chapter five impression compound.pptx

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1. Impression material and gypsum products Chapter 5

2. Impression materials

3. Main contents Definition Advantages Properties Impression compound Zinc oxide- eugenol Gypsum

4. Definition A dental impression material is a negative record of the tissue of the mouth. The negative reproduction of the tissue given by the impression material is filled up with dental stone or other model materials to get a positive cast. it is used to reproduce the form the teeth and the surrounding tissues.

5. Negative Reproduction Positive Reproduction

6. Die is The positive reproduction of a single tooth cast or model it is when several teeth or a whole of the arch is reproduced , called

7. Advantages of using a cast or model 1) models provide a three-dimensional view of the oral structures . 2)Many restorations or appliance are best constructed on a cast. 3) Saving valuable clinical time

8. 4)They serve as treatment records Before After

9. Desirable properties of an impression materials Biocompatible to the dentist and patient Acceptable to the patient Have a pleasant taste , odor, consistency and color Should set quickly once placed in the mouth Accurate surface detail Manipulation should be easy

10. cont’s Sufficient working time Be economical Have adequate strength while removing from the mouth

11. Impression tray

12. Impression tray impression tray: Is The metallic or plastic carrier ,which are use to take impression of natural teeth & their supporting oral tissues by the impression materials

13. Impression compound Impression compound : is one of the oldest impression materials . It can be described as rigid , reversible impression material which sets by physical change on heat. On a applied heat ,it softens and on cooling it hardens.

14. cont’s it is mainly used for making impressions of edentulous ridges. modeling compound or modeling plastic

15. Impression compound Type I Type II Impression compound Green stick compound

16. Classification Type one-impression compound Type two-tray compound .

17. Indications 1. used for  taking primary impressions of the edentulous ridge p rior to the construction of a custom-made impression tray for complete dentures . 2. Bite registration Giordano, Gen Dent 2000

18. Requirements of ideal impression compound be plastic Biocompatible Harden uniformly when cooled with out distortion Exhibit a smooth glossy surface after flaming Withstand trimming Should not boil

19. manipulation Sticks : Small amount of compound (stick compound) can be softened over a flame . Cakes : Larger amounts of compound are softened in warm water in a thermostatically controlled water path.

20. Conti…………. A thermostatically controlled water path. This water bath maintains a steady softening temperature and is ideal for softening impression compound.

21. Loading the tray: The softening is loaded onto the tray and quickly seated on to the tissue to be recorded. Any delay can cause the impression to harden prematurely.

22. Precautions Prolonged impression in water path causes the compound to become brittle . overheating in water makes the compound sticky and difficult to handle. the impression is removed from the mouth only after it has completely cooled and hardened. Then disinfect the compound.

23. Water bath Alcohol lamp Alcohol torch

24. Advantages of the compound The material can be reused a number of times. accuracy can be improved by flaming the surface. The material has sufficient body to support itself especially peripheral portions .

25. Disadvantages Records less detail because of its high viscosity . compresses soft tissue during impression. Distortion due to its poor dimensional stability Difficult removing if the there are severe undercuts .

26. Zinc oxide- eugenol Impression paste

27. Indications Zinc oxide- eugenol Temporary filling Temporary cementation Root canal filling material For full arch edentulous impression without or minor undercut Bite registration

28. Manipulation

29. Manipulation Equal length of the two paste is extruded Mixed with stainless steel spatula in paper pad or glass slab Mixing time 45-60 s Working time 3-5 min

30. Non- Eugenol Pastes NON-EUGENOL PASTE: developed to overcome the burning sensation caused by eugenol . Used in eugenol irritant patients

31. Elastomeric Impression Materials A material that is used when an extremely accurate impression is essential. The term elastomeric means having elastic or rubberlike qualities.

32. Elastic Aqueous Hydrocolloids Agar Alginate Non aqueous Polysulfide Silicones polyether

33. Polysulfide Silicones polyether

34. Hydrocolloids Reversible and Irreversible Hydrocolloid impression materials Hydro means water. Colloid means gelatin substance. Material used to obtain preliminary and final impressions.

35. Irreversible Hydrocolloid Material that cannot return to a solution state after it becomes a gel. Alginate : is the irreversible hydrocolloid most widely used for preliminary impressions.

36. Alginate

37. Non-aqueous elastomers

38. Non-aqueous elastomers They are soft and rubber like and far more stronger and stable than the hydrocolloids. They are liquid polymers which can be converted to solid rubber at room temperature . These materials are most accurate and dimensionally stable impression materials available in dentistry.

39. Types Polysulfide Condensation polymerizing silicons Addition polymerizing silicons polyether

40. uses In fixed partial dentures Removable partial dentures Complete dentures For bite registration

41. Supplied as Base and catalyst GENERAL PROPERTIES OF ELASTOMERIC MATERIALS Excellent reproduction of surface details They are generally hydrophobic Coefficient of thermal expansion is high The shelf life is two years

42. How you can Control of gagging? 1) seat the patient in an upright position. 2) rinse cold water or mouthwash before impression is made. 3) The impression tray should not be overfilled with impression material.

43. 4) The posterior portion of the impression tray should be seated first. Then, the anterior portion of the tray should be rotated into position. this permits excess impression material to be displaced in an anterior direction away from the soft plate and airway.

44. Cont’s 5. The patient should be instructed to keep the eyes open during the impression producer. 6. The patient should be directed to breath through the nose . the dentist should encourage slow, deep breaths. 7.use topical /spray anaesthesia to numb the area

45. Gypsum Products for Dental Casts

46. is a naturally occurring, white powdery mineral with the chemical name calcium sulphate dehydrate (CaSQ4·2H2O). Their main uses are for: casts or models Dies investments Gypsum:

47. Conti……. models and dies should be accurate replicas of the patient’s hard and soft tissues. models and dies are prepared using materials which are initially fluid and can be poured into the impression, then harden to form a rigid replica .

48. Requirements of dental cast materials: dimensional accuracy adequate mechanical properties be fluid at the time it is poured be sufficiently strong to resist accidental fracture and abrasion be compatible with all the other materials with which it comes into contact

49. Manipulation and setting characteristics Plaster and stone powders are mixed with water to produce a workable mix. (CaSO4)⋅H2O+3H2O→2CaSO4⋅2H2O Calcium sulphate hemihydrate + water Calcium sulphate dihydrate

50. Considerable quantities of air may be incorporated during mixing and this may lead to porosity within the set material. Air porosity may be reduced either by: vibrating the mix in order to bring air bubbles to the surface

51. For hand mixing u need: clean rubber or plastic bowl spatula

52. Factors which control the setting times of gypsum products can be divided into: 1)controlled by manufacturers: the concentration of nucleating agents in the hemihydrate powder Chemical accelerator 2)controlled by the operator: Temperature W/P ratio mixing time Control of setting time:

53. Advantage and dis-Gypsum: Advantages : Inexpensive easy to use Accuracy dimensional stability Disadvantages : brittle

54. Thank you