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1. SPECIAL IMPRESSION
PROCEDURES FOR COMPRISED
CLINICAL CONDITIONS
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. AIMS
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 maintainwww.indiandentalacademy.com
health of the oral tissues
3. PRINCIPLES
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.
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4. SPECIAL IMPRESSION PROCEDURES
1.
Controlled
techniques,
-
Minimally
displacive
impression
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
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5. 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.
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6. Controlled - Minimally displacive
impression techniques (Contd…)
Method A
Special tray with a window cut in the
region of the displaceable tissue.
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7. Controlled - Minimally displacive
impression techniques (Contd…)
Border molding with
low fusing compound.
Wash impression
with ZOE paste.
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10. Controlled - Minimally displacive
impression techniques (Contd…)
• Method B
– Special tray with a window cut in the region of
the displaceable tissue.
– Border molding with low fusing compound.
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11. Controlled - Minimally displacive
impression techniques (Contd…)
Impression made with medium –
bodied / monophase elastomer.
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14. Controlled - Minimally displacive
impression techniques (Contd…)
Method C
Special tray fabricated with no window.
Border molding with low fusing compound.
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15. Controlled - Minimally displacive
impression techniques (Contd…)
Impression made using ZOE paste / monophase
elastomer.
When set, impression material corresponding to
displaceable tissue removed and tray perforated.
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17. Controlled – Pressure impression
techniques
Indicated
Unemployed lower alveolar ridge unable to
provide acceptable support against vertical
loads and positive stability against lateral
forces.
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18. Controlled – Pressure
impression techniques (Contd…)
Method
Primary impression made with alginate or
putty elastomer.
Impression relieved over ridge crest area and
wash impression obtained with low viscosity
material.
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19. Controlled – Pressure
impression techniques (Contd…)
Customized special tray with 2mm spacer
constructed.
Spacer removed ; tray perforated in crestal
region .
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20. Controlled – Pressure
impression techniques (Contd…)
Low fusing compound used to obtain
impression of primary cast with special
tray.
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21. Controlled – Pressure
impression techniques (Contd…)
Impression reduced in the
region of buccal & lingual
sulci ; border molding
refined in patient’s mouth.
Painful areas relieved.
Tray re-insertion
not result in pain.
should
Impression completed with
light – bodied elastomer.
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22. Functional impressions
Indications
Reduced retentive forces ( Atrophic ridges )
High displacing forces ( Uncontrolled muscle activity)
Peripheral form molded by peri–denture
musculature.
Existing denture utilized for the procedure.
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24. Functional impressions (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.
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25. Functional impressions (Contd…)
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.
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28. Denture space determination
(External Impressions)
Aims
To determine the space within which the
denture can be sited without being
subjected to excessive displacing forces
from the surrounding musculature.
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29. Denture space
The portion of the oral cavity that is or may be
occupied by the maxillary and / or mandibular
denture (s).
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30. Neutral Zone
That area in the mouth, where, during
functions the forces of the tongue
pressing outward are neutralized by the
forces of the cheeks and lips pressing
inward.
Hence a possible zone of equilibrium
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31. Denture space determination
(Contd…)
Indications
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
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32. Denture space determination
(Contd…)
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.
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33. Denture space determination
(Contd…)
On accurate master casts, stabilized
denture bases are constructed.
Wire loops embedded over ridge crest for
retention.
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34. Denture space determination
(Contd…)
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. www.indiandentalacademy.com
37. Denture space determination
(Contd…)
Wash impression obtained with light – bodied
elastomer brushed on compound rims.
Functional movements repeated.
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38. Denture space determination
(Contd…)
Plaster matrices constructed around records.
Matrices guide in arranging & waxing teeth &
polished surfaces in optimum denture space.
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40. Denture space determination
(Contd…)
After wax trial is completed, external impressions
are obtained using ZOE paste / light – bodied
elastomer.
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41. Denture space determination
(Contd…)
Precautions
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.
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42. Denture space determination
Modifications 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.
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43. Determination of the optimal
space 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.
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44. Determination of the fit of the
completed 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.
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45. In a Nut Shell…
CLINICAL FINDING
PRIMARY
IMPRESSIONS
SECONDARY
IMPRESSIONS
TECHNIQUE
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.
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Denture Space
determination done
by external
impressions for
contour of polished
surfaces