2. Components of Impression Making for
Crown and Bridge Procedures
Gingival retraction
Methods of retraction
Retraction cord
Astringents/hemostatic agents
Two-cord retraction technique
Evaluation of cord placement
Evaluation of retraction
Retraction paste, silicone, or gel
Making the impression
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3. Components of Impression Making for
Crown and Bridge Procedures
Dental assistants and hygienists frequently are involved in the
impression making process.
Those that are licensed in expanded functions may actually
pack retraction cord, use astringents, and make the
impressions for crowns and bridges.
4. Components of Impression Making for
Crown and Bridge Procedures
The objective of gingival retraction is to provide a space
in the gingival sulcus of adequate dimensions to receive
the impression material around the entire margin.
5. Astringents/hemostatic agents
Astringents are topically applied chemicals that
constrict tissues and are useful in gingival
retraction.
They also constrict the small blood vessels and
produce mild coagulation of blood, so they are
also used as hemostatic agents.
6. Astringents/hemostatic agents
The two most common astringents are:
Aluminum Chloride
Hemodent, gigiAid, VisoStat
Ferric sulfate
Astrigedent, ViscoStat
A less used astringent is Racemic Epinephrine
Can spike blood pressure
Increase heart rate
Dangerous for patients with hypertension or cardiac problems
This is a………………..for use??????
7. Astringents/hemostatic agents
Can adversely effect the surface detail of a
PVS impression
Ferric sulfate may also interfere with the set
of materials
Astringents should be washed off the tooth
before applying the wash material
11. Components of Impression Making for Crown
and Bridge Procedures
Evaluating the impression
Rinse to remove blood, saliva, and debris
Ask the following questions:
1. Did the impression capture all teeth and tissues needed for the
impression?
2. Can I see the preparation clearly?
3. Is the margin visible clearly all the way around the tooth?
4. Has the impression captured a little bit of the unprepared tooth
just beyond the margins?
12. What’s wrong with this impression?
A large void is
present in the wall of
the molar.
The adjacent
premolar impression
has shiny rounded
margins lacking
detail from
contamination with
blood.
13. What’s wrong with this impression?
A portion of the margin
is missing
14. What’s wrong with this impression?
The bottom cord from a
two-cord technique was
not packed apical to the
margin an dis caught in
the impression of the
margins
15. What’s wrong with this impression?
The set impression
material has
separated from
the tray, likely
from inadequate
tray adhesive
16. What’s wrong with this impression?
Facial (left molars)
and lingual (right
molars) and premolar)
pulls of material.
Syringe material was
starting to set before
the tray was seated.
17. What’s wrong with this impression?
Nothing. This is a clear
impression with “flash,”
no voids, and fine detail.
Adjacent structures are
also captured well.
18. What’s wrong with this impression?
Nothing. The bottom
cord has been
retained in the
impression, but is not
sitting on the
margins. Good detail,
no voids, and “flash”
is present at the
margins.
23. Digital impressions
The digital impression removes many of the
requirements needed for traditional impressions.
Complete and stand-alone intraoral scanners are
available.
24. Digital Impressions
There is no need for trays, adhesive, disinfectants, pouring
impressions, and packaging impressions for transporting to
the laboratory.
A big advantage is the ability of the clinician to view the
preparation magnified on a computer monitor and see it
from multiple angles by rotating the image.
The images can be reviewed and retaken if needed.
27. Disadvantage to the digital
impressions
A major disadvantage to the digital impressions is the
significant cost involved in purchasing a digital scanner and
some training and practice that is needed to efficiently operate
it.
$12,000-$60,000
https://youtu.be/qndzT5qm4NY
28. Inelastic Impression Materials
Four types
Dental impression compound
Impression plaster
Zinc oxide eugenol impression material
Impression wax
The inelastic impression materials are among the
oldest impression materials used in dentistry and
are seldom used in today’s practice.
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29. Disinfecting Impressions
Impressions are potentially infectious.
They must be disinfected before being handled in the
office laboratory or sent to a commercial laboratory.
Disinfection of impressions should begin in the
operatory with a disinfected appropriate for the
impression material being used.
Follow manufacturer’s recommendations for
disinfecting the impression materials.
30. Disinfecting Impressions
On rare occasions, it may be necessary to
disinfect the cast produced from an
impression.
Casts should be completely set for a
minimum of 24 hours prior to disinfection
and should not be immersed in disinfecting
solutions.
31. Disinfecting Impressions
Impression trays must be cleaned and
sterilized or disinfected after their use or
after being tried in a patient’s mouth.
Disposable trays should not be disinfected or
sterilized for subsequent uses.
32. Summary
Impressions are an integral part of the
procedures needed for delivering comprehensive
care to patients
Impressions are made daily, and the various
impression materials must be understood by the
clinician for correct selection, manipulation, and
disinfection of the materials and for pouring of
casts.
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