1. Good Morning

2. Prof. Dr. Manal A. El Ebiary
Dental Bio- Materials Department
Faculty of Dentistry
Tanta & MUST Universities

3. Impression Materials

4. Definition
substances used for recording the form and dimensions of the oral tissues
They are used to record a negative replica to teeth and/or supporting tissues

5. Material is introduced in the mouth in a plastic condition
to set against the oral tissues.
It is then removed from the mouth when hardened. 2 1 3 4 6 5

6. The set impression is a negative reproduction
of the oral tissues.
A positive reproduction is obtained by
pouring a suitable model or die material into it.

8. 1. Accuracy:
a restoration or an appliance fabricated in the laboratory cannot be more accurate than the impression from which the used model is prepared.

9. 2. Biologically acceptable:
non-toxic
non-irritant
acceptable odor and taste.

10. 3. It should not be affected by the oral fluids.
4. Easily manipulated, with minimal equipment.
5. It should have a suitable working time to allow for placement of the impression material in the tray and then insertion of the tray into the mouth before beginning of hardening

11. Accuracy of the impression materials

12. 1- High flow at the beginning, i. e
1- High flow at the beginning, i.e. the material must be in a fluid or plastic state on insertion into the mouth, to record fine details.
2. Dimensionally accurate: should not expand, contract or warp during setting.
3. Dimensionally stable: on storage of the impression in the dental laboratory before pouring the cast

13. 5. During removal from the mouth, it should be
4. Should be elastic on removal from the mouth so that undercuts can be recorded without distortion of the impression.
5. During removal from the mouth, it should be
adherent to the tray.
6. Compatible with the gypsum products: not need a separating medium.

14. Classification of Impression Materials
Behaviour after setting
Uses
Manner of setting

15. I-According to manner of setting
1) Chemical (irreversible):
plaster impression,
zinc oxide eugenol,
alginate
rubber base
2) Physical (reversible):
agar agar,
impression compound
impression waxes.

16. II- Behavior after setting

17. Depending on their ability to regain their original shape after removal from the undercuts.
1. Inelastic
wax
Plaster of Paris,
ZnO/eugenol and
impression compound.
2. Elastic
hydrocolloids and
rubber impression materials.

18. Plaster of Impression Zinc oxide
Impression Materials
Inelastic Elastic
Plaster of Impression Zinc oxide
Paris compound eugenol
Hydrocolloids Elastomers
Agar Agar Alginate
Polysulphide Silicones Polyether
Condensation Addition

19. III- According to uses Edetulous Patient Partialy edentulous patient
Plaster, impression compound and Zinc oxide and eugenol, hydocolloids, rubbers
Hydocolloids, rubbers

21. According to the Accuracy
1ry Impression (stock tray)
2ry Impression (special tray)
Compound impression material
Plaster impression material
Zinc oxide/eugenol impression material
Alginate impression material
Agar Agar impression material
Rubbers impression materials

22. Plaster of Paris
powder
Water

23. 1-  - CaSO4.1/2H2O; not α and/or improved stone
Weaker: So it will break during removal from the undercut and thus avoids injury to the patient and the fractured part can be reassembled accurately.
Higher W/P ratio, which increases the flow at the beginning and thus records fine details.
Less exothermic heat evolved during taking of the impression.

24. 2. Modifiers:
** 4% K2SO4 decreases the setting expansion and the setting time
→ ** 1% borax as a retarder

25. 3. Natural gums:
Improve its handling characteristics. They increase its cohesion and facilitate border molding of the impression.
4. Flavoring agent:
More acceptable to the patient, through agreeable taste.

26. 5. Coloring materials:
Distinguish the impression from the cast, which will also be made of gypsum products.
6. Potato starch:
To obtain the soluble plaster. After the impression is cast and hardened, it is soaked in hot water and the starch swells and the impression disintegrates and will be easy to remove.

27. Accuracy of plaster impression :
a. Material is semi-fluid when inserted into the mouth it has excellent recording of the fine details.
b. The dimensional changes on setting in the mouth are negligible due to anti-expansion additives.

28. separating medium should be used
c. A plaster impression fractures on removal from undercuts and can be reassembled.
e. Elasticity: Being inelastic, it will not record the form of the under cut.
separating medium should be used
The use of a separating medium is considered a disadvantage since fine details might be obliterated.

29. Non elastic impression materials Assoc. Prof. Dr. Manal
Impression Compound
Non elastic impression materials Assoc. Prof. Dr. Manal

30. Impression Compound Prof. Dr. Manal A. El-Ebiary
Type (I) Low fusing
Impression Compound Prof. Dr. Manal A. El-Ebiary

31. Impression Compound Prof. Dr. Manal A. El-Ebiary
Type ( II) high fusing
Impression Compound Prof. Dr. Manal A. El-Ebiary

32. Application:
1. Full jaws impression in edentulous mouth.
2. Impression trays
3. Peripheral seal materials.
4. Single impression with copper band for inlays and crowns.

34. Impression Compound Prof. Dr. Manal A. El-Ebiary
Composition
Thermo-
plastic
Filler
plasticizer
Impression Compound Prof. Dr. Manal A. El-Ebiary

35. Thermoplastic material: e. g. Natural resins and waxes
Thermoplastic material: e.g. Natural resins and waxes. They soften by heating and give the qualities of flow and cohesion.
2. Fillers: e.g. Talc, soapstone or diatomaceous earth. They add body and give a suitable working consistency.
3. Plasticizers: e.g. Stearic acid or stearin. These act as lubricants and together with fillers control the flow and consistency of the material.
4. Coloring agents: e.g. Rouge. It produces characteristic reddish brown color most commonly used. Black and green colors are also available.

36. Types
Low fusing
High fusing

37. Type (I ) low fusing compound

38. A- For recording prosthetic impressions: Such as preliminary impressions of edentulous patients, supplied in sheets
about 4-5 mm thick.
B- Peripheral seal materials.
C- copper band impression for inlay and crown

40. Type (II) high fusing compound
Used as tray materials, which are sufficiently rigid to support other impression materials (wash impression).

41. Properties

42. Dimensional stability
Accuracy
Flow
Dimensional stability

43. not sufficiently fluid to record all the fine details.
Type (I) materials is 85% at 45ºC but less than 65 at 37ºC,
Type (II) materials is 70% at 45ºC but less than 2% at 37ºC.

44. 2- shrinkage occurs on cooling from high temp. to mouth temp..
Causes of dimensional changes:-
1- High coefficient of thermal expansion.
2- shrinkage occurs on cooling from high temp. to mouth temp..
3- Shrinkage occurs on cooling from mouth to room temperature ( %).
Heating the surface of the set material in a flame and remaking the impression minimizes the actual magnitude of the contraction.

45. 4- Distortion:- Stresses can be set up within the material, subsequently distortion can occur during storage of an impression due to relief' of these stresses. Then the impression should cast within an hour.
5- The material is non-elastic the most serious drawback of this material is that it drags and distorts when being removed from an undercut area.

46. compatible with model and die materials and do not need a separating medium.
Conductivity: Compound has poor thermal conductivity Time must be allowed during either heating or cooling to allow the dental compound to come to a uniform temperature.

47. These impression can be removed from the mouth, re-softened and reinserted for any corrections required..
Accept additions to the impression
Can be electroplated with copper.

48. Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary

49. Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary

50. One paste called the base paste
Zinc oxide 80%.
Inert oil 15% to form a paste.
Hydrogenated resin.

51. Second paste called the accelerator contains:
Oil of cloves or Eugenol 12-15%. Oil of cloves: Sometimes used instead of the eugenol, since it is less irritant than eugenol.
Gum rosin and oils 65%: Gives body and coherence and imparts thermoplastic properties to the set materials for easy removal from the cast by softening it in hot water.
Filler talk or kaolin or diatomaceous earth to form a paste.

52. Moisture. A very slight amount of moisture water is added to the zinc oxide parts or accelerator, since it is essential for the hydrolysis of the zinc oxide to its hydroxide
Accelerator
* Mg chloride
* Zn acetate

53. Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary
Manipulation
Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary

54. Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary

55. Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary

56. Zinc oxide eugenol impression Prof. Dr. Manal A. El-Ebiary

57. Setting Reaction: Zn O + H2O → Zn (OH)
Zn (OH) Eugenol → Zn Eugenolate +H2O (Base) (Acid) (Salt) Chelation Reaction
Without H2O, i.e. if eugenol is completely dehydrated before mixing with ZnO powder, the resulting paste will not harden.

58. Factors affecting setting time
Ratio between Z.O. and eugenol, increase in the paste which contain accelerator leads to fast setting reaction.
Longer mixing time leads to shorter setting time.
Cooling spatula, glass slab leads to prolong setting time.
Addition of few drop of water will accelerate the reaction and decrease the setting time

59. 5-Addition of inert oil, waxes, tertiary alcohol leads to prolong setting time but it reduces the rigidity and produce inhomogeneous mass.
6- The smaller particles size the smaller surface area the faster the reaction and shorter setting time.
7- Type I (hard) characterized by rapid setting. While type II (soft) characterized by slow setting.

60. Properties

61. Accuracy of zinc oxide and eugenol:
Flow: Very accurate as they are sufficiently fluid to record the fine details in the mouth.
b. Dimensional accuracy and stability:
** No or very little dimensional change on setting.
** No dimensional change during storage of the impression.
c. Elasticity: inelastic, it will not record the form of the undercut.

62. d. Compatibility with the die material: It is removed from the model by softening in hot water at 60ºC.
e. Eugenol can be irritant, giving a tingling or burning sensation to the patient and leaves a persistent taste, which may be unpleasant to some patients.
N.B. Non-eugenol zinc oxide impressions are now available to avoid such effect.
h. The impression paste can adhere to tissues,