal – its rationale andPosterior border seal – its rationale and
importance.JPD1958:8;386-97importance.JPD1958:8;386-97

complete denture impressionscomplete denture impressions
.JPD1965:15;603-14.JPD1965:15;603-14

if displacement is necessary atif displacement is necessary at
the peripheral borders to takethe peripheral borders to take
advantage of atmosphericadvantage of atmospheric
pressure, the degree ofpressure, the degree of
displacement must be minimizeddisplacement must be minimized
so the elastic force is not greaterso the elastic force is not greater
than the retentive forcethan the retentive force

 there must be intimate contactthere must be intimate contact
between the denture base and thebetween the denture base and the
undisplaced tissues. this producesundisplaced tissues. this produces
thin film of saliva.thin film of saliva.
 physiologic seal areas arephysiologic seal areas are
advantageous because atmosphericadvantageous because atmospheric
pressure is an important adjunct topressure is an important adjunct to
denture retention.denture retention.
 ridge form is important retentiveridge form is important retentive
factor in denture retention.factor in denture retention.

 the area covered by the denturethe area covered by the denture
is a factor of retention. Theis a factor of retention. The
greator the area covered thegreator the area covered the
greater will be the retention.greater will be the retention.
 the viscosity of saliva is the factorthe viscosity of saliva is the factor
of retention.of retention.
 friction could be a factor, but it isfriction could be a factor, but it is
not recommended because of thenot recommended because of the
pathogenic conditions it induces.pathogenic conditions it induces.

Glen E. Tilton (1956):Glen E. Tilton (1956): AA
minimum pressure completeminimum pressure complete
denture impression techniquedenture impression technique
JPD1956:6(1);6-23JPD1956:6(1);6-23
States that: The pressure appliedStates that: The pressure applied
in impression making must bein impression making must be
equally balanced throught theequally balanced throught the
entire area of impression.entire area of impression.

The tissues of the mouth , or indeedThe tissues of the mouth , or indeed
any tissues of the body ,will notany tissues of the body ,will not
tolerate constant pressure withouttolerate constant pressure without
change; therefore, pressure on thechange; therefore, pressure on the
tissue in function beneath a denturetissue in function beneath a denture
must be momentry.must be momentry.
In his opinion , all denture-bearingIn his opinion , all denture-bearing
tissue will be at rest when thetissue will be at rest when the
mandible is in rest position.mandible is in rest position.

Irving R. Hardy (1958)Irving R. Hardy (1958) Posterior border sealPosterior border seal
– its rationale and importance.JPD1958:8;386-97.– its rationale and importance.JPD1958:8;386-97.
Said that the establishment of theSaid that the establishment of the
distal length of the basal seat anddistal length of the basal seat and
the development of the PPS is mostthe development of the PPS is most
important step in construction of theimportant step in construction of the
complete dentures. In addition tocomplete dentures. In addition to
providing retention recording PPSproviding retention recording PPS
has following advantages:-has following advantages:-

 it provides close contact of theit provides close contact of the
denture base with the mucousdenture base with the mucous
membrane which prevents foodmembrane which prevents food
getting under the tissue.getting under the tissue.
 it provides firm contact of theit provides firm contact of the
denture base with the tissue,denture base with the tissue,
and this diminishes or eliminatesand this diminishes or eliminates
gagginggagging

 it supplies sunken distalit supplies sunken distal
borders which is lessborders which is less
conspicuous to the tongue.conspicuous to the tongue.
 it provides a thick borders toit provides a thick borders to
counteract denture warpage.counteract denture warpage.


Henry A. Collett (1965);Henry A. Collett (1965);
complete denture impressionscomplete denture impressions
.JPD1965:15;603-14..JPD1965:15;603-14.
Told that the theories attemptingTold that the theories attempting
to explain the retention of theto explain the retention of the
denture seem to agree that closedenture seem to agree that close
adaptation of the denture basesadaptation of the denture bases
to the tissues is desirable , andto the tissues is desirable , and
the retention is proportianate tothe retention is proportianate to
the area coveredthe area covered

Displaced tissues have aDisplaced tissues have a
tendency to return to a positiontendency to return to a position
and form of equilibrium. Becauseand form of equilibrium. Because
of this , it seems to be desirableof this , it seems to be desirable
to have the patient either removeto have the patient either remove
his old dentures for a day or twohis old dentures for a day or two
or to have the tissue conditionedor to have the tissue conditioned
in other manner beforein other manner before
impressions.impressions.

Tissues that we displace whileTissues that we displace while
making impressions havemaking impressions have
tendency to return to theirtendency to return to their
original form due to resilienceoriginal form due to resilience
and they have tendency toand they have tendency to
displace the dentures. A borderdisplace the dentures. A border
seal should be created byseal should be created by
positive pressure. This will resultpositive pressure. This will result
in retention.in retention.

The selection of theThe selection of the
impression material orimpression material or
combination of materialcombination of material
should be determined by theshould be determined by the
objectives of the dentist andobjectives of the dentist and
the skill with which hethe skill with which he
manipulates the materialmanipulates the material


Gred Tryde et al (1965);Gred Tryde et al (1965); dynamicdynamic
impression techniques .JPD1965:15;1023-32.impression techniques .JPD1965:15;1023-32.
Described that dynamic impressionDescribed that dynamic impression
methods are the means ofmethods are the means of
overcoming treatment difficulties ofovercoming treatment difficulties of
patients with advanced mandibularpatients with advanced mandibular
ridge resorption.ridge resorption.
The advantages of dynamicThe advantages of dynamic
impression methods areimpression methods are

 avoidence of the dislocatingavoidence of the dislocating
effect of the muscles oneffect of the muscles on
improperly formed dentureimproperly formed denture
borders.borders.
 complete utilization of thecomplete utilization of the
possibilities of the passive andpossibilities of the passive and
active tissue fixation of theactive tissue fixation of the
dentures.dentures.

These advantages are the directThese advantages are the direct
result of the impression materialresult of the impression material
being shaped by the functionalbeing shaped by the functional
movements of the musclesmovements of the muscles
muscle attachments that bordermuscle attachments that border
the denture base.the denture base.

V . Kubalek (1966)V . Kubalek (1966) :: impressions byimpressions by
the use of subatmospheric pressurethe use of subatmospheric pressure
.JPD1966:16;213-23..JPD1966:16;213-23.
Described that the denture canDescribed that the denture can
no better be than theno better be than the
impressions by which it is made.impressions by which it is made.
A new concept was developed toA new concept was developed to
eliminate the functional limitationseliminate the functional limitations
of the impressions.of the impressions.

The term “vacustatics” has beenThe term “vacustatics” has been
coined to describe accurately thecoined to describe accurately the
concepts and the techniques.theconcepts and the techniques.the
term describes subatmosphericterm describes subatmospheric
pressure as a significant factor inpressure as a significant factor in
this technique. It then denotes thethis technique. It then denotes the
equilibrium of forces which resultsequilibrium of forces which results
when the controlled vacuum iswhen the controlled vacuum is
appliedapplied

 Richard A. Smith (1973)Richard A. Smith (1973)
Impression border molding with a coldImpression border molding with a cold
cure resin.JPD1973:30;914-17.cure resin.JPD1973:30;914-17.
He described a technique for moldingHe described a technique for molding
the borders of the impression tray withthe borders of the impression tray with
a cold cure resin .a cold cure resin .
Advantage :eliminating the use ofAdvantage :eliminating the use of
stick modeling compound and itsstick modeling compound and its
tempering water bath.tempering water bath.

Impression border molding with aImpression border molding with a
cold cure resin.JPD1973:30;914-17cold cure resin.JPD1973:30;914-17
 principles involved in completeprinciples involved in complete
denturesdentures.JPD1973:29;594-9.JPD1973:29;594-9
 border molding of complete dentureborder molding of complete denture
impressions using a polyether impressionimpressions using a polyether impression
material.JPD1979:41;347-51material.JPD1979:41;347-51 77

It is most applicable with theIt is most applicable with the
elastic impression materialselastic impression materials
because of the possibility of thebecause of the possibility of the
cast fracture in undercut areas ifcast fracture in undercut areas if
rigid tray materials are usedrigid tray materials are used
throught.throught.

 Theorde E. Logan(1973Theorde E. Logan(1973):):
principles involved in completeprinciples involved in complete
denturesdentures.JPD1973:29;594-97..JPD1973:29;594-97.
 He said that: Inadequate mouthHe said that: Inadequate mouth
preparations and improperpreparations and improper
tissue control make adequatetissue control make adequate
impressions and denture basesimpressions and denture bases
impossible.impossible.
 over extention of impressionsover extention of impressions
and subsequently of the dentureand subsequently of the denture
bases may be the result ofbases may be the result of
choice of impression materialschoice of impression materials

 Under extention of the the dentureUnder extention of the the denture
bases may be due to under extendedbases may be due to under extended
 Placement of a posterior palatal sealPlacement of a posterior palatal seal
and perfection of the thickness andand perfection of the thickness and
extension of the denture bordersextension of the denture borders
should be determined by the dentist.should be determined by the dentist.
 Denture-base extension is dependentDenture-base extension is dependent
on the border extension and fullnesson the border extension and fullness
in the impression.in the impression.

 The use of tissue conditioner beforeThe use of tissue conditioner before
the impressions is indicated forthe impressions is indicated for
most patients who are wearing themost patients who are wearing the
dentures.dentures.
 Impressions should be varied toImpressions should be varied to
control tissues where surgery iscontrol tissues where surgery is
contraindicated.contraindicated.
 Dentures require less maintenanceDentures require less maintenance
when impressions are properlywhen impressions are properly
mademade

 The final impressions determineThe final impressions determine
the shape of the basal surface ofthe shape of the basal surface of
the denture and extentions of itsthe denture and extentions of its
borders.borders.
 The impressions made afterThe impressions made after
mouth preparation is basic to allmouth preparation is basic to all
the steps in denture constructionthe steps in denture construction
which follow.which follow.

 Dale E. Smith (1979):Dale E. Smith (1979): one stepone step
border molding of complete dentureborder molding of complete denture
impressions using a polyetherimpressions using a polyether
impression material.JPD1979:41;347-impression material.JPD1979:41;347-
51.51.
 A technique was describedA technique was described
which uses the polyetherwhich uses the polyether
impression material for borderimpression material for border
molding the impression.molding the impression.

This technique has the followingThis technique has the following
advantages:advantages:
There is simultaneous molding ofThere is simultaneous molding of
all borders of either maxillary orall borders of either maxillary or
mandibular impressions.mandibular impressions.
Border molding can beBorder molding can be
accomplished with one insertionaccomplished with one insertion
of the tray.of the tray.

Functional movements performedFunctional movements performed
by the patients are used in borderby the patients are used in border
molding.molding.
The technique is easily masteredThe technique is easily mastered

 Awni Rihani (1981):Awni Rihani (1981): pressurespressures
involved in complete dentureinvolved in complete denture
impressionsimpressions.JPD1981:46;610-14..JPD1981:46;610-14.
 In his study he showed thatIn his study he showed that thethe
pressure in the impression waspressure in the impression was
not equally distributednot equally distributed

 the greatest pressure duringthe greatest pressure during
impression making was recorded byimpression making was recorded by
the manometer located in the centrethe manometer located in the centre
of the palate.of the palate.
 pressures were not able to registerpressures were not able to register
at the borders.at the borders.
 the shape of the palate did notthe shape of the palate did not
effect the distribution of theeffect the distribution of the
pressurespressures


H.Hotkin et al (1987)H.Hotkin et al (1987) ::tonguetongue
positions in relation to mandibularpositions in relation to mandibular
impressionsimpressions . JPD1987:57;458-62.. JPD1987:57;458-62.
Made a study to describe anMade a study to describe an
impression technique that providesimpression technique that provides
a mandibular denture base with thea mandibular denture base with the
contours that encourage anteriorcontours that encourage anterior
positioning of the tongue forpositioning of the tongue for
effective harnessing of theeffective harnessing of the
stabilizing and retentive forcesstabilizing and retentive forces
exerted in the forward positionexerted in the forward position

He concluded that this techniqueHe concluded that this technique
is indicated where advancedis indicated where advanced
residual ridge resorption isresidual ridge resorption is
present. An adjustable easilypresent. An adjustable easily
located impression tray handlelocated impression tray handle
was used as a device to controlwas used as a device to control
tongue position and musculartongue position and muscular
forces for mandibular completeforces for mandibular complete
denture impression –making.denture impression –making.

Mohammed Khaled Ahmed AzzamMohammed Khaled Ahmed Azzam
et alet al (1992):(1992): the sublingual crescentthe sublingual crescent
extensions and its relation to the stabilityextensions and its relation to the stability
and retention of mandibular completeand retention of mandibular complete
dentures.JPD1992:67;205-10.dentures.JPD1992:67;205-10.
He stated that the extension of theHe stated that the extension of the
flange in the sublingual crescentflange in the sublingual crescent
region is an important factor forregion is an important factor for
mandibular denture stability andmandibular denture stability and
retention.retention.

the sublingual crescent extensionsthe sublingual crescent extensions
and its relation to the stability andand its relation to the stability and
retention of mandibular completeretention of mandibular complete
dentures.JPD1992:67;205-10dentures.JPD1992:67;205-10
Functional metallic handles for finalFunctional metallic handles for final
impressions of completeimpressions of complete
denturesdentures.JPD1998:79;607-8.JPD1998:79;607-8

Making the impression with theMaking the impression with the
minimum pressure on the floor ofminimum pressure on the floor of
the mouth while the tongue is atthe mouth while the tongue is at
rest allows greater mobility of therest allows greater mobility of the
underlying tissue without dentureunderlying tissue without denture
dislodgement and withoutdislodgement and without
occlusion of the sublingual glandocclusion of the sublingual gland
ducts.ducts.

The anatomy of the sublingualThe anatomy of the sublingual
crescent region and the clinicalcrescent region and the clinical
procedure for recording theprocedure for recording the
anterior lingual seal region wasanterior lingual seal region was
described. Upon completion ofdescribed. Upon completion of
the impression, resistance to thethe impression, resistance to the
dislodgement is usuallydislodgement is usually
achievedachieved ..

 A.R. Odgen (1994A.R. Odgen (1994):): disposable trays fordisposable trays for
complete denture construction :acomplete denture construction :a
dimensional study of a type frequently useddimensional study of a type frequently used
in UK and its suitability for the edentulousin UK and its suitability for the edentulous
patientspatients.BDJ1994;23:303-9..BDJ1994;23:303-9.
 This study compares the sizes ofThis study compares the sizes of
patients edentulous arches with thepatients edentulous arches with the
shapes of disposable stock trays fromshapes of disposable stock trays from
one manufacturer .in manyone manufacturer .in many
dimensions there is considerabledimensions there is considerable
discrepancy between the twodiscrepancy between the two

It is concluded that , even withIt is concluded that , even with
the tray modification it is almostthe tray modification it is almost
impossible to obtain an accurateimpossible to obtain an accurate
impressions of the shape of theimpressions of the shape of the
all-important sulcus regions. Suchall-important sulcus regions. Such
a conclusion emphesises thea conclusion emphesises the
importance of obtaining furtherimportance of obtaining further
impressions in special traysimpressions in special trays
which are modified appropriately.which are modified appropriately.

 Izharul Haque Ansari (1997):Izharul Haque Ansari (1997):
establishing the posterior palatal sealestablishing the posterior palatal seal
during the final impressionduring the final impression
stage.JPD1997:78;324-25.stage.JPD1997:78;324-25.

A procedure for adding theA procedure for adding the
posterior palatal seal at the finalposterior palatal seal at the final
impression stage with green stickimpression stage with green stick
modeling compound is described.modeling compound is described.
This procedure was suggested toThis procedure was suggested to
be more accurate than thebe more accurate than the
arbitary scraping of the masterarbitary scraping of the master
castcast

The advantages of this methodThe advantages of this method
was :the procedure places thewas :the procedure places the
entire responsibility of locatingentire responsibility of locating
and incorporating the PPS intoand incorporating the PPS into
the hands of the clinician.the hands of the clinician.
the practitioner will then be ablethe practitioner will then be able
to assess the retentive qualitiesto assess the retentive qualities
of the finished dentures.of the finished dentures.

PPS is incorporated into the trialPPS is incorporated into the trial
dentures for added retention ,dentures for added retention ,
thus increasing the diagnosticthus increasing the diagnostic
information and accuracy ofinformation and accuracy of
record taking procedures.record taking procedures.
overcompression of impressionsovercompression of impressions
is avoidedis avoided

The fluid wax technique is theThe fluid wax technique is the
method of choice but it hasmethod of choice but it has
following disadvantages.following disadvantages.
more time is required duringmore time is required during
impression appointmentsimpression appointments
a heating unit is used to conditiona heating unit is used to condition
the wax.the wax.

difficulty may be experienced indifficulty may be experienced in
handling the material.handling the material.
added care during the boxingadded care during the boxing
procedure for cast formation isprocedure for cast formation is
necessary to prevent distortion ofnecessary to prevent distortion of
the carefully added PPS wax.the carefully added PPS wax.

 ALEXANDRE Malachias (1998ALEXANDRE Malachias (1998);:);:
Functional metallic handles for finalFunctional metallic handles for final
impressions of completeimpressions of complete
denturesdentures.JPD1998:79;607-8..JPD1998:79;607-8.
 He stated that one of theHe stated that one of the
fundamental requirement for thefundamental requirement for the
final impressions is the correctfinal impressions is the correct
muscular record that can bemuscular record that can be
achived with the patient or theachived with the patient or the
dentistdentist

His work presented a technicalHis work presented a technical
modification in the completemodification in the complete
denture final impression by usingdenture final impression by using
a removable functional handlea removable functional handle
that can be reusable and can bethat can be reusable and can be
easily attached to acrylic resineasily attached to acrylic resin
individual trays that allowindividual trays that allow
muscular records to be obtainedmuscular records to be obtained
from the patients movementsfrom the patients movements..

 T. Paul Hyde (1999T. Paul Hyde (1999):): survey ofsurvey of
prosthodontic impression proceduresprosthodontic impression procedures
for complete dentures in generalfor complete dentures in general
practice in United Kingdom.practice in United Kingdom.
JPD1999:81;295-9.JPD1999:81;295-9.
 This study identifies the materialsThis study identifies the materials
and methods used by generaland methods used by general
practitioners for recordingpractitioners for recording
impressions for the provision ofimpressions for the provision of
replacement of complete dentures.replacement of complete dentures.

Within the limits of this study ,theWithin the limits of this study ,the
following conclusions were drawnfollowing conclusions were drawn
:Irreversible hydrocolloid:Irreversible hydrocolloid
dominated the market fordominated the market for
impressions materials forimpressions materials for
complete dentures.complete dentures.
the use of special trays is normalthe use of special trays is normal
practice for complete dentures.practice for complete dentures.

Cenk Cura,(2003) Fabrication of aCenk Cura,(2003) Fabrication of a
sectional impression tray and sectionalsectional impression tray and sectional
complete denture for a patient withcomplete denture for a patient with
microstomia and trismus.microstomia and trismus. (J Prosthet
Dent 2003;89:540-3.)
This article describes techniques usedThis article describes techniques used
to fabricate mandibular and maxillaryto fabricate mandibular and maxillary
sectional trays and a folding maxillarysectional trays and a folding maxillary
complete denture for a patient withcomplete denture for a patient with
limited oral opening caused bylimited oral opening caused by
scleroderma.scleroderma.

For the foldable denture, theFor the foldable denture, the
anterior teeth had to be arrangedanterior teeth had to be arranged
on a second base and the hingeon a second base and the hinge
fitted at a location higher than thefitted at a location higher than the
denture base. These 2 factorsdenture base. These 2 factors
increased the thickness of theincreased the thickness of the
denture and limited the volume ofdenture and limited the volume of
the tongue. Nevertheless, a single-the tongue. Nevertheless, a single-
piece denture base provided thepiece denture base provided the
patient with ease in placement andpatient with ease in placement and
removal of the denture.removal of the denture.

Carl J. Drago(2003)Carl J. Drago(2003) A RetrospectiveA Retrospective
Comparison of Two Definitive ImpressionComparison of Two Definitive Impression
Techniques and Their AssociatedTechniques and Their Associated
Postinsertion Adjustments in CompletePostinsertion Adjustments in Complete
Denture ProsthodonticsDenture Prosthodontics.. J Prosthodont
2003;12:192-197.

Compared the number of postinsertionCompared the number of postinsertion
adjustment visits required byadjustment visits required by
edentulous patients whose denturesedentulous patients whose dentures
were made from border-moldedwere made from border-molded
definitive impressions using modelingdefinitive impressions using modeling
plastic impression compoundplastic impression compound
(traditional technique) with patients(traditional technique) with patients
whose dentures were made fromwhose dentures were made from
border-molded definitive impressionsborder-molded definitive impressions
using heavy-body vinyl polysiloxaneusing heavy-body vinyl polysiloxane

They concluded Within theThey concluded Within the
limitations of this clinical study,limitations of this clinical study,
border-molding custom dentureborder-molding custom denture
impression trays with vinylimpression trays with vinyl
polysiloxane impression materialpolysiloxane impression material
provided similar results in terms ofprovided similar results in terms of
postinsertion visits for one year aspostinsertion visits for one year as
compared to dentures made fromcompared to dentures made from
impressions border molded withimpressions border molded with
modeling plastic impressionmodeling plastic impression
compound.compound. www.indiandentalacademy.comwww.indiandentalacademy.com

Vicki C. Petropoulos (2004)Vicki C. Petropoulos (2004)
Current Concepts and TechniquesCurrent Concepts and Techniques
in Complete Denture Finalin Complete Denture Final
Impression ProceduresImpression Procedures J Prosthodont
2003;12:280-287.

In 2001, a survey of U.S. dentalIn 2001, a survey of U.S. dental
schools was conducted toschools was conducted to
determine which concepts,determine which concepts,
techniques and materials aretechniques and materials are
currently prevalent in thecurrently prevalent in the
teaching of final impressionteaching of final impression
procedures for completeprocedures for complete
dentures in the predoctoraldentures in the predoctoral
clinical curriculumclinical curriculum..

Conclusions:Conclusions: Predoctoral clinicalPredoctoral clinical
complete denture educationalcomplete denture educational
programs agree on many aspectsprograms agree on many aspects
of final impression making,of final impression making,
however, there is variability inhowever, there is variability in
their teachings regarding thetheir teachings regarding the
impression philosophy and theimpression philosophy and the
materials used.materials used.

M. M. De Van (2005) basic principlesM. M. De Van (2005) basic principles
in impression making.in impression making. JPD2005:93;503-8JPD2005:93;503-8
The objective of his article was toThe objective of his article was to
bring to your attention the basicbring to your attention the basic
and fundamentals in impressionand fundamentals in impression
making- the impressions of mouthmaking- the impressions of mouth
tissues for the purpose oftissues for the purpose of
constructing mucosa attachedconstructing mucosa attached
complete dentures.complete dentures.www.indiandentalacademy.comwww.indiandentalacademy.com

In conclusion he said that theIn conclusion he said that the
importance of impression phase isimportance of impression phase is
over emphasized. Steps inover emphasized. Steps in
retention have played up while theretention have played up while the
forces that lead to stability haveforces that lead to stability have
not received the emphasis thatnot received the emphasis that
they merit.they merit.

Principles and objectives ofPrinciples and objectives of
impression making.impression making.
The principles involved in impressionThe principles involved in impression
making are:making are:
Preservation of the residual alveolarPreservation of the residual alveolar
tissue.tissue.
Retention.Retention.
Stability.Stability.
Support.Support.
Esthetics.Esthetics. www.indiandentalacademy.comwww.indiandentalacademy.com

Preservation of the residualPreservation of the residual
alveolar tissues:alveolar tissues:
M.M De Van’s dictum”It is moreM.M De Van’s dictum”It is more
important to preserve whatimportant to preserve what
already exists than replace thealready exists than replace the
missing.missing.
It is physiologically accepted thatIt is physiologically accepted that
with loss of stimulation of thewith loss of stimulation of the
natural teeth the alveolar ridgesnatural teeth the alveolar ridges
will atropy and resorb.will atropy and resorb.www.indiandentalacademy.comwww.indiandentalacademy.com

During making impressions itDuring making impressions it
should be kept in mind that theshould be kept in mind that the
impression technique andimpression technique and
materials may have effect on thematerials may have effect on the
health of the hard and softhealth of the hard and soft
tissues.tissues.

Pressure in the impressionPressure in the impression
technique is reflected as pressure intechnique is reflected as pressure in
the denture base and results in softthe denture base and results in soft
tissue damage and bone resorption.tissue damage and bone resorption.
In making impressions this rule isIn making impressions this rule is
followed by not using heavy pressurefollowed by not using heavy pressure
and covering as much as supportingand covering as much as supporting
areas as possible to minimize theareas as possible to minimize the
possibility of soft tissue abuse andpossibility of soft tissue abuse and
bone resorption.bone resorption.www.indiandentalacademy.comwww.indiandentalacademy.com

Retention.Retention.
Retention for a denture is itsRetention for a denture is its
resistance to removal in a directionresistance to removal in a direction
opposite to that of its insertionopposite to that of its insertion
(Boucher).(Boucher).
Retention is that quality of theRetention is that quality of the
prosthesis acting to resist the forcesprosthesis acting to resist the forces
of dislodgement along the path ofof dislodgement along the path of
placement (GPT7).placement (GPT7).www.indiandentalacademy.comwww.indiandentalacademy.com

Denture retention is the resistanceDenture retention is the resistance
of the movement of the dentureof the movement of the denture
from its basal seat, especially in afrom its basal seat, especially in a
vertical direction. (Winkler).vertical direction. (Winkler).

It is the quality inherent inIt is the quality inherent in
dentures to resists the force ofdentures to resists the force of
gravity , adhesiveness of foods,gravity , adhesiveness of foods,
and the forces associated with theand the forces associated with the
opening of the jaws.opening of the jaws.

When the soft tissues over theWhen the soft tissues over the
bones are displaced underbones are displaced under
pressure , the denture bases maypressure , the denture bases may
loose their retention because ofloose their retention because of
change of adaptation of thechange of adaptation of the
denture to the basal seat.denture to the basal seat.

Factors governing the retentionFactors governing the retention
1.Physical factors:1.Physical factors:
adhesion.adhesion.
cohesion.cohesion.
interfacial surface tension.interfacial surface tension.
Capillary attraction.Capillary attraction.
atmospheric pressure.atmospheric pressure.
2.Physiological factors:2.Physiological factors:
physical condition.physical condition.www.indiandentalacademy.comwww.indiandentalacademy.com

degree of tissue tone.degree of tissue tone.
condition of mucosa and submucosa.condition of mucosa and submucosa.
neuromuscular control.neuromuscular control.
ridge characteristics.ridge characteristics.
ridge relationship.ridge relationship.
3.Physcological factors:3.Physcological factors:
intelligence.intelligence.
expectation.expectation.
apprehension or fear of embarrassment.apprehension or fear of embarrassment.
gagging.gagging. www.indiandentalacademy.comwww.indiandentalacademy.com

4.Mechanical factors.4.Mechanical factors.
mechanical locking into themechanical locking into the
undercuts.undercuts.
Contour of denture bases.Contour of denture bases.
magnetsmagnets
Suction chambers.Suction chambers.
5.Surgical.5.Surgical.
Implant dentures.Implant dentures.
ridge extension.ridge extension.www.indiandentalacademy.comwww.indiandentalacademy.com

Physical factors.Physical factors.
Adhesion:Adhesion:
Adhesion is a physical attraction ofAdhesion is a physical attraction of
unlike molecules to each other.unlike molecules to each other.
It acts when saliva wets and sticks toIt acts when saliva wets and sticks to
the basal surface of the dentures andthe basal surface of the dentures and
at the same time , to the mucousat the same time , to the mucous
membrane of the basal seat.membrane of the basal seat.

The effectiveness of adhesionThe effectiveness of adhesion
depends on the closedepends on the close
adaptation of the dentures toadaptation of the dentures to
the supporting tissues andthe supporting tissues and
fluidity of the saliva.fluidity of the saliva.

Saliva that is thick and ropy adheresSaliva that is thick and ropy adheres
well to both the denture base and thewell to both the denture base and the
mucosa; but since much of it ismucosa; but since much of it is
produced by the palatal glands underproduced by the palatal glands under
the maxillary basal seat , it builds upthe maxillary basal seat , it builds up
and literally pushes the denture out ofand literally pushes the denture out of
position.position.
 The forces of adhesion still acts onThe forces of adhesion still acts on
both surfaces , but the hydraulicboth surfaces , but the hydraulic
pressure produced may overpowerpressure produced may overpower
them.them. www.indiandentalacademy.comwww.indiandentalacademy.com

In xerostomia adhesion is notIn xerostomia adhesion is not
effective for retaining dentures.effective for retaining dentures.
Adhesion is best effective in patientsAdhesion is best effective in patients
having mixed type of saliva.having mixed type of saliva.

Patients with small jaws (basalPatients with small jaws (basal
seats) cannot expect retention byseats) cannot expect retention by
adhesion to be as effective asadhesion to be as effective as
patients with large jaws can.patients with large jaws can.
Thus dentures (and hence theThus dentures (and hence the
impressions ) must extend to theimpressions ) must extend to the
limits of the oral tissues if they arelimits of the oral tissues if they are
to have maximum retention byto have maximum retention by
adhesion.adhesion.

Cohesion:Cohesion:
Cohesion is attraction of the likeCohesion is attraction of the like
molecules to each other.molecules to each other.
It is retentive because it occurs in theIt is retentive because it occurs in the
layer of saliva between the denture baselayer of saliva between the denture base
and the mucosa. Since saliva is a liquid,and the mucosa. Since saliva is a liquid,
the layer of saliva should be thin to aid inthe layer of saliva should be thin to aid in
Therefore the adaptation of the dentureTherefore the adaptation of the denture
base to the mucosa should be as close asbase to the mucosa should be as close as
possible.possible.

Cohesive failure means the seperationCohesive failure means the seperation
of molecules within the body againstof molecules within the body against
inter-or intramolecular forces.inter-or intramolecular forces.
The bubbles caused in the saliva filmThe bubbles caused in the saliva film
would certainly cause loss ofwould certainly cause loss of

Interfacial surface tensionInterfacial surface tension
Interfacial surface tension isInterfacial surface tension is
the resistance to thethe resistance to the
separation possessed by theseparation possessed by the
thin film of liquid between twothin film of liquid between two
well adapted surfaces.well adapted surfaces.

Page refers interfacial surfacePage refers interfacial surface
tension as a phenomenon whichtension as a phenomenon which
refer to the forces involved inrefer to the forces involved in
maintaining the attraction of twomaintaining the attraction of two
opposed ground solid plates withopposed ground solid plates with
an intervening fluid film thatan intervening fluid film that
resists displacing forces appliedresists displacing forces applied
at right angles to the fluid filmat right angles to the fluid film
surface.surface.

On assuumption that the denture baseOn assuumption that the denture base
is wetted by the saliva, an attempt tois wetted by the saliva, an attempt to
withdraw denture generates along itswithdraw denture generates along its
periphery a narrow highly negetivelyperiphery a narrow highly negetively
curved saliva surface.curved saliva surface.
There is therefore a lowered pressureThere is therefore a lowered pressure
in the liquid filled space and ain the liquid filled space and a
retentive force is experienced.retentive force is experienced.

It is effective in direct proportionIt is effective in direct proportion
to the size of the basal surface ofto the size of the basal surface of
the dentures.the dentures.
One of its requirements isOne of its requirements is
minimal distortion or displacementminimal distortion or displacement
of the soft tissues by theof the soft tissues by the
impressions and of course theimpressions and of course the
denture.denture.
A perfect fit is essential.A perfect fit is essential.www.indiandentalacademy.comwww.indiandentalacademy.com

Capillary attraction:Capillary attraction:
Capillary action or capillarity is aCapillary action or capillarity is a
force that causes surface of theforce that causes surface of the
fluid to elevate or depressedfluid to elevate or depressed
when it is in contact with a solid.when it is in contact with a solid.

When the adaptation of theWhen the adaptation of the
denture base to the mucosa ondenture base to the mucosa on
which it rests is sufficiently close,which it rests is sufficiently close,
the space filled with a thin film ofthe space filled with a thin film of
saliva acts like a capillary tubesaliva acts like a capillary tube
and helps to retain the denture.and helps to retain the denture.
This force is directly proportionateThis force is directly proportionate
to the area of the basal seatto the area of the basal seat
covered by the denture base.covered by the denture base.

Atmospheric pressure:Atmospheric pressure:
Atmospheric pressure can act toAtmospheric pressure can act to
resist dislodging forces applied toresist dislodging forces applied to
the dentures.the dentures.
It has been called as ”suction”It has been called as ”suction”
because it is a resistance to thebecause it is a resistance to the
removal of the forces from theirremoval of the forces from their
basal seatbasal seat

For atmospheric force to beFor atmospheric force to be
effective the denture should haveeffective the denture should have
a perfect seal around the entirea perfect seal around the entire
border.border.
Sydner et al., in 1945Sydner et al., in 1945
demonstrated the effect ofdemonstrated the effect of
reduced atmospheric pressure onreduced atmospheric pressure on
the retention of maxillarythe retention of maxillary

Measurements made in aMeasurements made in a
pressure chamber at4.7psipressure chamber at4.7psi
simulating a 30,000-footsimulating a 30,000-foot
ascent from the earthascent from the earth
demonstrated a decrease indemonstrated a decrease in
With a 70% decrease in atmWith a 70% decrease in atm
pressure , 50% decrease ofpressure , 50% decrease of
retention was noted.retention was noted.www.indiandentalacademy.comwww.indiandentalacademy.com

For atmospheric pressure to beFor atmospheric pressure to be
effective the seal around theeffective the seal around the
denture is crucial.denture is crucial.
It acts by the way of pressureIt acts by the way of pressure
difference. Beneath the denturedifference. Beneath the denture
there must be a lower pressurethere must be a lower pressure
and the full effect will be felt onlyand the full effect will be felt only
if there is vacumm .if there is vacumm .

Oral and facial musculature:Oral and facial musculature:
The oral and facial musculatureThe oral and facial musculature
can provide retentive forcescan provide retentive forces
provided 1. the teeth areprovided 1. the teeth are
positioned in the neutral zonepositioned in the neutral zone
between the cheeks and thebetween the cheeks and the
tongue. 2. the polished surfacestongue. 2. the polished surfaces
of the tongue are perfectlyof the tongue are perfectly
shaped.shaped. www.indiandentalacademy.comwww.indiandentalacademy.com

The buccal and the lingual flangesThe buccal and the lingual flanges
must be shaped so that it makes itmust be shaped so that it makes it
possible for the musculature to fitpossible for the musculature to fit
automatically against the denture andautomatically against the denture and
reinforce the border seal.reinforce the border seal.
The buccal flanges of the maxillaryThe buccal flanges of the maxillary
denture slope up and out from thedenture slope up and out from the
occlusal surfaces of the teeth and theocclusal surfaces of the teeth and the
buccal flanges of the mandibularbuccal flanges of the mandibular
dentures slope down and out.dentures slope down and out.www.indiandentalacademy.comwww.indiandentalacademy.com

The lingual surfaces of theThe lingual surfaces of the
lingual flanges slope towardslingual flanges slope towards
the center of the mouth so thethe center of the mouth so the
tongue can best fit againsttongue can best fit against
them and perfect the borderthem and perfect the border
seal on the lingual side of theseal on the lingual side of the
denture.denture. www.indiandentalacademy.comwww.indiandentalacademy.com

Physiological factors:Physiological factors:

Ridgecharecteristics:Ridgecharecteristics:
ridge formsridge forms
influence theinfluence the
retention ofretention of
dentures;dentures;
 Classified byClassified by
Charles H MosesCharles H Moses
in mandiblein mandible
 class1A -invertedclass1A -inverted
‘u’ shaped ridge-‘u’ shaped ridge-
very retentivevery retentive
 class1B-flatclass1B-flat
inverted ‘u’shape.inverted ‘u’shape.

Class1 C ‘u’Class1 C ‘u’
shaped: presentsshaped: presents
little retention inlittle retention in
comparision tocomparision to
class1’A’ butclass1’A’ but
resistsresists
displacement indisplacement in
upper direction.upper direction.
Class2 ’v’shapedClass2 ’v’shaped
ridge: is the leastridge: is the least
retentive of all.retentive of all.

Class 3A parallelClass 3A parallel
walled thin ridge:walled thin ridge:
there is no muchthere is no much
retention as theretention as the
area at the crest ofarea at the crest of
ridge is very small.ridge is very small.
Class 3B parallelClass 3B parallel
walled ,broadwalled ,broad
crested ridge: it iscrested ridge: it is
the most retentivethe most retentive
of all.of all. www.indiandentalacademy.comwww.indiandentalacademy.com

Degree of tissue tone:the swellingDegree of tissue tone:the swelling
which is the charecteristic ofwhich is the charecteristic of
inflammation changes the gross forminflammation changes the gross form
of the tissues to be recorded in theof the tissues to be recorded in the
impression.impression.
Inflammation should be reduced byInflammation should be reduced by
keeping the old dentures out of thekeeping the old dentures out of the
mouth until the tissues are healthy. Ifmouth until the tissues are healthy. If
the patient does not agree tissuethe patient does not agree tissue
conditioning materials should beconditioning materials should be
used.used. www.indiandentalacademy.comwww.indiandentalacademy.com

How ever the old dentures should beHow ever the old dentures should be
kept out of the mouth atleast 24hrskept out of the mouth atleast 24hrs
before the impressions are made.before the impressions are made.
If excessive amounts of theIf excessive amounts of the
hyperplastic tissue is present a fingerhyperplastic tissue is present a finger
massage is done on daily basis ormassage is done on daily basis or
surgical removal of the hyperplasticsurgical removal of the hyperplastic
tissue.tissue.

Neuromuscular control: GoodNeuromuscular control: Good
neuromuscular is essential for theneuromuscular is essential for the
effective use of complete dentures.effective use of complete dentures.
When tongue movements are usedWhen tongue movements are used
for border molding the lingual flangesfor border molding the lingual flanges
of the mandibular impression,theof the mandibular impression,the
timing ,the direction and amount oftiming ,the direction and amount of
are critical to the success of molding.are critical to the success of molding.

Mechanical factors:Mechanical factors:
Undercuts, Rotational insertion pathsUndercuts, Rotational insertion paths
and Parallel walls:and Parallel walls:
The resiliency of the mucosa and theThe resiliency of the mucosa and the
submucosa overlying the basal bonesubmucosa overlying the basal bone
allows existance of the modestallows existance of the modest
undercuts that can enhance retention.undercuts that can enhance retention.

Less severe undercuts of lateralLess severe undercuts of lateral
tuberosities , maxillary premolartuberosities , maxillary premolar
area distolingual areas and lingualarea distolingual areas and lingual
mandibular mid bone area aremandibular mid bone area are
extreamly helpful in retention.extreamly helpful in retention.
Some under cuts are onlySome under cuts are only
undercuts in relationship to aundercuts in relationship to a
linear path of insertion.linear path of insertion.

If the undercut is seated first in aIf the undercut is seated first in a
direction that deviates from thedirection that deviates from the
vertical and the remainder of thevertical and the remainder of the
denture base can be brought intodenture base can be brought into
proximity on rotation of theproximity on rotation of the
prosthesis around the undercutprosthesis around the undercut
that is already seated. Thisthat is already seated. This
rotational path provide resistancerotational path provide resistance
to the vertical displacement.to the vertical displacement.

For example : this is found in theFor example : this is found in the
area inferior to the retromolar padarea inferior to the retromolar pad
into which the distolingualinto which the distolingual
extension of the mandibularextension of the mandibular
denture is introduced from thedenture is introduced from the
posterior and the superior beforeposterior and the superior before
rotating the anterior segment ofrotating the anterior segment of
the denture down over thethe denture down over the
alveolar process.alveolar process.

Prominent alveolar ridges withProminent alveolar ridges with
parallel buccal and lingualparallel buccal and lingual
walls provide significantwalls provide significant
Very flat ridges resistsVery flat ridges resists
displacement perpendicular todisplacement perpendicular to
basal seat ,but does not resistbasal seat ,but does not resist
movement parallel to basalmovement parallel to basal
seat.seat. www.indiandentalacademy.comwww.indiandentalacademy.com

Contour of denture basesContour of denture bases::
Craddock described toCraddock described to
maximise the role ofmaximise the role of
denture bases indenture bases in
retention ,properretention ,proper
contour and design ofcontour and design of
the polished surfacesthe polished surfaces
should harmonise theshould harmonise the
function of the lipsfunction of the lips
,cheeks and tongue to,cheeks and tongue to
effect seating of theeffect seating of the
dentures.dentures. www.indiandentalacademy.comwww.indiandentalacademy.com

Magnets: Magnetic retentionMagnets: Magnetic retention
offers many advantages as itoffers many advantages as it
serves to dissipate lateralserves to dissipate lateral
functional forces .functional forces .
Small magnets are embeddedSmall magnets are embedded
beneath the molar and thebeneath the molar and the
premolar teeth and arranged topremolar teeth and arranged to
similar poles to each other. Insimilar poles to each other. In
theory repulsion keeps both thetheory repulsion keeps both the
dentures in place.dentures in place.www.indiandentalacademy.comwww.indiandentalacademy.com

In practice it will be found that ,In practice it will be found that ,
owing to magnetic force beingowing to magnetic force being
inversely proportional to theinversely proportional to the
square of the distance and alsosquare of the distance and also
small size of the magnets which issmall size of the magnets which is
possible to fit, the repulsive effectpossible to fit, the repulsive effect
is undetectable when theis undetectable when the
dentures are seperated by moredentures are seperated by more
then 1-2mm.then 1-2mm.

Suction chambers:Suction chambers:
They resemble relief areas in shape butThey resemble relief areas in shape but
differ by having a clearly defineddiffer by having a clearly defined
outline instead of merging into theoutline instead of merging into the
surrounding surfaces.surrounding surfaces.
When the denture is inserted in theWhen the denture is inserted in the
mouth the patient creates partialmouth the patient creates partial
vaccum in this chamber by sucking,vaccum in this chamber by sucking,
this small area of reduced pressurethis small area of reduced pressure
keeps the denture in place.keeps the denture in place.www.indiandentalacademy.comwww.indiandentalacademy.com

Rubber suction discs: theyRubber suction discs: they
consists of rubber disc whichconsists of rubber disc which
is fixed to a stud on the fittingis fixed to a stud on the fitting
surface of the denture.surface of the denture.
Partial vaccum is createdPartial vaccum is created
within the disc which holds thewithin the disc which holds the
upper denture suspended fromupper denture suspended from
hard palate.hard palate.

Surgical factors:Surgical factors:
The retention of the dentures canThe retention of the dentures can
be increased by the use ofbe increased by the use of
implants.implants.
Ridge corrections:Ridge corrections:
The sharp and spiny residual ridgesThe sharp and spiny residual ridges
,bony tuberosity interferences is,bony tuberosity interferences is
surgically corrected to enhancesurgically corrected to enhance
retention.retention. www.indiandentalacademy.comwww.indiandentalacademy.com

The size of the ridges by surgicalThe size of the ridges by surgical
procedures such as boneprocedures such as bone
grafts,inserts of biomechanicalgrafts,inserts of biomechanical
materials and vestibuloplasties .materials and vestibuloplasties .

Stability:Stability:
Stability is quality of prosthesis to beStability is quality of prosthesis to be
firm, steady, or constant to resistfirm, steady, or constant to resist
displacement by functional horizontaldisplacement by functional horizontal
or rotational stresses(GPT7).or rotational stresses(GPT7).
It refers resistance against horizontalIt refers resistance against horizontal
movement and forces that tend tomovement and forces that tend to
alter the relationship between thealter the relationship between the
denture base and its supportingdenture base and its supporting
foundation in horizontal or rotatoryfoundation in horizontal or rotatory
direction.

The factors that contribute to stability ofThe factors that contribute to stability of
dentures are:dentures are:
1.Ridge anatomy.1.Ridge anatomy.
2.Base adaptation.2.Base adaptation.
3.Residual ridge relationships.3.Residual ridge relationships.
4.Occlusal harmony.4.Occlusal harmony.
5.Neuromuscular control.5.Neuromuscular control.

Ridge anatomy: Large,square, broadRidge anatomy: Large,square, broad
ridges offer greater resistance toridges offer greater resistance to
lateral forces than do small, narrow,lateral forces than do small, narrow,
tapered ridges.tapered ridges.
Small rounded irregularities of theSmall rounded irregularities of the
residual ridges also contributeresidual ridges also contribute
favorable to stability.favorable to stability.

Another factor to be considered inAnother factor to be considered in
stability is the arch form.stability is the arch form.
Square and tapered arches tend toSquare and tapered arches tend to
resists rotation of the prosthesisresists rotation of the prosthesis
better than oviod arches.better than oviod arches.

The shape of the palatal vaultThe shape of the palatal vault
also contributes to stability.also contributes to stability.
A steep palatal vault mayA steep palatal vault may
enhance stability by providingenhance stability by providing
greater surface area of contactgreater surface area of contact
and long inclines approaching aand long inclines approaching a
right angle to the direction ofright angle to the direction of
force.force.

Impression techniques inImpression techniques in

2.Relationship of the denture base to2.Relationship of the denture base to
tissues:tissues:
Friedman describes contacting theFriedman describes contacting the
buccal and lingual flanges with thebuccal and lingual flanges with the
buccal and lingual slopes of the ridgebuccal and lingual slopes of the ridge
is the contributing factor for stability .is the contributing factor for stability .

Adequate extention of the dentureAdequate extention of the denture
base as limited by the movablebase as limited by the movable
tissues not only allows thetissues not only allows the
establishment of the border sealestablishment of the border seal
and coverage of maximumand coverage of maximum
supporting area but also providessupporting area but also provides
maximum contact of the denturemaximum contact of the denture
base with the facial and lingualbase with the facial and lingual
slope ridges.slope ridges.

Optimal denture stability requiresOptimal denture stability requires
that those tissues that providethat those tissues that provide
resistance to the horizontal forcesresistance to the horizontal forces
be properly recorded and relatedbe properly recorded and related
to denture base.to denture base.

Boucher notes that stability isBoucher notes that stability is
obtained by incorporating theobtained by incorporating the
surfaces of the maxillary andsurfaces of the maxillary and
mandibular ridges which are atmandibular ridges which are at
right angle to the occlusal plane.right angle to the occlusal plane.
He further states that stabilityHe further states that stability
requires “maximum use of allrequires “maximum use of all
bony foundations where thebony foundations where the
tissues are firmly attached totissues are firmly attached to
bone”bone” www.indiandentalacademy.comwww.indiandentalacademy.com

Residual ridge relationships:Residual ridge relationships:
A problem of stability is seen inA problem of stability is seen in
prognathic and retrognathicprognathic and retrognathic
patients.patients.
Normal dental relationships of theNormal dental relationships of the
artificial teeth set on ridges thatartificial teeth set on ridges that
are in severe posterior crossbiteare in severe posterior crossbite
can adversely affect stability.can adversely affect stability.

In complete dentures the normalIn complete dentures the normal
tooth –tooth position may betooth –tooth position may be
altered to enhance retention andaltered to enhance retention and
stability.stability.
Weinberg recognizes the need toWeinberg recognizes the need to
set the artificial teeth in cross biteset the artificial teeth in cross bite
when the ridges are in severewhen the ridges are in severe
crossbite.crossbite.

In class III patients they frequentlyIn class III patients they frequently
display a lower arch anterior to indisplay a lower arch anterior to in
centric relation.centric relation.
This causes the maxillary dentureThis causes the maxillary denture
to tip anteriosuperiorly ,to tip anteriosuperiorly ,
traumatizing the maxillarytraumatizing the maxillary
anterior ridge and loosening theanterior ridge and loosening the
maxillary denture.maxillary denture.

Occlusal harmony:Occlusal harmony: to minimizeto minimize
the dislodging forces thethe dislodging forces the
occlusion should be balancedocclusion should be balanced
throughout the functionalthroughout the functional
range of movement of therange of movement of the
patient.patient.

Tooth position and occlusal plane:Tooth position and occlusal plane:
A mandibular occlusal plane that is tooA mandibular occlusal plane that is too
high can reduce the denture stabilityhigh can reduce the denture stability
because:because:
1.Lateral tilting forces directed against1.Lateral tilting forces directed against
the teeth are magnified as the plane isthe teeth are magnified as the plane is
raised.raised.
2.An elevated plane prevents the2.An elevated plane prevents the
tongue from reaching the over thetongue from reaching the over the
food table in the buccal vestibule.food table in the buccal vestibule.

This compromises stability andThis compromises stability and
makes control of the food bolusmakes control of the food bolus
and denture more difficult.and denture more difficult.

Occlusal plane: the best stability isOcclusal plane: the best stability is
obtained when the occlusal plane isobtained when the occlusal plane is
parallel to and anatomically orientedparallel to and anatomically oriented
to the ridges.to the ridges.
If the occlusal plane is tipped there isIf the occlusal plane is tipped there is
shunting effect and a loss of stability.shunting effect and a loss of stability.

Relationship of the external surfaceRelationship of the external surface
and periphery to surroundingand periphery to surrounding
orofacial musculature:orofacial musculature:
Actions of the muscles on theActions of the muscles on the
denture base generally result indenture base generally result in
the lateral and the verticalthe lateral and the vertical
dislodging forces.dislodging forces.

The relationship of external surfaceThe relationship of external surface
with the denture basewith the denture base

The denture borders should beThe denture borders should be
extended to contact the movableextended to contact the movable
tissues. This enhances stability.tissues. This enhances stability.
The actions of the canninus, incisivus,The actions of the canninus, incisivus,
triangularis, mylohyoid, mentalis andtriangularis, mylohyoid, mentalis and
genioglossus muscles can lead togenioglossus muscles can lead to
dislodging forces if the denture basesdislodging forces if the denture bases
does not provide freedom for thesedoes not provide freedom for these
muscles to action.muscles to action.

The basic geometric design of theThe basic geometric design of the
denture bases should bedenture bases should be
triangular.triangular.
In frontal cross section , both theIn frontal cross section , both the
dentures should appear as twodentures should appear as two
triangles whose apex correspondtriangles whose apex correspond
to the occlusal surface.to the occlusal surface.

The buccal and labial flanges of theThe buccal and labial flanges of the
maxillary and the mandibular denturesmaxillary and the mandibular dentures
should be concave to permit positiveshould be concave to permit positive
seating of the lips and cheeks. theseating of the lips and cheeks. the
proper contour of the flanges permitsproper contour of the flanges permits
the horizontally directed forces thatthe horizontally directed forces that
occurs during the contraction ofoccurs during the contraction of
buccinator and orbicularis orisbuccinator and orbicularis oris
muscles to be transmitted as verticalmuscles to be transmitted as vertical
forces tending to seat the prosthesis.forces tending to seat the prosthesis.

Support:Support:
Support is the resistance of aSupport is the resistance of a
denture to the vertical components ofdenture to the vertical components of
mastication and to occlusal forces ormastication and to occlusal forces or
other forces applied in directionother forces applied in direction
towards the basal seat. (boucher)towards the basal seat. (boucher)
Support is the resistance to verticalSupport is the resistance to vertical
movement of the denture basemovement of the denture base
towards the ridge. (Jacobson andtowards the ridge. (Jacobson and
Krol)Krol) www.indiandentalacademy.comwww.indiandentalacademy.com

Support can be considered from twoSupport can be considered from two
points of view:points of view:
1.Maxillary and mandibular dentures1.Maxillary and mandibular dentures
should conform to the underlyingshould conform to the underlying
tissues so that the occlusal surfacestissues so that the occlusal surfaces
can correctly oppose one another atcan correctly oppose one another at
the time of insertion.the time of insertion.
2.The denture bases should maintain2.The denture bases should maintain
this relationship for a period of time.this relationship for a period of time.

Initial denture support is achievedInitial denture support is achieved
by using impression proceduresby using impression procedures
that provide optimal extensionthat provide optimal extension
and functional loading ofand functional loading of
supporting tissues, which vary insupporting tissues, which vary in
their resiliency.their resiliency.

Long-term support is obtained byLong-term support is obtained by
directing the forces of occlusaldirecting the forces of occlusal
loading toward the tissues mostloading toward the tissues most
resistant to remodelling andresistant to remodelling and
resorptive changes.resorptive changes.

Effective support is realized whenEffective support is realized when
The denture is extended to cover aThe denture is extended to cover a
maximal surface area withoutmaximal surface area without
impinging on movable tissues .impinging on movable tissues .
The tissues most capable of resistingThe tissues most capable of resisting
resorption are loaded during function.resorption are loaded during function.
The tissues most capable of resistingThe tissues most capable of resisting
vertical displacement are allowed tovertical displacement are allowed to
make firm contact with the denturemake firm contact with the denture
base during functionbase during functionwww.indiandentalacademy.comwww.indiandentalacademy.com

Compensation is made for theCompensation is made for the
varying tissue resiliency tovarying tissue resiliency to
provide for uniform denture baseprovide for uniform denture base
movement under function andmovement under function and
maintain a harmonious occlusalmaintain a harmonious occlusal
relationship.relationship.

Nature of supporting tissues:Nature of supporting tissues:
Ideally ,the soft tissues should beIdeally ,the soft tissues should be
-firmly bound to underlying cortical-firmly bound to underlying cortical
bonebone
-contain resilient layer of-contain resilient layer of
submucosa , and be covered bysubmucosa , and be covered by
keratinised mucosa.keratinised mucosa.

The underlying bone should be :The underlying bone should be :
-resistant to pressure induced-resistant to pressure induced
remodeling.remodeling.
-cortical bone is more resistant to-cortical bone is more resistant to
resorption than cancellous bone.resorption than cancellous bone.

The areas of support :The areas of support :
Primary areas of support: Areas of thePrimary areas of support: Areas of the
edentulous ridge that are at rightedentulous ridge that are at right
angles to the occlusal forces andangles to the occlusal forces and
donot resorb easily.donot resorb easily.
Maxillary- residual ridge, horizontalMaxillary- residual ridge, horizontal
portion of hard palate.portion of hard palate.
Mandible-buccal shelf area .Mandible-buccal shelf area .

Secendory:Secendory:
Maxilla:rugea areasMaxilla:rugea areas
Mandible: slopes of the residualMandible: slopes of the residual
ridge.ridge.

Importance of covering the buccalImportance of covering the buccal
shelf:shelf:
It is the area of support because:It is the area of support because:
It has a cortical bone.It has a cortical bone.
It is at right angle to the occlusal plane.It is at right angle to the occlusal plane.
When the ridge is flat the buccinator isWhen the ridge is flat the buccinator is
almost attached to the centre of thealmost attached to the centre of the
ridge. The denture can cover this arearidge. The denture can cover this area
as this muscle is flaccid and inactiveas this muscle is flaccid and inactive
as its fibers function in horizontalas its fibers function in horizontal
direction.direction. www.indiandentalacademy.comwww.indiandentalacademy.com

In the maxilla horizontal portion ofIn the maxilla horizontal portion of
the hard palate lateral to midthe hard palate lateral to mid
palatine raphe should providepalatine raphe should provide
primary support to completeprimary support to complete
dentures because the submucosadentures because the submucosa
contains fatty tissue anterolaterallycontains fatty tissue anterolaterally
and glandular tissueand glandular tissue
posteriolaterally. This resilientposteriolaterally. This resilient
layer acts as a cushion to thelayer acts as a cushion to the
functional stresses.functional stresses.

It is enhanced by selectiveIt is enhanced by selective
placement of the pressures thatplacement of the pressures that
are in harmony with theare in harmony with the
resiliency of the tissues thatresiliency of the tissues that
make up the basal seat.make up the basal seat.

Esthetics:Esthetics:
The role of esthetics in impressionThe role of esthetics in impression
making refers to the development ofmaking refers to the development of
the labial and buccal borders so thatthe labial and buccal borders so that
they are not only retentive but alsothey are not only retentive but also
support the lips and the cheeks.support the lips and the cheeks.
These structures should not be overThese structures should not be over
supported with borders that are toosupported with borders that are too
thick.thick.

Hence it is ideal to completeHence it is ideal to complete
the impressions with thethe impressions with the
peripheral width that will beperipheral width that will be
utilized in the polishedutilized in the polished
dentures.dentures.

Theories of impression making:Theories of impression making:
Mucostatic theory/minimalMucostatic theory/minimal
pressure impressions.pressure impressions.
MucocompressiveMucocompressive
theory/definitive pressuretheory/definitive pressure
Selective pressure.Selective pressure.

Mucocompressive theory:Mucocompressive theory:
Because denture retention is tested mostBecause denture retention is tested most
severly during mastication, manyseverly during mastication, many
dentists formerly considered it isdentists formerly considered it is
essential for the tissue to remain inessential for the tissue to remain in
contact with the denture during chewing.contact with the denture during chewing.
It appeared logical to them to makeIt appeared logical to them to make
impressions that would press the tissuesimpressions that would press the tissues
in the same manner as the chewingin the same manner as the chewing
forces.forces.

However the dentures did notHowever the dentures did not
fit well at rest , becausefit well at rest , because
tissues distorted tend totissues distorted tend to
rebound.rebound.
There was a question weatherThere was a question weather
tissues so abused will longtissues so abused will long
maintain the shape that theymaintain the shape that they
assumed during the day ofassumed during the day of
impression.impression.www.indiandentalacademy.comwww.indiandentalacademy.com

Advocates of this techniqueAdvocates of this technique
closed-mouth procedures (Trydeclosed-mouth procedures (Tryde
et al.,) this technique presumeset al.,) this technique presumes
that the occlusal loading duringthat the occlusal loading during
the impression will be same asthe impression will be same as
the occlusal loading duringthe occlusal loading during
function.function.

Critics of this procedure point outCritics of this procedure point out
that the dentures are in actualthat the dentures are in actual
occlusal contact only for a shortocclusal contact only for a short
period of time and the constantperiod of time and the constant
pressure will over-stress thepressure will over-stress the
tissuestissues

This theory of impression makingThis theory of impression making
was not always able to obtain thewas not always able to obtain the
desired pressure but tended todesired pressure but tended to
create excessive pressure.create excessive pressure.
This often resulted in good initialThis often resulted in good initial
retention but eventual boneretention but eventual bone
resorption and loose dentures.resorption and loose dentures.

Mucostatic impression theory:Mucostatic impression theory:
Addison in 1944 described theAddison in 1944 described the
mucostatic impressions andmucostatic impressions and
attributed them to Page.attributed them to Page.
The main point of the mucostaticThe main point of the mucostatic
principle concerned Pascal’s lawprinciple concerned Pascal’s law
which states that “the pressure onwhich states that “the pressure on
the confined liquid will bethe confined liquid will be
transmitted throught the liquid intransmitted throught the liquid in
all directions”.all directions”.www.indiandentalacademy.comwww.indiandentalacademy.com

According to this concept. mucosaAccording to this concept. mucosa
being more than 80% of water willbeing more than 80% of water will
react like liquid in a closed vesselreact like liquid in a closed vessel
and thus cannot be compressed.and thus cannot be compressed.
This is not true, insofar the fluidsThis is not true, insofar the fluids
escape from the border of theescape from the border of the
denture.denture.
The mucosa is not a closed vessel.The mucosa is not a closed vessel.

According to this principle theAccording to this principle the
impression material should record,impression material should record,
without distortion, every detail ofwithout distortion, every detail of
the mucosa so that the completedthe mucosa so that the completed
denture will fit in the elevations anddenture will fit in the elevations and
depressions . For this reasondepressions . For this reason
separating medium was not usedseparating medium was not used
at any point of the procedure.at any point of the procedure.

But the draw back was theBut the draw back was the
impression materials and the castsimpression materials and the casts
exhibited sufficient dimensionalexhibited sufficient dimensional
change to render worthless thechange to render worthless the
care taken to record all the minutecare taken to record all the minute
details.details.
Mucostatics further demand the useMucostatics further demand the use
of metal base than theof metal base than the
dimensionally unstable acrylics.dimensionally unstable acrylics.

But Stephen in 1946 told that theBut Stephen in 1946 told that the
mucosal topography is not static overmucosal topography is not static over
24hr period. There is difference24hr period. There is difference
between the mucosal contour justbetween the mucosal contour just
after rising in the morning , and thatafter rising in the morning , and that
which exists after 12hrs in uprightwhich exists after 12hrs in upright
position.position.
So it would appear that the achievedSo it would appear that the achieved
impression would be altered by theimpression would be altered by the
time the denture is finished.time the denture is finished.www.indiandentalacademy.comwww.indiandentalacademy.com

This principle considered interfacialThis principle considered interfacial
surface tension as the only importantsurface tension as the only important
retentive mechanism in the completeretentive mechanism in the complete
dentures.dentures.
 Therefore they did not useTherefore they did not use
conventional flanges because theyconventional flanges because they
could not resists the verticalcould not resists the vertical
displacement ,with was only thedisplacement ,with was only the
movement interrupting the surfacemovement interrupting the surface
tension.tension. www.indiandentalacademy.comwww.indiandentalacademy.com

Dykins in 1947 recommended shortDykins in 1947 recommended short
lingual flange that resists laterallingual flange that resists lateral
movements.movements.
The mucostatic principle ignores theThe mucostatic principle ignores the
value of dissipating the masticatoryvalue of dissipating the masticatory
forces over largest possible basalforces over largest possible basal
seat area.seat area.
The mucostatic denture minimizedThe mucostatic denture minimized
the retentive role of muscles, asthe retentive role of muscles, as
described by Fish in1948.described by Fish in1948.

Selective pressure theory:Selective pressure theory:
This theory combines pressure overThis theory combines pressure over
certain areas and little pressure overcertain areas and little pressure over
others.others.
The principle behind this theory is basedThe principle behind this theory is based
on the belief that the mucosa over theon the belief that the mucosa over the
ridge is best able to withstand pressure,ridge is best able to withstand pressure,
whereas that covering the midline is thinwhereas that covering the midline is thin
and contains very little submucosaland contains very little submucosal
tissue (Boucher, 1951).tissue (Boucher, 1951).

How ever this technique demandsHow ever this technique demands
firm, healthy mucosal coveringfirm, healthy mucosal covering
over the ridge.over the ridge.
If flabby ridges exists, it isIf flabby ridges exists, it is
preferable to use a minimalpreferable to use a minimal
pressure impression.pressure impression.

Impression techniques.Impression techniques.
Classification:Classification:
1.1. Amount of pressure usedAmount of pressure used
-minimal pressure technique.-minimal pressure technique.
-mucocompressive technique.-mucocompressive technique.
-selective pressure technique.-selective pressure technique.
2.Open or closed mouth technique.2.Open or closed mouth technique.
3.Hand manipulations or functional3.Hand manipulations or functional
movements.movements.
4.Type of tray.4.Type of tray.

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