Sp.imp.procedures./ dentistry dental implants/ dentistry dental implants

SPECIAL IMPRESSIONSPECIAL IMPRESSION
PROCEDURES FOR COMPRISEDPROCEDURES FOR COMPRISED
CLINICAL CONDITIONSCLINICAL CONDITIONS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

AIMSAIMS
To customize the denture bases to the
supporting tissues
To develop the functional border of the
denture
To enhance retention & stability
To obtain optimal esthetics
To maintain health of the oral tissues

PRINCIPLESPRINCIPLES
Denture base should cover maximum possible
supporting area.
Impression surface should achieve closest
possible contact with underlying tissues.
Border form of the prosthesis should establish
a peripheral seal ; support lips and cheeks
functionally and esthetically.

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.

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.

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.

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.www.indiandentalacademy.com

Determination of the fit of theDetermination of the fit of the
completed denture to the potential spacecompleted denture to the potential space
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.

In a Nut Shell…In a Nut Shell…
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

Sp.imp.procedures./ dentistry dental implants/ dentistry dental implants

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