Impression anoop/prosthodontic courses

THEORIES OF IMPRESSION MAKING
AND IMPRESSION PROCEDURE FOR
COMPLETE DENTURE
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Contents
Introduction
History
Review of literature
Basic requirements of impression making
Principles of impression making
Classification of impression techniques
Various impression techniques
Steps in impression making
Primary impression making
Border molding and secondary impression making
Impression techniques in compromised situations
Summary and conclusion
References www.indiandentalacademy.com

Introduction
Complete denture impression procedures are perhaps one
phase on which much has been spoken about. The
literature on the subject shows a persistent disagreement
ever since 1850.
Much of this confusion results from the fact that many
impression procedures have been developed on empirical
basis.
Many have used the available knowledge of functional and
histological anatomy for the development of their
procedures, but the variation in these techniques indicate a
wide difference in interpretation of the foundation of
dentures.
Whatever the method used it is generally agreed that good
impressions are basic for the construction of a good
denture. www.indiandentalacademy.com

“Ideal impression must be in the mind of the dentist before it
is in his hand. He must literally make the impression rather
than take it”
- M.M. Devan

History
1711 Matthian G. Purman introduced the use
of wax.
1728 Pierre Fauchard
1844 Plaster of paris was first used as an
impression material.
1845-1899 concepts of atmospheric pressure,
maximum extension of denture bearing area,
equal distribution of pressure and close
adaptation of the denture bearing tissues were
stressed.
1886 Richardson
1896 Green brothers introduced
mucocompressive theory.
1900-1920 Concepts like Rebase impressions,
border molding and techniques for flabby
tissues were introduced.www.indiandentalacademy.com

1920-1946
1944 Addison
1946 Page introduced mucostatic concept
1948-1964 more emphasis on biologic factor
of impression making was given.
1950 selective pressure theory by boucher.
1965-1980 new techniques to manage
compromised situations were introduced.
New techniques are periodically been
formulated to overcome the drawbacks faced.
“We have come a long way from the use of
wooden blocks to the use of modern
elastomeric materials to make impressions and
from the use of pressure technique to selective
pressure technique”.

Review of Literature

Fischer in 1951 laid down six fundamental rules for making
an impression
Radiographs ,visual and digital examination
Surgical
Required extension outline
Required retention outline
Required adaptation
Location and position of variable tissue
displaceability

A critical analysis of Mid-century impression techniques for
full dentures
Boucher in 1951 – he classified impression
techniques
1. Based on the use of actual anatomy of the individual
patient or on arbitrary landmarks
Anatomic or Arbitrary
2. Based upon the mouth position while the impression is
made.
Open mouth or closed mouth
3. Based upon the relative amount of pressure exerted
on the tissues by the impression material at the time
of set.
Pressure, non pressure or selective pressure

Impression by the use of subatmospheric pressure – Milo V.
Kubalek, Bert C. Buffington (1966)
The objective of this technique is to reduce the stress on
any given tissue by increasing the load bearing area.
To realize the ideal the form of tissues must be recorded
both vertically and laterally so that all surfaces can bear an
equal load and vacustatic technique is an attempt to
achieve this.
When a controlled partial vacuum is established, an
impression tray specially built for the patient is maintained
in the mouth without direct mechanical support of any
kind.
The difference between subatmospheric pressure within
the tray and atmospheric pressure outside is all that
retained the impression in a static position.
It denotes the equilibrium of forces which results when a
controlled vacuum is established.www.indiandentalacademy.com

Fabrication of a custom made impression tray for making
preliminary impressions of edentulous mandible- A.M.
Sofou, Mordohai, Pissiotis (1998)
The purpose of this article was to demonstrate a technique
in which custom tray is fabricated to achieve suitable
coverage of the edentulous areas in patients with extreme
ridge resorption and thus to obtain proper preliminary
impressions.

The management of abused oral tissues in complete denture
construction – Robert B. Lytle (1957)
The purpose of this article is to emphasize the
need for permitting abused tissues to recover and
to suggest measures for accomplishing their
recovery.
In order to eliminate pressure areas that might
destroy the supporting structures abused soft
tissues must be allowed to recover and return to a
more normal form before impressions are made
for new dentures.
We must be concerned with the health of soft
tissues if the ridges are to be preserved and
dentures to function properly.

Diurnal variation in palatal tissue thickness – Stephens, Cox,
Sharry (1966)
In this study the variation in palatal thickness at
different time of the day is measured.
A small micrometer was attached to an acrylic
resin hood which straddled the upper arch and
fitted the occlusal surface of the molar and
premolar teeth was used to measure the diurnal
changes in palatal tissue.
The results indicated that the palatal tissues were
thickest when the subjects were lying in bed after
a full night sleep and it starts to shrink in the
morning and continues in the afternoon. Slight
increase in tissue thickness is seen again in the
evening. www.indiandentalacademy.com

Impressions for complete denture using new silicone
impression materials – Iwao Hayakawa, Ikki Watanabe (2003)
This article describes a convenient technique for making
impressions of complete dentures using two newly
developed silicone materials.
One of these materials, heavy-bodied silicone materials, is
used for simultaneous molding of all borders. This material
is designed to have a low elasticity after setting.
The other newly developed material, a light-bodied
silicone material, possesses better flow than the usual
light-bodied silicones.
In addition, since viscosity is controlled an adequate flow
is maintained during seating in the mouth, mucosal detail
was found to be superior.

Basic Requirements for Impression Making
Knowledge of Basic anatomy
Knowledge of basic reliable technique
Knowledge and understanding of
impression materials
Skill
Patient management

Definition: A complete denture impression is a negative
registration of the entire denture bearing, stabilizing and
border seal areas present in the edentulous mouth
PRINCIPLES OF IMPRESSION MAKING
Preservation of Alveolar Ridges
Support
Retention
Stability
Esthetics

M.M.DEVAN DICTUM
PRESERVATION OF WHAT REMAINS RATHER THAN
METICULOUS REPLACEMENT OF WHAT IS MISSING
PRESERVATION OF ALVEOLAR RIDGES
Resistance to vertical forces of mastication and to
occlusal or other forces applied in direction
toward the basal seat
SUPPORT

FACTORS FOR RETENTION
ADHESION
COHESION
INTERFACIAL SURFACE TENSION
ATMOSPHERIC PRESSURE
ORAL AND FACIAL MASCULATURE
MECHANICAL INTERLOCKING INTO UNDERCUTS
RETENTION

Ability to remain in place when it is subjected to horizontal
forces.
Factors :-
1. Retention
2. Non interfering occlusion.
3. Proper form & contour of the polished surfaces
4. Proper orientation of occlusal plane
5. Good control and coordination of patients
musculature.
6. Proper tooth arrangement.
ESTHETICS
Refers to development of labial and buccal borders so that
they are not only retentive but also support the lips and
cheeks properly
STABILITY

Impression techniques may be classified depending on:
a) Amount of pressure used
1. Pressure technique
2. Minimal pressure technique
3. Selective pressure technique
b) Based on the position of the mouth while making
impression
1. Open mouth
2. Close mouth
c) Based on the method of manipulation for border
molding.
1. Hand manipulation
2. Functional movements

Pressure theory or mucocompressive theory:
This theory was proposed on the
assumption that tissues recorded under
functional pressure provided better support
and retention for the denture.
Green in 1896 gave this concept
Technique by Green as described by
Liberthal

Greene all compound technique described by
Liberthal
Primary impression made with impression
compound
Special tray made
Impression made with compound
Bite rim made with compound
Relief of mid palatine raphae
Peripheral muscle trimming
Borders are molded by asking the patient to
perform functional movements.

Demerits of the theory
1. Excess pressure could lead to increase alveolar
bone resorption.
2. Excess pressure was often applied to the
peripheral tissues and the palate.
3. Dentures which fit well during mastication tend
to rebound when the tissue resume their normal
resting state.
4. Pressure on sharp bony ridges results in pain.

Applied aspects:
The technique tells that border tissues are recorded
in their functional positions and denture cannot be
dislodged during functional movements of jaws.
The pressure applied is more and directed towards
the palate and peripheral tissues. So the retention
will be for short time and will be lost as soon as
the bone undergoes resorption.
Usually this technique is used for preliminary
impression making as it gives a positive peripheral
seal and tissues are recorded in function. Amount
of pressure applied is for short duration and the
areas can be relieved during the final impression.

Minimal pressure or mucostatic theory – The
main advantage of this technique is its high regard
for tissue health & preservation.
1886 Richardson made impressions of tissues at
rest.
1944 Addison emphasized on interfacial surface
tension.
1946 Page gave the concept of mucostatic based
on Pascal’s law.
1956 Tilton G.E.stated that minimum pressure is
just the amount that will hold movable tissue for
enough away so that the required coverage may be
secured and in substance it is little more than the
weight of a free-flowing material.

Technique
A compound impression is made.
A baseplate wax space is adapted.
A special tray is made.
Spacer is removed and an impression is made with
a free flowing material with little pressure.
Escape holes are made for relief.

Demerits
Application of Pascals law is partially correct
Retention obtained only by interfacial surface
tension is not correct
The lack of border molding reduces effective
peripheral seal.
The short flanges may reduce support for the face.
The shorter flanges prevent the wider distribution
of masticatory stresses.
Least importance to polished surface and muscle
relation

Applied aspect:
The technique holds good in the sense it helps in
preservation of tissue health.
In practice which short flanges the oral
musculature is non supported and stresses are not
widely distributed.
Food can slip beneath the denture and tongue can
readily access the denture borders.
This technique is useful in impressions of flabby
and sharp or thin ridges.

Selective pressure theory
Advocated by Boucher in 1950 it combines the
principles of both pressure and minimal pressure
technique. In this technique idea of tissue
preservation is combined with mechanical factor
of achieving retention, through minimum pressure
which is within physiologic limits of tissue
tolerance.
This theory is based on a thorough understanding
of the anatomy and physiology of basal seat and
surrounding areas.
Boucher also advocated maximum extension
within the comfort and functional limits of the
surrounding muscle and tissues.www.indiandentalacademy.com

Demerits
It is impossible to record areas with varying
pressure.
Some areas still recorded under functional
load, the dentures still faces the potential
danger of rebounding and loosing retention.

Applied aspect:
Inspite of some of its apparent drawbacks all the
impression techniques based on the selective
pressure technique are still popular.
Final impressions using this technique are made
where relief areas are provided and pressure is
distributed on the stress bearing areas.
“Yesterday’s controversies will become today’s
reality & today’s reality will become tomorrow’s
controversy”

Open mouth technique
Made with tray held by dentist and mouth
open
Muscle movements may be emphasized
and can be seen by the operator

Closed mouth technique
The rational behind this technique is that the
supporting tissues are recorded in a
functional relationship.
Requires occlusal rims to be made
Border molding done and final impressions
made
Jaw relations either tentative or final made

Disadvantages-
Fatiguing to patient and dentist
Tendency for over extension
Release of pressure of occlusion may permit
a rebound of denture
Pressure applied cannot be controlled

Hand manipulation
Dentist uses hand manipulation for
movements of lips and cheeks
Functional movements
Patient makes functional movements such as
sucking, swallowing, licking or grinning

STEPS IN MAKING AN IMPRESSION
Preliminary examination of the patient
Seating the patient
Selection of the tray
Selection of the material
Making impression-primary
border molding
secondary

Preliminary examination of the patient
A complete case history and thorough
clinical examination is done.
Factors that can complicate impression
making are identified.
Patient education.

Seating of the patient
Position of the operator for
maxillary impression
Position of the operator for
mandibular impression

Selection of tray:
“The journey of thousand miles begins with one
step”
The beginning of good impression starts with the
selection of the correct stock tray.
Tray is a device that is used to carry, confine and
control impression material while making an
impression.
The space available in the mouth for upper
impression is studied carefully by observation of
the width and height of the vestibular spaces with
mouth partly open.
And in the lower the general form and size of
basal seat is studied.

Primary impression making
With alginate (Maxillary)

(Mandibular impression with alginate)

Preliminary impressions using impression compound
(Maxillary)

(Mandibular)

Making of special tray

Border molding

Secondary impression

Mandibular border molding

Mandibular secondary impression

Impression techniques in compromised situations
Techniques are modified in compromised
situations to achieve as much retention and
stability as possible within limits.
1. Hyper active gag reflex
2. Restricted mouth opening
3. Severely resorbed mandibular ridge
4. Hypermobile / hyperplastic ridges

Hyperactive gag reflex
Patients problems should be identified before impression is
made.
a) Prosthodontic management
- Avoid thick or over extended trays.
- Avoid excess loading of material
- Use a fast setting material
- Singer’s marble technique can be followed
b) Distraction maneuvers
- Engage the patient in conversation of some special
interest.
- Kovats and Krol suggested method can be followed
c) Pharmacologic measures
- Local anaesthetics
- Antihistamines, Sedatives, CNS depressants
d) Psychological intervention
- Hypnosis helpful in certain caseswww.indiandentalacademy.com

Restricted mouth opening
Patient’s may exhibit limited opening of the
mouth following radical surgery or a sequel
facial burns, or due to other pathological
conditions.
Impressions with the use of sectional trays
are made.

Severely resorbed mandibular ridge
Lack of ideal amount of supporting structures decreases
support and encroachment of the surrounding mobile
tissues onto the denture border reduces both stability and
retention. The main is to gain maximum area of coverage.
Flange technique by Lott & Levin involves making
impressions of the soft structures of the mouth adjacent to
the buccal, lingual and palatal surfaces and incorporating
the resulting extension or flange into the denture.
Tryde used the dynamic impression method.
Krammeck used modelling compound to record the
extensions.

Hypermobile or hyperplastic ridges
These ridges should be recorded without
distortion.
Zafrulla Khan technique.
Hobkirk technique and
Filler technique

SUMMARY & CONCLUSION
The main objective of impression making is to
construct dentures, having maximum retention and
stability, without causing any damage to the
supporting structures.
Dentists should be able to modify his technique to
cope with the conditions of the basal tissues as
presented by each patient.
Thus, it is the responsibility of the dentist, to
select the best possible procedures, based on
sound knowledge, for achieving the best possible
results for the patient.

REFERENCES
Bernard Levin – Impression for complete dentures.
Boucher’s – Prosthodontic treatment for edentulous patients –
11th
Edition.
Charles M. Heartwell – Syllabus of complete dentures – 4th
Edition.
Sheldon Winkler – Essentials of complete denture
prosthodontics – 2nd
Edition.
John Joy Manappallil – Complete denture prosthodontics – 1st
Edition.
Boucher C.O. – A critical analysis of mid-century impression
technique for complete denture. JPD 1951; Vol-1.
Lee Singer – The marble technique:A method for treating the
hopeless gagger for complete dentures.JPD 1973;VOL-29
Behruz J Abadi,Gatlazzi –Impression tray for making complete
denture impressions.Quintessance Int 1986;vol-10

M.M. Devan – Basic principles of impression making. JPD
1952, Vol-2.
Chastain and Porter – “Mucostatics” – Panacea or Propoganda –
JPD, 1953; Vol-3.
George A. Buckley – Diagnostic factors in the choice of
impression material and methods. JPD, 1955 Vol-5.
Henry A. Collett – Complete denture impressions. JPD 1965;
Vol-15.
Iwao Hayakawa, Ikki Watanabe - Impressions for complete
denture using new silicone impression materials Quintessence
Int. 2003;34.
A.M Sofou,Mordohai,Pissoti – Fabrication of a custom made
impression tray for making preliminary impression of
edentulous mandible. Quintessence Int.1998;VOL-29
Tryde,Kaisa olsson,A.A Jensen – Dynamic impression
methods.JPD 1965;VOL-16

THANK YOU
“Good Impressions Last
Forever”

Impression anoop/prosthodontic courses

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