Impression Materials Part - 3 - Dental Materials

This is the 3rd part of the series on Impression materials. It delves deeper into the non-rigid impression materials. They are broadly classified as aqueous and non-aqueous. The aqueous includes the alginates, which is irreversible and agar, which is reversible. Under the non-aqueous, we have polysulfides, polysilicones and polyether. The polysilicones are further classified into addition silicones and condensation silicones while polyethers are classified based on whether they are chemically activated or light activated. Do go through the presentation for a better understanding of the properties of agar and alginate impression materials.

1. Impression materials part- 3 Dr. Shiva

2. RECAP

3. Ada specification no Filler plasticizer Dispensing composition Manipulation Factors effecting setting time Properties Classification Chemical reaction Advantages Disadvantages Uses modifications

4. 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.

5. 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.

6. 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.

7. 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.

8. Mechanism of Gelation & liquefication

9. Mechanism of Gelation & liquefication

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

11. Syneresis

12. Syneresis

13. Imbibition

14. Difference b/w syneresis and Imbibition

15. 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.

16. AGAR IMPRESSION MATERIAL (REVERSIBLE HYDROCOLLOID) ADA Specification Number: 11

17. Gelation and liquefication

18. Composition

19. 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

20. Impression techniques Wet Field Technique Laminate technique

21. Wet field technique

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

23. Irreversible Hydrocolloids/ ALGINATE ADA no: 18

24. Calcium alginate Trisodium phosphate

25. Trisodium phosphate Sodium Alginate Calcium sulphate

26. Calcium alginate Trisodium phosphate

27. Composition

28. Manipulation

29. 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

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

31. Laminate Technique 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.

32. Laminate Technique

33. This reaction is know as???

34. Thank you drshivasai

35. Mind mapping