The document discusses various types of impression materials, focusing on rigid and non-rigid options such as impression compounds, alginate, and agar. Key concepts include the classification of materials, their properties, manipulation techniques, advantages and disadvantages, as well as the gelation process. Additionally, it covers applications in dental impressions and specific techniques used in the field.

1. IMPRESSION MATERIALS
PART-3
Dr. Shiva

2. RECAP

3. Rigid impression materials
Impression
compound
Green stick Zoe
• Ada specification no
• Filler
• plasticizer
• Dispensing
• composition
• Manipulation
• Factors effecting
setting time
• Properties
• Classification
• Chemical reaction
• Advantages
• Disadvantages
• Uses
• modifications

4. Impression material
Rigid Non rigid
Aqueous
Irreversible
(Alginate )
reversable
(Agar agar )
Non aqueous
Polysulfides Polysilicones
Addition
silicones
Condensation
silicones
Polyether
Chemically
activated
light
activated

5. Aqueous Elastic Impression Materials
• True Solution
• If the size of the dispersed particles is
small (less than 10-7 cm) and cannot be
seen by naked eye or through a
microscope, the system is termed as true
solution, e.g. sugar solution.

6. Suspension and Emulsion
• If the size of the dispersed particles is large
(more than 10-4 cm) and can be seen by
naked eye or through a microscope, the
system is termed as suspension or
emulsion. Suspension: Solids dispersed in
liquids, e.g. sand in water. Emulsion:
Liquids dispersed in liquids, e.g. oil and
water.

7. Colloids
• The term colloid is used to describe a state
of matter in which the matter is divided into
particles of size between 10-7 cm to 10-4 cm
and distributed in another medium. Colloids
are often classified as fourth state of matter.

8. • Sol
• A colloidal system in which the dispersed phase is a solid and dispersion medium is a
liquid
• . Gel
• A heterogeneous biphasic system in which a liquid is dispersed in a solid dispersion
medium is known as gel.
• Gelation
• Gelation is a process of conversion of viscous liquid sol into a semisolid jelly-like
substance (sol → gel). It is a solidification process and brought about by either a physical
change or a chemical reaction.The temperature at which a sol converts to a gel (in case
of reversible hydrocolloids) is known as gelation temperature.

9. Mechanism of Gelation & liquefication

10. Mechanism of Gelation & liquefication
The aggregates of molecules are dispersed
sol form.
agglomerate together
chains or fibrils or micelles.
This fibril network encloses the dispersion medium
branch and intermesh
joined together
gel

11. Hysteresis
• The temperature lag between the gelation temperature
and liquefaction temperature of a gel is known as
hysteresis.

12. Syneresis

13. Syneresis

14. Imbibition

15. Difference b/w
syneresis and
Imbibition

16. Remedy
• In order to ensure optimum accuracy the model should be cast as soon as possible.
If it is not possible to pour it up immediately it can be stored in 100% relative
humidity for not more than 1 hour. For shorter periods the surface of the
impression can be covered with damp napkin.

18. AGAR IMPRESSION MATERIAL
(REVERSIBLE HYDROCOLLOID)
• ADA Specification Number: 11
Dispension
Tray
material
Syringe
materials

19. Gelation and liquefication

20. Composition

21. Manipulation
1.Liquefaction of Gel
(Gel to Sol) 100°C
3.Conditioning or
Tempering 43°–45°C
2.Storage of the Sol
63°C to 66°C

22. Impression techniques
•Wet FieldTechnique
•Laminate technique

23. Wet field
technique

24. Uses of Agar
• For dentulous impressions.
• For crown and bridge impressions to a limited extent.
• For model duplication.

25. Advantaged
• Reproduces finer details.
• model duplication.
• Sufficiently flexible.
• High elastic recovery.
• Can be reused.
Disadvantages
• Dimensional instability.
• Impression cannot be
electroplated.
• Low tear strength.
• Elaborated and expensive
equipment is required for
manipulation.

26. Irreversible Hydrocolloids/ ALGINATE
•ADA no: 18 ALGINATE
Type – I
Fast set
Type – II
Normal
set

28. Calcium alginate
Trisodium phosphate

29. Trisodium phosphate
Sodium Alginate
Calcium sulphate

30. Calcium alginate
Trisodium phosphate

31. Composition

32. Manipulation

33. Advantages
• Reproduces excellent
surface detail.
• High elastic recovery.
• Record undercuts.
• Comfortable to the patient.
• It is hygienic since fresh
material is used each time.
• It is inexpensive.
Disadvantages
• Dimensionally unstable.
• Low tear strength.
• Cannot be electroplated.
• No proper storage medium.
• Cannot be added if faulty

34. Uses
• Used for making the impressions of edentulous and partially
edentulous mouths.
•To a limited extent in making the impressions of inlay, crown and
bridges.
• In orthodontics, it is used to take the impression of the patient’s
mouth prior and during the treatment to construct study models

35. Modified Alginates
• Dust-free or Dust-less Alginates
• Siliconized Alginates
• Modified by the Addition of Chemical Indicators
(chromatic alginate)
• Alginates Containing Disinfectants

36. LaminateTechnique
• In this technique, the Agar material is injected onto the prepared
teeth and alginate in an impression tray positioned over it. Alginate
gels by a chemical reaction whereas Agar gels by means of contact
with cooler alginate rather than circulating water.The impression may
be removed in about 4 minutes.

37. LaminateTechnique

38. This reaction is
know as???

39. Thank you
drshivasai

40. MIND MAPPING