DLA 1201, exam 6

1. Astringents,
Inelastic Impressions,
Digital Impressions

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

8. Retraction Cord

9. Retraction materials

10. After Removal of retraction

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.

19. What’s wrong with this impression?

20. What’s wrong with this impression?

21. Final impression

22. Final impression

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.

25. Digital impressions

26. Advantages…

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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