very simple presentation

1. Problems encountered in dental
impressions and their impact
on final restoration

2. Introduction
Prerequisites
Impression material
Impression techniques
Impression tray
Impression errors
ILOs

3. Dental impression is defined as the
negative imprint of the teeth and other
parts of the oral cavity (gums, surrounding
tissues, etc.)
Preliminary impression: for the diagnosis,
documentation of dental arches, and as a
visual aid for education.
Definition
of Dental
Impression
Final impression: used to make casts and
dies with the precise details of the tooth
structures and their surrounding tissues.
Bite registration: to document the occlusal
relationship between arches.

4. PREREQUISITES
1- Tissue Heath
– Periodontal disease
must be treated and
resolved before fixed
prosthodontic
treatment.

5. PREREQUISITES
2- Saliva Control
– Rubber dam is probably the most
effective method.
– Absorbent cotton rolls.
– Saliva ejector must be placed
where the saliva pools.

6. 2- Saliva Control
– Svedopter (left) and
Speejector (right)
saliva evacuators.
– disposable
Hygoformic aspirator
system.

8. PREREQUISITES
3- Displacement of
Gingival Tissues
– Mechanical displacement:
retraction cord.
– Chemicals: aluminum
sulfate or epinephrine
cause localized soft tissue
shrinkage.
– Surgical tissue removal:
curettage, excision with a
scalpel, electrosurgery, or
laser.

10. Impression
Materials

11. Impression
Materials
- Polysulfide:
• Has unpleasant sulfide odor and long setting
time in the mouth (about 10 minutes) .
• Has better dimensional stability and tear strength
and it is the least expensive elastomer .
- Condensation Silicone:
• is its relatively short setting time in the mouth
(about 6 to 8 minutes) and it is odorless , putty
wash technique is used .
• Hydrophobic so the prepared teeth and gingival
sulci must be completely dried , Silicone and
polysulfide have a dimensional instability.

12. Impression Materials
- Addition Silicone:
• Hydrophobic
• One disadvantage of some of these materials is that
setting can be inhibited by latex gloves or by interim resin
materials ,The problem is most apparent if a hand-mixed
putty .
• it has high dimensional stability , accuracy , elastic
recovery .
- Polyether:
• Dimensional stability is excellent as there is no byproduct
and its polymerization shrinkage is unusually low .
• short setting time in the mouth (about 5 minutes)
• The stiffness of the set material causes problems when a
stone cast is separated from the impression.

13. Impression Techniques
- Heavy-bodied–Light-bodied Combination.
- Single-mix Technique.
- Automix Technique.
- Machine Mixing Technique.
- One step Putty wash technique.
- Two step Putty wash technique.
- Modified one step putty wash technique.
-Closed-mouth Impression Technique.

14. Selection of impression
material
➢ Selection of impression material according to
case.
➢ The best impression material for veneers ,
implant is polyvinyl siloxane material with
Automix Technique .
➢ The best impression materials for custom made
post is polyvinyl siloxane with Automix
Technique.
➢ condensation silicone used with crown , bridge ,
implant and over denture (Putty wash
technique )

15. Impression
Trays
– Prefabricated or Custom.
– Autoclavable or
Disposable.
– Perforated or
Nonperforated.
– Metallic or Plastic.

16. Impression
Errors
– 1- Inadequate Marginal Detail
– 2- Internal Bubbles
– 3- Marginal Tears
– 4- Inadequate Impression Material Mixing
– 5- Inadequate Syringe Material
– 6- Tray Selection
– 7- Separation from the Tray
– 8- Tray Distortion
– 9- Surface Contamination
– 10-rotation
– 11-Dimensional instability due to wrong disinfection
– 12-Dimensional instability due to wrong storage

17. 1- Inadequate
Marginal Detail
- Voids at the margins are the result
of either insufficient retraction or
fluid accumulation that prevented
the impression material from flowing
around the margin.
– Solved by:
– 1-using retraction cord with
syringeable hemostatic or
retraction paste that placed into
gingival sulcus after preparation.
– Lead to: open margin and
inadequate marginal fit.

18. 2- Internal
Bubbles
– causes: occur as a result of either fluid
accumulation or air entrapment.
– solved : 1-flushing and drying of the preparation
prior to impression taking and using hemostop .
– 2-Placing a curved intraoral impression tip into
the deepest part of the preparation floor , it will
force air out of the preparation and decreasing
entrapment.
– The fit of final restoration will not be affected by
air bubbles but if there is fluid voids are larger
enough to affect the long term success of luting
agent , The prosthetic material may also be
thinner than recommended.

19. 3- Marginal
Tears
– causes: -Removal of the impression prior
to complete setting of the syringeable
material.
– Inadequate mix.
– using a syringeable PVS in a thin deep
sulcus.
– solved by: 1-any remnants of the original
impression material must be removed
from the sulcus.
– 2-using more viscous syringeable material
– 3-using retraction cord or retraction
paste.
– Retake impression

20. 4-Streaking
– Causes:1- improper amounts of base and
catalyst
– 2-Glove contamination
– 3-Inadequate mixing
– more common with hand mixed putty
materials.
– Lead to: streaking in impression

21. 5- Inadequate
Syringe
Material
– A “stepped” impression may
result when using a two-phase
impression technique.
– This can be avoided by filling
the entire set tray material
where the teeth depressions
are with syringeable material,
to provide a uniform
impression.
– The result is restorations that
require excessive occlusal
adjustments.

22. 6- Tray Selection
– Cause:
– A tray that is too narrow may prevent
adequate seating of the tray
– solved by:
– make sure that tray cover all surfaces of teeth.
– it’s important to select a tray that is long
enough to capture the entire arch from the
hamular notches or retromolar pads to the
most anterior aspect of the buccal vestibule. -
the width of the selected tray is also important
– lead to missing of needed arch detail.

23. 7- Separation
from the Tray
– Cause:
– This deformity may be overlooked
when using trays with slots and
holes to lock the impression
material.
– Solve by:
– Tray adhesive should be used with
all impressions to help eliminate
impression separation from the
tray.
– Retake impression

24. 8- Tray Distortion
– is more common with dual arch trays due to
their more flex
– Solved by:
– Two-phase impressions can be used to
create a custom format using the triple tray.
The preliminary impression creates a rigid
base that will provide hydraulic pressure to
force the syringeable material in and around
the preparations.

25. 9- Surface
Contamination
Causes :
– 1-leaving remnant of material on tooth surface as
composite - or remnant of temporary crown material .
– 2- presence of some blood on tooth after preparation .
– solved by :
– 1-rinse the prepared are with water well and remove
any remnants then dry well all surfaces of teeth .
– 2-use hemostatic agents to stop bleeding then dry well .
– 3-Disinfection of impression by Immersion of the
impression in common disinfecting solutions (e.g.,
phenols and glutaraldehyde) for periods of up to 60
minutes

26. 10-Rotation
– Cause :
– Lack of adhesive or wrong
application of tray in mouth .
– Lead to inaccurate seating of the
tray.

27. 11-Dimensional instability
due to wrong disinfection
– Disinfection does not affect the accuracy or
surface reproduction of the elastomer.
– Suitable chemicals should be used for
disinfection, such as glutaraldehyde solutions
not less than 30 min.
– polyether or “hydrophilic”addition silicone
impression materials should be sprayed and
stored in a plastic bag rather than submerged
and soaked in a glutaraldehyde solution
Because of its tendency to distort and absorb
moisture.

28. 12-Dimensional instability
due to wrong storage
FOR (POLYSULFIDE- CONDENSATION SILICONE
POLYMERIZATION REACTION OF ELASTOMERS
NEVER COMPLETE IT CONTINUE AT LEAST TO
24 H AFTER CLINICAL SET THIS MEANS MORE
SHRINKAGE WILL OCCUR.
– POLYETHER- ADDITIONAL SILICONE
)IMMEDIATE POURING IS RECOMMENDED
AFTER THE GRADUAL RECOVERY WITHIN 1
HOUR.

29. REFERENCES
– Contemporary Fixed Prosthodontics (5th edition).
– Kurtzman, G., Mahesh, L., & Strassler, H. E. (2012).
Dental Impressions: Identification and Correction of
Common Problems. Indian J Dent Res, 1(1), 13-17.
[cited 2020May2]. Available from:
http://jrdindia.org/ver2/app/upload/Review
Article.pdf
– [cited 2020May2]. Available from:
https://www.slideshare.net/talibamin5/modified-one-
step-putty-wash-technique
– [cited 2020May2]. Available from:
https://www.ultradent.com/products/categories/retra
ction

30. “Whatever you do, do it well”
Walt Disney
Thank you