RIGID IMPRESSION MATERIALS in prosthodontics

RIGID IMPRESSION MATERIALS in prosthodontics

1. INELASTIC IMPRESSION MATERIALS Preceptor: DR.MANOJ kumar PRESENTER: DR. NUPUR CHAUDHARY DATE: 30 TH DECEMBER, 2022 Department of Prosthodontics and Crown & Bridge 1

2. CONTENT • DEFINITIONS • REQUIREMENTS OF AN IMPRESSION MATERIAL • GENERAL PROPERTIES OF IMPRESSION MATERIAL •CLASSIFICATION • IMPRESSION COMPOUND • ZINC OXIDE EUGENOL • MODIFICATIONS OF ZINC OXIDE EUGENOL • IMPRESSION PLASTER • IMPRESSION WAXES • REVIEW OF LITERATURE • CONCLUSION • REFERENCE CONTENTS 2

3. Impression a negative likeness or copy in reverse of the surface of an object; an imprint of the teeth and adjacent structures for use in dentistry; altered cast partial denture impression, coping impression, dental impression, direct bone impression, impression area, impression material, impression tray, master impression, partial denture impression, pick-up impression, preliminary impression, sectional impression, tube impression. (GPT-9) 3

4. Impression materials Any substance or combination of substances used for making a negative reproduction or impression . (GPT-9) Impression materials are used to register and reproduce the forms and relationships of teeth and associated oral tissues. 4

5. Requirements Of An Impression Material Be fluid enough to adapt to oral tissues Be viscous enough to be contained in the tray that is seated in the mouth. • While in mouth they should transform into rubbery or rigid solid in reasonable amount of time. • Set impression should not distort or tear when removed from mouth 5

6. • Impressions made from these materials should remain dimensionally stable at least until cast can be poured . • impression should maintain dimensional stability after removal of cast so that second or third cast can be made from same impression. • materials should be biocompatible. • materials, associated processing equipment, and processing time should be cost-effective 6

7. GENERAL PROPERTIES OF IMPRESSION material 7

8. Biocompatibility And Chemical Properties Non poisonous, non irritant, non allergic to oral tissues Chemically inert Compatible with die or cast material and pattern waxes Acceptable taste and odour for patient 8

9. Rheological properties Low viscosity while inserting for finer details Viscosity should increase quickly to avoid distortion. Pseudoplastic nature — increase flow by stressing for better details. Eg : monophase additional silicones. Suitable mixing and working times by controlling the rate of chemical reaction. 9

10. Characteristic nature of material to become more fluid when applied force is increased; this behaviour involves shear thinning and is strain rate-dependent. Eg - ketchup Property of certain gel or other materials to become liquefied when shaken, stirred, patted or vibrated. Eg - Dental prophylaxis pastes, POP, resin cements P SEUDOPLASTIC THIXOTROPIC 10

11. Shear stress versus shear strain rate for fluids exhibiting different types of rheologic behavior 11

12. Mechanical properties High elasticity and complete elastic recovery. Addition polyvinyl silicones-99.93% Adequate compressive strength to avoid dimensional changes. High tear strength to withstand tearing or shearing stresses during impression removal. Least- Hydrocolloids- 750gm/cm to 800 gm/cm Highest- elastomers- 2000gm/cm to 4000gm/cm High flexibility or strain in compression is needed to permit withdrawal 12

13. YOUNG’S MODULUS OR MODULUS OF ELASTICITY 13

14. Thermal properties Low softening temperature (45-55°C) and sets by 37°C. Very low or zero coefficient of thermal expansion to minimize contraction. Very High Coefficient — Large Contraction • High thermal conductivity to soften or harden or set the impression simultaneously. • Properties should not change while kneading at high temperature 14

15. Aesthetic Properties Good colour contrast to identify margins. Fairly good colour stability Two paste systems have one paste colour to check uniform mixing. Elastomers have different colour so that they can be identified for consistencies 15

16. CLASSIFICATION 16

17. IMPRESSION COMPOUND IMPRESSION WAXES ZINC OXIDE EUGENOL IMPRESSION PLASTER 17

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19. INELASTIC IMPRESSION MATERIALS Exhibit an insignificant amount of elastic deformation when subjected to bending or tensile stresses. Tend to fracture without exhibiting any plastic deformation if the stress from applied pressure exceeds their tensile, shear, or compressive strength values. 19

20. Impression compound ADA SPECIFICATION NO. 3 20

21. IMPRESSION COMPOUND Impression compound, also called modeling plastic , is supplied in the form of sheets and sticks. Available in different colours such as brown, grey, green, red, black and white and is dispensed in many forms such as sheets, cakes, cones, sticks etc. Synonyms : Dental Compound Model Compound Modelling Compound Impression Compound 21

22. CLASSIFICATION 22

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24. MANIPULATION 24

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26. INGREDIENT PARTS RESIN 30 COPAL RESIN 30 CARNUBA WAX 10 STEARIC ACID 5 TALC 25 COLORING AGENT (e.g. ROUGE) 26

27. Plasticizers – Shellac, stearic acid & gutta-percha Fillers, Waxes & resins (non-crystalline) cause high flow & low strength so fillers added. E.g talc, diatomaceous earth, soap stone & french chalk. Coloring agent - Appropriate amount 27

28. APPLICATIONS Primary indication - making an impression of the edentulous ridge More viscous compound, called tray compound, can be used to form a tray for construction of dentures. An impression of soft tissue is obtained with tray compound. This impression is referred to as primary impression . It is then used as a tray to support a thin layer of a second impression material, which is to be placed against tissues. This impression is known as the secondary impression. 28

29. Impression compound cones for securing rubber dam retainers Sticks or small cones of compound are used for securing rubber dam retainer or for recording occlusal relationships The softened compound can be placed directly around the rubber dam retainer or on the occlusal registration plate, but care must be taken that its not too hot 29

30. PROPERTIES OF IMPRESSION COMPOUND 30

31. FUSION TEMPERATURE WHEN IMPRESSION COMPOUND IS HEATED IN HOT WATER BATH MATERIAL STARTS TO SOFTEN AT APPROXIMATELY 39℃ THIS TEMPERATURE AT WHICH MATERIAL LOOSES ITS HARDNESS OR BRTILLENESS ON HEATING OR FORMS A RIGID MASS UPON COOLING IS REFERRED AS FUSION TEMPERATURE . IMPREESION COMPOUND EXHIBITS A FUSION TEMPERATURE RANGE THAN A FIXED POINT. 31

32. Glass transition temperature- 39 ℃ Temperature at which there is an abrupt increase in the thermal expansion coefficient, indicating increased molecular mobility, is called the glass transition temperature ( Tg ) and it is characteristic of the particular glassy structure. 32

33. DIMENSIONAL STABILITY RELAXATION OF IMPRESSION COMPOUND CAN OCCUR IN SHORT PERIOD ESPECIALLY WITH INCREASE IN TEMPERATURE. RESULT IS WARPAGE OR DISTORTION OF IMPRESSION. SAFEST METHOD OF MINIMIZING SUCH DISTORTION IS TO ALLOW THOROUGH COOLING OF IMPRESSION BEFORE REMOVAL FROM MOUTH CONSTRUCT CAST OR DIE AS SOON AS POSSIBLE AFTER IMPRESSION HAS BEEN OBTAINED-AT LEAST WITHIN THE FIRST HOUR 33

34. For type I, flow must be less than 6% at 37°C and more than 85% at 45°C. For type II, flow should be less than 2% at 37°C and between 70% and 85% at 45°C Application of pressure against oral tissue is mandatory for the material to capture the details; hence, this material is called mucocompressive material . An overextended impression can be obtained using this material 34

35. USES Edentulous arch impressions : Since material is thermodynamic, it is possible to make corrections and additions Type II tray compound is applied by trimming and removing the compound material from the stock trays In partially dentulous patients having deep palates , impression compound is added to palate area to customize the stock traY In fixed prosthodontics, impression compound is used to check undercuts in tooth preparations. It is also used in copper band impressions. Impression compound is also used to stabilize the rubber dam during restorative procedures 35

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38. 38 Prolonged immersion in a water bath causes the compound to become brittle and grainy because some of the ingredients may be leached out. Overheating in water makes compound sticky and difficult to handle. Avoid incorporating water while kneading. PRECAUTIONS

39. Effect of wet kneading When the compound is softened in a water bath, kneading material with fingers is customary to improve handling qualities wet kneading increases the flow of both the softened compound and the hardened impression, this increased flow is believed to be caused by water, which acts as a plasticizer, in the compound. • By kneading for 1 to 3 minutes , flow of compound may be more than doubled 39

40. FAILURES Failure to attain a complete hardening of material before withdrawing impression can result in serious distortion of impression by relaxation. • Compound may be softened over flame or by immersion in a warm water bath when large amount is needed. • When a direct flame is used, compound should not be allowed to boil or ignite so that constituents are volatilized. • Prolonged immersion or overheating in water bath is not indicated; compound may become brittle and grainy if some of low molecular weight ingredients leach out of material. • Softening of compound in a warm water bath is method recommended for separating cast from a compound impression after stone sets. 40

41. DISINFECTION RECOMMENDED DISINFECTANT SOLUTION FOR COMPOUND IS 2% ALAKINE GLUTARALDEHYDE SOLUTION. IMPRESSIONS SHOULD BE IMMERSED IN THIS SOLUTION FOR THE REQUIRED AMOUNT OF TIME, RINSED AND POURED IMMEDIATELY . Phillips science of dental materials. Kenneth J Anusavice , W.B Saunders company. First south asia edition, (203-239) 41

42. ZINC OXIDE EUGENOL ADA SPECIFICATION NO. 16 42

43. ZINC OXIDE EUGENOl 1 Cementing and insulating medium. 2. Temporary filling material. 3. Root canal filling material 4. Surgical pack in periodontal surgical procedures. 5. Bite registration paste. 6. Temporary relining material for dentures. 7. Impressions for edentulous patients 43

44. Composition of a Zinc Oxide–Eugenol Impression Paste COMPONENTS PERCENTAGE TUBE NO. 1 (BASE) Zinc oxide (French-processed or U.S.P.) 87 Fixed vegetable or mineral oil 13 TUBE NO.2 (ACCELERATOR) Oil of cloves or eugenol Gum or polymerized rosin 12 50 Filler (silica type) Lanolin 20 3 Resinous balsam Accelerator solution (CaCl2) and color 10 5 44

45. ZOE impression pastes are dispensed as two separate pastes Vegetable or mineral oil acts as a plasticizer and aids in offsetting the action of eugenol as an irritant Oil of cloves, contains 70% to 85% eugenol, is sometimes used in preference to eugenol as it produces less burning sensation for patients when it contacts soft tissues Addition of rosin to paste in second tube facilitates speed of reaction and yields a smoother, more homogeneous product. Canada balsam and Peru balsam are often used to increase flow and improve mixing properties. If mixed paste is too thin or lacks body before it sets, a filler (such as a wax) or an inert powder (such as kaolin, talc, or diatomaceous earth) may be added to one or both of original pastes. 45

46. MANIPULATION 46

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48. SETTING REACTION Setting reaction is a typical acid- base reaction to form a chelate. This reaction is also known as chelation and the product is called zinc eugenolate 48

49. Why should an impression material set quickly in the mouth? Any material which takes a long time to set in the mouth Would obviously be uncomfortable to the patient.  Movement is bound to occur, resulting in stresses and errors in the impression.  Result in a wastage of time for the dentist. In a busy practice, this is unacceptable. Initial setting time is period from beginning of mixing until material ceases to pull away or string out when its surface is touched with a metal rod of specified dimensions. The impressions should be seated in the mouth before the initial set. final set occurs when a needle of specified dimension fails to penetrate surface of the specimen more than 0.2 mm under a load of 50 g 49

50. TIME INTIAL SETTING TIME FINAL SETTING TIME TYPE 1 (HARD WAX) 3-6 MINS 10 MINS TYPE 2 (SOFT WAX) 3-6 MINS 15 MINS 50

51. FACTORS AFFECTING SETTING TIME Particle size of zinc oxide powder smaller the particle size, lesser will be the setting time. By varying the quantity of two pastes. ACCELERATORS : zinc acetate or a drop of water or acetic acid RETARDERS : olive oil and mineral oil Longer the mixing time, shorter the setting time. High temperature and humidity, accelerates setting. Setting can be delayed by cooling glass slab, spatula 51

52. A paste of a thick consistency or high viscosity can compress the tissues, whereas a thin, fluid material results in an impression that captures a negative replica of the tissues in a relaxed condition with little or no compression. In any event, the impression paste should be homogeneous. Pastes of varying consistencies are commercially available. An advantage of a heavier consistency material is its increased strength 52

53. Dimensional StabilitY Dimensional stability of the impression pastes is quite satisfactory. A negligible shrinkage (less than 0.1%) may occur during hardening No significant dimensional change subsequent to hardening should occur with high-quality commercial products. The impressions can be preserved indefinitely without the change in shape that can result from relaxation or other causes of warpage. This condition can be satisfied only if the tray material is dimensionally stable 53

54. ADVANTAGES ENOUGH WORKING TIME TO COMPLETE BORDER MOLDING CHECKED IN MOUTH REPEATEDLY WITHOUT DEFORMING REGISTERS ACCURATE SURFACE DETAILS DIMENSIONALLY STABLE MINOR DEFECTS CAN BE CORRECTED LOCALLY WITHOUT DISCARDING A GOOD IMPRESSION DOES NOT REQUIRE SEPARATING MEDIA AS IT DOES NOT STICK TO CAST DISADVANTAGES REQUIRES A SPECIAL TRAY FOR IMPRESSION MAKING STICKY IN NATURE AND ADHERES TO TISSUES EUGENOL CAN CAUSE BURNING SENSATION AND TISSUE IRRITATION CANNOT BE USED FOR MAKING IMPRESSION OF TEETH AND UNDERCUT AREAS AS IT IS INELASTIC IN NATURE. 54

55. DISINFECTION Recommended disinfectant solution for ZOE impression paste is 2% alkaline glutaraldehyde solution. The impressions should be immersed in this solution for the required amount of time, rinsed, and poured immediately 55

56. MODIFICATIONS OF ZINC OXIDE EUGENOL 56

57. NON-EUGENOL PASTES` One of the chief disadvantages of ZOE pastes is possible stinging or burning sensation caused by eugenol that leaches out and contacts soft tissues. Orthoethoxybenzoic acid , commonly abbreviated as EBA, is a valuable substitute for eugenol in this regard 57

58. SURGICAL PASTES After gingivectomy, zinc oxide– eugenol paste may be placed over the wound to aid in the retention of a medicament and to promote healing. Mixture should be capable of being packed into gingival wounds and interproximal spaces to provide retention of dressing. The final product should be strong enough to resist displacement during mastication, but not so brittle that it shears readily under localized stresses 58

59. BITE REGISTRATION PASTES Used as recording materials in construction of complete dentures and fixed or removable partial dentures. ZOE impression paste offers almost no resistance to closing of the mandible, thus allowing a more accurate interocclusal relationship record to be formed. Furthermore, the ZOE interocclusal record is more stable than one made in wax. 59

60. Classification of gypsum product 60

61. IMPRESSION PLASTER ADA SPECIFICATION NO. 25 61

62. Impression Plaster These impression materials are composed of plaster of Paris, to which modifiers have been added to regulate the setting time and the setting expansion. Impression plaster is rarely used anymore for dental impressions, because it has been replaced by less rigid materials, such as the hydrocolloids and elastomers. Plaster is primarily restricted to use as a final impression (wash impression) in the construction of full dentures 62

63. MANIPULATION • W/P ratio- 0.45 to 0.75 • Freshly mixed plaster is too fluid to be used in a stock impression tray and is normally used in a special tray, constructed using a 1- 1.5 mm spacer. • Another technique is to record the plaster impression as a wash in preliminary compound impression • Compound is deliberately moved during setting to create space for the plaster wash 63

64. Impression plaster is a ß- calcium sulphate hemihydrate Its fluidity makes it suitable for making impressions of soft tissues in the uncompressed state, a characteristic of mucostatic impression material Currently, it is more useful as a bite registration material Impression plaster may be flavoured to make it more acceptable by the patien t 64

65. Soluble plaster Impression plaster sometimes contain potato starch to make it soluble, After the cast hardens, the impression and cast are put in hot water. The starch swells and the impression disintegrates, making it easy to separate the cast. This type is often called “SOLUBLE PLASTEr ” 65

66. Composition Dental plaster K2SO4 Borax Colouring and flavouring agent 66

67. Properties Mixing time- 1 minute Working time- 3 minutes Setting time- 4 – 5 minutes Setting expansion- 2 hour setting expansion Max- 0.15% Increase in W:P leads to decrease in setting expansion. Addition of borax, potassium sulphate and sodium chloride reduces the setting expansion . Strength- 4-5 MPa 67

68. Impression plaster as bite registration material Materials become rigid when used to record bite relationships and anatomical features. These materials can be used to capture relationships providing material do not flow into undercuts, such as below the height of contour of the teeth being recorded. Type 1 gypsum material, also called as impression plaster, in form of interocclusal wafers can be used to record relationships of crown and pontics for soldering and for recording relationships between the arches 68

69. IMPRESSION WAXES ADA SPECIFICATION NO. 4 69

70. Classification of waxes 70

71. IMPRESSION WAXES Used to record zero- undercut edentulous portions of the mouth and are generally used in combination with other impression materials such as polysulfides, ZnO -E impression paste or dental impression compound 71

72. Impression waxes also referred to as bite waxes or corrective waxes. These waxes distort if they are withdrawn from undercut areas. Therefore they are limited to use in edentulous portions of the mouth or in occlusal surface areas. 72

73. Corrective impression waxes Used as a wax veneer over an original impression to contact and register the details of the soft tissues It consists of paraffin, ceresin, beeswax and may contain metal particle The flow at 37 ℃ is 100% Because of this, they get distorted while removing from mouth. 73

74. Uses Functional impressions in case of partial dentures To record posterior palatal seal in dentures Functional impression for obturators (for cleft palate patients) 74

75. Bite registration waxes Waxes are used to record occlusal relationship of opposite quadrants It consists of beeswax, paraffin wax and ceresin wax, certain bite registration waxes contain aluminium or copper particles Its flow at 37℃ ranges from 2.5 to 22% Supplied as U shaped thin sheets, which are sometimes metallized or foil laminated 75

76. REVIEW OF LITERATURE 76

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78. Dr. Venkat Raghu, Dr. Kondumahanti VN Avinash , Dr. Ajna Alex, Dr. Kondumahanti Venkata Sai Prasanth, Dr. Subash Munireddy . Modified technique for the management of the difficulties in recording denture bearing areas with flabby tissues: A technique presentation. Int J Appl Dent Sci 2018;4(4):289-291. 78

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80. Advantages of addition silicone impression material Its shorter setting time, easy to mix, adequate tear strength, extremely high accuracy, absence of any distortion on removal and good dimensional stability suggests that addition silicone can potentially replace impression plaster in conventional technique 80

81. CONCLUSION With time, various advancements are taking place in field of impression materials, older materials like impression plaster, impression compounds and waxes are slowly loosing their place due to their incompetence with newer materials. Still impression compound is treated as the first choice of material for making primary impression of edentulous arches for beginner and mass practices. 81

82. REFERENCES • Phillips’ science of dental materials / [edited by] Kenneth J. Anusavice ; selected artwork by José dos Santos Jr. — 11th ed. Craig RG, Powers JM. Restorative dental materials. 11th ed. New Delhi: Mosby Inc; 2001. Mahalaxmi S.Materials used in dentistry. Gurgaon: Wolters Kluwer Health ;2013. Dr. Venkat Raghu, Dr. Kondumahanti VN Avinash , Dr. Ajna Alex, Dr. Kondumahanti Venkata Sai Prasanth, Dr. Subash Munireddy . Modified technique for the management of the difficulties in recording denture bearing areas with flabby tissues: A technique presentation. Int J Appl Dent Sci 2018;4(4):289-291 82

83. THANK YOU 83