Impression procedures for compromised ridges/cosmetic dentistry courses

Impression procedures
for compromised ridges
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indianentalacademy.com

Definition (GPT-7)
• A negative likeliness or copy in reverse of
the surface of an object ;
• An imprint of the teeth and adjacent
structures for use in dentistry.

Impression procedures
for compromised ridges

• 1711 : Matthias Gottfried Durmann recorded the
use of wax.
• 1736, Philip Ptaff of Germany (the impressions
were made in wax sections of half of the mouth at
a time).
• 1845 : Westcott, Dwinelle and Dunning used
plaster of paris as an impression material.
• 1848 : Gutta percha was introduced for making
impressions.
History of impression making

• In 1856 modelling plastic was introduced as
impression material.
• Impression methods were of open mouth variety.
Preiliminary impressions were made with
guttapercha/wax/modelling compound followed
by secondry impression made of plaster.
• 1866 AUSTIN stated plaster impression of the
lower jaw to be taken when theridges are well
defined ; but when the ridges are absorbed the
impression to be taken in guttapercha.
• 1866 FRANKLIN described corrected
impression
• 1869 GEORGE stated plaster was the impression
material of choice

• Muco-compressive type of impression making was
advocated by Green. It was known as “GREEN’S
ALL COUMPOUND TECHNIQUE”.
• The concept of muscle trimming was introduced.
• New impression materials were introduced.
1930- zinc oxide eugenol
1940- alginate
• 1933-Fish- DYNAMIC IMPRESSION METHOD-
Principal factor in mandibular denture stability.
• 1950 Rubber base impression
materials[ mercaptan, thiokol, polyether and
silicones] were introduced.

• IMPRESSION TECHNIQUES:
1. Turner and Campbell – advocated escape vent in
final impression tray to prevent buildup of
excessive pressure.
2. Stansberry – described negative pressure
technique.
3. Liberthal.R.H – introduced the closed mouth
impression technique.
4. Green.J.W – developed technique to handle
flabby ridges by recording it with impression
compound. Rationale behind it was that as the
patient functioned, the denture would move
forward, returning the tissues to original form
5 BOUCHER introduced a method of
impression technique- “SELECTIVE
PRESSURE TECHNIQUE”www.indianentalacademy.com

5.Richardson – advocated the capture of
flabby tissues in passive form.
6.H.L.Page – introduced the newer impression
procedure and the concept of
mucostatistics. The idea was to achieve
best possible adaptation of impression
material to tissue and to capture the
tissues in their passive undistorted form. It
was named as “MUCOSTATIC
TECHNIQUE” by Dr.Carrol.W.James.

BORDER MOULDING:
1. Pendelton, Swenson, Nagle, Sears, Heartwell
and Rahn introduced the method of border
moulding to capture anatomy of tissues related
to denture border.
2. Wilson.G.H described a method of
manipulating musculature against direction of
muscle fibres --- shortening of final denture
borders.
3. Green, Clapp, Campbell and Liberthal
described the act of sucking and swallowing
for border moulding.

Principles of Impression making.
• To cover the MAXIMUM possible
denture supporting AREA.
• To achieve the closest possible
CONTACT with the underlying
epithelium.
• To establish a PERIPHERAL SEAL.

Principles of Impression making.
• Preservation of the alveolar ridge
• Support
• Retention
• Stability
• Esthetics
PP
RR
EE
SS
SSwww.indianentalacademy.com

Preservation of the alveolar ridge
• DEVAN’S dictim
“it is more important to preserve
what already exists than to replace what is
missing”

Support
• Resistance to vertical forces of mastication
and to occlusal or the other forces applied
in direction toward the basal seat.
• Alveolar ridge and their covering mucosal
tissues becomes the area of the support.

• Areas of support
All the vestibular areas that provide
very little support but needed for
peripheral seal
Slight
Anterior ridges
and all ridge
slopes
Anterior ridges
and all ridge
slopes
Secondary
Buccal shelf
Posterior ridges
and retromolar
pad
Posterior ridges
and flat areas of
palate
Primary
Maxillary Mandibular

Techniques.
• Open mouth
– Mucocompres
sive
– Mucostatic
– Selective
pressure
• Closed mouth.
•Single stage
•Double stage

Closed mouth techniques.
• The denture has more accurate fit during
mastication.
• Impression material coated at bases of the blocks
and patient told to close in retruted contact
position.
• Patent given small amount of water to rinse.This
captures the normal movements of the surrounding
musculature.
• Material :
– thin zinc oxide eugenol,
– light body silicone.

Closed mouth technique.
• Drawbacks of
– Maxillary Disto buccal space is not recorded in
function.
– Viscous impression material can lead to increase in
vertical dimension.
Advantages
• Discrepancies in the jaw relations,
resulting from points of premature contact
of the rims are eliminated.
• Masseter muscle can be recorded in
function.
.

Mucodisplasive
• The impression material must be capable of
viscous flow as it is extruded under pressure
from between the tray and the tissue
surface.
• Materials used
– Impression compound
– High viscosity silicones
– Stiff zinc oxide eugenol.

Mucostatic.
• Use a very fluid impression material, and
use minimal pressure while it sets.

Selective pressure technique.
• It is a combination of extension for
maximum coverage within tissue tolerance
with light pressure or intimate contact with
the movable,loosely attached tissues in the
vestibules.
• The impression is refined with a minimum
of pressure.

SPECIAL IMPRESSION PROCEDURESSPECIAL IMPRESSION PROCEDURES
1. Controlled - Minimally displacive impression
techniques,
E.g. displaceable (flabby) upper ridge.
2. Controlled – Pressure impression techniques,
E.g. Fibrous / Knife edge / Unemployed lower ridge
3. Functional impressions,
E.g. Indeterminate peripheral extensions
4. Denture space impressions, (External impressions),
E.g. When the denture is subjected to excessive
displacing forces from surrounding musculature

Controlled - Minimally displacive
impression techniques
Patients wearing upper complete
denture opposed by lower natural
teeth.
Chronic complete denture wearers
Maxillary anterior ridge replaced by
fibrous tissue; reduced support for
dentures.
Patient complains of loose dentures
Impression techniques to avoid undue
tissue displacement.www.indianentalacademy.com

Controlled - Minimally displaciveControlled - Minimally displacive
impression techniques (Contd…)impression techniques (Contd…)
• Method AMethod A
– Special tray with a window cut in the
region of the displaceable tissue.

– Wash impression
with ZOE paste.
Border molding with
low fusing compound.

– Tray re-inserted, impression plaster
syringed over displaceable tissue.

Completed impression.

• Method BMethod B
– Special tray with a window cut in the region of
the displaceable tissue.
– Border molding with low fusing compound.

• Impression made with medium –
bodied / monophase elastomer.

• Light - bodied elastomer syringed over
window area.
• Dental plaster syringed over set, light - bodied
elastomer.

• Completed Impression

• Method CMethod C
– Special tray fabricated with no window.
– Border molding with low fusing compound.

• Impression made using ZOE paste / monophase
elastomer.
• When set, impression material corresponding to
displaceable tissue removed and tray perforated.

• Impression plaster / light bodied elastomer
syringed over displaceable tissue.
• Tray reseated and impression completed.

Controlled – Pressure impressionControlled – Pressure impression
techniquestechniques
• IndicatedIndicated
– Unemployed lower alveolar ridge unable to
provide acceptable support against vertical
loads and positive stability against lateral
forces.

Controlled – PressureControlled – Pressure
impression techniquesimpression techniques (Contd…)(Contd…)
• MethodMethod
– Primary impression made with alginate or
putty elastomer.
– Impression relieved over ridge crest area and
wash impression obtained with low viscosity
material. www.indianentalacademy.com

• Customized special tray with 2mm spacer
constructed.
• Spacer removed ; tray perforated in crestal
region .

• Low fusing compound used to obtain
impression of primary cast with special
tray.

• Impression reduced in the
region of buccal & lingual
sulci ; border molding
refined in patient’s mouth.
• Painful areas relieved.
• Tray re-insertion should
not result in pain.
• Impression completed with
light – bodied elastomer.

Functional impressionsFunctional impressions
• IndicationsIndications
– Reduced retentive forces ( Atrophic ridges )
– High displacing forces ( Uncontrolled muscle activity)
• Peripheral form molded by peri–denture
musculature.
• Existing denture utilized for the procedure.

• MethodMethod
– Tissue conditioning materials usually
employed for the procedures.
Functional impressionsFunctional impressions (Contd…)(Contd…)

• Impression surface & periphery of existing
denture reduced by 1.5-2mm to create space.
• Fitting surface of denture cleaned & dried.
• Material mixed & spread over fitting surface.

• Denture seated in patients mouth;
patient instructed to close in centric
occlusion.
• Patient encourage to perform functional
movements such as talking, swallowing,
smiling, to obtain a functionally
generated impression.

• Denture removed after 5 – 6 minutes ;Denture removed after 5 – 6 minutes ;
inspected and surplus material trimmed.inspected and surplus material trimmed.

• Patient returns after few / 24 hours;Patient returns after few / 24 hours;
impression inspected & cast poured.impression inspected & cast poured.

Denture space determinationDenture space determination
(External Impressions)(External Impressions)
• AimsAims
– To determine the space within which the
denture can be sited without being
subjected to excessive displacing forces
from the surrounding musculature.

Denture spaceDenture space
The portion of the oral cavity that is or may be
occupied by the maxillary and / or mandibular
denture (s).

Neutral ZoneNeutral Zone
• That area in the mouth, where, duringThat area in the mouth, where, during
functions thefunctions the forcesforces of the tongueof the tongue
pressingpressing outwardoutward areare neutralizedneutralized by theby the
forcesforces of the cheeks and lips pressingof the cheeks and lips pressing
inwardinward..
• Hence a possible zone of equilibrium

• IndicationsIndications
– Past denture looseness due to
powerful lower lip activity.
– Non-replacement of missing
teeth leading to tongue /
cheeks / lips partially
occupying the usual denture
space.
– Enlarged tongue,
E.g. Down’s Syndrome.
– Abnormal anatomy,
E.g. Hemimandiblectomy.
– Inability to wear a lower
denture
(Contd…)(Contd…)

How to record neutral zone?How to record neutral zone?
•    Generally done for lower
•    Done at any stage of CD fabrication
•    Materials used-Waxes,ZnOE,rubber
base putty, self-cure acrylic, impression
compound,tissue conditioners.www.indianentalacademy.com

• On accurate master casts, stabilized
denture bases are constructed.
• Wire loops embedded over ridge crest for
retention.

• Low fusing compound rims attached to
bases.
• Patient trained to perform a range of
functional movements such as smiling,
swallowing, speaking, etc.
• Compound rims softened and denture
bases inserted ; functional movements
carried out.

Recommended movementsRecommended movements
       Smile
   Swallow
   ‘ooh’
    ‘ah’

Denture space determinationDenture space determination(Contd…)(Contd…)

• Wash impression obtained with light – bodied
elastomer brushed on compound rims.
• Functional movements repeated.

• Plaster matrices constructed around records.
• Matrices guide in arranging & waxing teeth &
polished surfaces in optimum denture space.

• After wax trial is completed, external impressions
are obtained using ZOE paste / light – bodied
elastomer.

• PrecautionsPrecautions
– Stable record bases not interfering with muscle activity.
– Patient to be trained in molding procedure prior to insertion of
loaded tray.
– Excessive volume of molded material to be avoided – causes
distortion of potential denture space.
– External impression may be totally unlike the shape of a
“normal” denture, hence laboratory staff must be instructed
about reproduction of the recorded contours.

• Modifications of basic techniqueModifications of basic technique
– Determination of the optimal space for a
segment of a denture.
( E.g. The lower anterior region)
– Determination of the fit of the completed
denture to the potential space.

Determination of the optimalDetermination of the optimal
space for a segment of a denturespace for a segment of a denture
• Teeth & majority of the base
trimmed from appropriate
segment.
• Patient trained in molding
routine.
• Insert loaded tray in mouth,
mold while setting and
inspect after set.
• Re-insert in mouth and check
for stability.
• Matrices help to contour
teeth & base appropriately.

Determination of the fit of theDetermination of the fit of the
completed denture to the potentialcompleted denture to the potential
spacespace
• To detect interference to
normal muscle activity by an
existing denture.
• Coat low viscosity elastomer
on borders & polished
surfaces of denture.
• Denture inserted & molding
routine performed.
• Exposed denture base
indicative of interference &
corrected accordingly.www.indianentalacademy.com

Clinical finding Primary
impressions
Secondary
impressions
T echnique
Good ridge form Impression
compund
Plaster of
Paris, zinc
oxide/eugenol,
alginate or
elastomer
conventional
Sound denture
supporting tissues
No undercuts
As above but
undercuts
present
Impression
compound
Alginate or
elastomer;
depends on
degree of
undercuts
Impression technique
conventional but plan path
of insertion and removal of
tray to match that of the
proposed denture.
Suggested impression techniques.

Clinical findingClinical finding PrimaryPrimary
impressionsimpressions
SecondarySecondary
impressionsimpressions
TechniqueTechnique
Upper ridge
displaceable
Alginate Two - step technique Controlled minimally
displacive technique
Resorbed, fibrous,
lower ridge – pain on
palpation
Alginate / putty
elastomer
ZOE / light – bodied
elastomer wash on low
fusing compound
impression
Controlled pressure
impression technique
Atrophic ridges with
indeterminate
peripheral extensions
- Functional molding
with tissue conditioners
Existing denture
modified & material
molded by functional
movements
Resorbed ridges
with hyper active
musculature
Impression
compound / alginate /
putty
1.ZOE / monophase
for master
impression.
2.Low fusing
compound / tissue
conditioner / light
bodied elastomer /
resin for external
impression.
Denture Space
determination done
by external
impressions for
contour of polished
surfaces

Impression procedures for compromised ridges/cosmetic dentistry courses

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