Elastomeric impression materials

different types of elastomers. applications. recent advances. methods of manipulation

1. ELASTOMERIC IMPRESSION MATERIALS PRESENTED BY, Dr. ARUNIMA UPENDRAN 1 ST YEAR MDS 1

2. Contents Introduction Definition History Classification Ideal requirements Clinical application Properties Elastomers Recent advances Impression making with elastomers Effects of mishandling References conclusion 2

3. Introduction Impression materials are used to produce the accurate replicas of intraoral tissues. There are a wide variety of impression materials available each with their own properties, advantages and disadvantages. Materials in common use can be classified as elastic or non-elastic according to the ability of the set material to be withdrawn over undercuts. 3

4. Definition (GPT-9) 4

5. History Historically, impression making was accomplished with inelastic materials for both soft and hard tissues. Hydrocolloid was initially introduced to make impressions of hard tissues in place of inelastic materials. After World War II (1950s), a group of synthetic rubbery materials called elastomers Polysulphides and Condensation Silicones) , which are capable of making impressions of both soft and hard tissues are developed. 5

6. 1960s : Polyether impression material developed in Germany 1970s : Addition silicone was introduced as a dental impression material 1988 : Latest addition and light cure elastomers 1990-2000 : New auto devices and delivery systems 6

7. Ideal requisites 7

8. Clinical application 8

9. CLASSIFICATIONS 9

10. 10 Elastomeric impression materials are of four types according to the chemical nature of the material:

11. Classification (ACCORDING iso 4823 Based on consistency) Consistency is measured by pressing 0.5 ml of mixed material between two flat plates applying a force of 1.5N. Consistency is defined by average diameter of the resulting disc of the material. Diameter viscosity 11

12. 12 Type Description Min Max Very high consistency(putty like) 35 1 High consistency (heavy bodied) 35 2 Medium consistency (medium bodied) 31 41 3 Low consistency (light bodied) 36 Consistency of test disc diameter(mm)

13. Classification (according ADA specification no:19) Type Max permanent deformation Max flow in compression Max dimensional change in 24 hrs I 2.5 0.5 -0.5 II 2.5 0.5 -1 III 5.5 2 -0.5 13

14. Properties Workability Dimensional stability Accuracy Rheological properties Elasticity Tear strength Biocompatibility Shelf life 14

15. Working and setting time Impression material 23ºC 37ºC 23ºC 37ºC Polysulfide 6.0 4.3 16.0 12.5 Condensation silicon 3.3 2.5 11.0 8.9 Addition silicon 3.1 1.8 8.9 5.9 Polyether 3.3 2.3 9.0 8.3 15 Mean working time (min) Mean setting time(min)

16. Material %decrease in working time when temp increased (mean) %decrease in setting time when temp increased (mean) Polysulfide 30 23 condensation silicon 16 15.5 Addition silicon 38 31 Polyether 31 8.5 16

17. F actors affecting working and setting time temperature - working & setting time Curing of polyether is less sensitive to temperature modification of base/ accelarator paste thinner - WT, slight ST 17 Viscosity Humidity

18. Elasticity An impression material sustains some deformation as it is removed from the mouth but it must rebound to its pre-removal dimensions. An impression with a sufficiently high elastic limit should not sustain permanent deformation. The elastic properties of these elastomeric impression materials improve with an increase in curing time in the mouth An extra time of 1 or 2 min before removal may be beneficial . 18

19. 19 relative amount of permanent deformation in compression following strain induced during removal increases in the following order

20. Stiffness 20

21. Rheological properties Ideally-should flow freely and wet the tissue as it is being injected to achieve adaptation - then resist flow away from the intended surface areas. This will facilitate spreading of heavy-body material on the impression tray and retain it in the tray. This phenomenon is called shear thinning Polyether – rigid – problem preparation on periodontally weak tooth - # of dies & tearing of impression material at the sulcus 21

22. Dimensional stability Polymerization shrinkage Loss of byproduct Thermal contraction from oral temperature to room temperature Imbibitions Incomplete recovery of deformation( visco elastic nature) Pour within 30 mins – polysulfide & condensation silicon 22

23. Tear strength The amount of force needed to tear a specified test specimen divided by the thickness of the specimen is called the tear strength . The ranking of tear strength from the lowest to highest of the impression materials is as follows 23

24. Biocompatibility Probability of allergic reactions is low Polysulfide has the lowest cell death count Polyether has the highest cell death count ,toxicity and contact dermatitis among the class. The most likely problem is lodgment of impression material in gingival sulcus resulting in severe inflammation , 24

25. Subgingival regions are very thin – material can tear Residual segment of impression material difficult to detect  radio opacity of polysulfide can help Severe gingival inflammation. Examine the gingival sulcus immediately after impression removal and also the impression for any evidence of tearing 25

26. Shelf life polysulfide 2 yrs Condensation silicon stannous octoate oxidizes Orthoethyl silicate is not stable in presence of tin ester Addition silicon 1-2 yrs Poly ether > 2yrs 26 Storage Cool, dry environment Tubes always tightly sealed Container closed

27. Polysulphides 27

28. 28 First synthetic elastomeric impression material Also known as MERCAPTAN or THIOKOL Mode of supply Collapsible tubes One labeled Base paste and Other labeled Accelerator paste Consistencies Light body(syringe or wash) Medium body (regular) Heavy body

29. Composition Base paste Polysulphide prepolymer with terminal and pendanthiol (-SH groups)-80-85% Plasticizer – di-n-butyl phthalate Inert filler- possible chalk or titanium dioxide-16-18% Polymerized and cross linked to form rubber To control viscosity To give ‘body’ control viscosity and modify physical properties Catalyst paste PbO 2 / other alternative oxidizing agent-60-68% Sulphur-0.5% Inert oil- paraffin type/ di -n-butyl phthalate To react with thiol groups- setting Setting reaction To form a paste with PbO 2 and sulphur 29

30. 30 Polysulfide prepolymer Lead dioxide polysulphide water

31. Properties working time – 4-7 mins Setting time – 7-10 mins Colder climate- ST A drop of water accelerates the reaction. Lowest viscosity excellent reproduction of details Dimensional stability - Percent contraction (at 24hrs) – 0.40%-0.45% Shrinkage is due to loss of polymerization byproduct such as water 31

32. Deformation on removal caused by rocking the impression while removal; it should be removed with a single swift pull High tear strength – 2500-7000 gm/cm 2 Biocompatibility – lowest cell death count Moderately hydrophilic Unpleasant odor and taste Can be electroplated with copper sulphate 32

33. a dvantages disadvantages 33

34. 34 Condensation silicon

35. 35 First type of silicone impression material Also known as conventional silicone ’ The setting occurs in room temperature so called as RTV silicones (room temperature vulcanization) Mode of supply Collapsible tubes Base paste Accelerator paste / liquid Putty is supplied in jars low, medium, high, and very high (putty) consistencies

36. Composition Composition Function Paste α - ω hydroxyl- terminated polydimethyl siloxane (liquid silicon prepolymer) Inert filler - silica Undergoes cross linking to form rubber Gives ‘body’, controls viscosity & modifies physical properties Liquid Alkyl silica – tetra ethyl silicate Tin compound – dibutyl tin dilaurate / tin octoate Cross linking agent Reaction catalyst 36

37. dimethyl 37 Dimethyl siloxane Tetra ethyl orthosilicate Silicon rubber Ethyl alcohol Stannous octate

38. Properties Working time- 2.5 – 4 mins Setting time – 6-8 mins Tear strength – 2300-2600 N/m % contraction at 24 hrs- 0.38-0.60% Polymerization and evaporation of the alcohol Hydrophobic Can be electroplated with silver and copper Stiffer and harder than polysulfide 38

39. advantage disadvantages 39

40. Addition silicone 40

41. Also known as polyvinyl siloxane or vinyl polysiloxane Mode of supply Collapsible tubes Base paste and Accelerator paste Putty is supplied in jars Consistencies Light body (syringe or wash) Medium body (regular) Heavy body Putty 41

42. COMPOSITION Composition Function Base paste Poly(methyl hydrogen siloxane) Other siloxane prepolymers Fillers- colloidal silica 35-75% Undergoes cross linking controls viscosity Accelerator Di vinyl polysiloxane prepolymers Platinum salt (chloroplatinic acid) Palladium Retarders Fillers Cross linking agents catalyst Hydrogen absorber 42

43. 43 Polymethylhydrosiloxane Divinylpolysiloxane Chloroplatinic acid Silicon rubber

44. Properties Working time – 2-4 mins Setting time – 4-6.5 mins Tear strength – 1500-4300 N/m Percent contraction- 0.14-0.17% Pseudo plastic Exhibits lowest permanent distortion 44

45. Complications with latex gloves Sulphur contamination- inhibits setting Vinyl gloves also – sulphur containing stabilizer used in the manufacturing process Even touching the tooth with the gloves before seating impression – inhibits setting Inhibition of polymerization reaction- distortion Contact of internal surface of impression with gloved hands :- - Failure of the material adjacent to the tray to polymerize - Separation of the tray from the impression material 45

46. OTHER PRECAUTIONS 46 Aluminum sulfate and ferric sulfate → gingival retraction cord → retardation Residues from acrylics, methacrylates and petroleum jelly lubricants may interfere with setting reaction of material

47. Danuta Nowakowska , et al conducted a study on Polymerization time compatibility index of polyvinyl siloxane impression materials with conventional and experimental gingival margin displacement agents They concluded that all of the evaluated displacement agents at laboratory and intraoral temperatures induced changes in the polymerization time of PVS. Therefore, chemical displacement agents should not come into direct contact with PVS impression materials . 47 (J Prosthet Dent 2014;112:168-175)

48. advantages disadvantages Highly accurate High dimensional stability Pleasant to use Short setting time Auto mix available If hydrophilic, good compatibility with gypsum Hydrophobic Expensive Hydrogen gas evaluation in some materials Hydrophilic formulations imbibe moisture Sulfur contamination by latex glove 48

49. Polyether 49

50. First elastomer to be developed primarily to function as an impression material Mode of supply Collapsible tubes Base paste Accelerator paste Third tube containing thinner may be supplied Consistencies Light bodied(syringe or wash) Medium bodied (regular) Heavy bodied 50

51. 51 Base paste (large tube) Imine -terminated prepolymer Inert filler- silica Plasticizer- phthalate Cross linked to form rubber To give body’ control viscosity and physical properties To aid mixing Catalyst paste (small tube) Ester derivative of aromatic sulphonic acid Inert filler – silica Plasticizer- phthalate Initiate cross linking To form paste composition

52. 52 polyethe r Sulfonic ester Cross linked rubber

53. Properties Working time – 3 mins Setting time – 6 mins Tear strength – 1800- 4800 N/m Percent contraction – 0.19 – 0.24% least amount of distortion Pseudo plastic Biocompatibility – contact dermatitis 53

54. advantages disadvantages Dimensional stability Accuracy Shorter setting time Automix available Set material very stiff Imbibition Short working time. Allergic hypersensitivity in some cases . 54

55. 55

56. 56 Recent advances

57. Visible light cured polyether urethane dimethacrylate In early 1988, a visible light cured impression was introduced(Genesis L.D. caulk). Two viscosities - Light and heavy bodied Composition :- Polyether urethane dimethacrylate Photoinitiators ( camphoroquinone ) Photoaccelerators (Diethyl amino ethyl methacrylate ) Silicone dioxide (Filler) 57

58. Properties :- Long working time and short setting time Blue light is used for curing with transparent impression trays Tear strength-6000-7500 gm/cm 2 (Highest among elastomers ) Dimensional stability, flow, detail reproduction, permanent deformation, wettability , compatibility with cast and die materials and electroforming is similar to addition silicone 58

59. Manipulation :- Light body is syringed into the sulcus and over the preparation Heavy body is loaded onto a clear tray and seated over the light body Both are simultaneously cured with a visible light curing unit having an 8mm or larger diameter probe Curing time is approximately 3 m ins 59

60. advantages disadvantages Controlled working time Excellent properties Ease of cold disinfection without loss of quality. The impression material is also compatible with gypsum and silver or copper metallizing baths Need special transparent trays Difficult to cure in remote area 60

61. Hydrophilized vinyl polysiloxane Surfactants are added to reduce the contact angle; dilute solution of soap Most commonly used – non-ionic surfactants Oligoether or polyether substructure Hydrophilic part silicon compatible hydrophobic part 61

62. Diffusion – controlled transfer of surfactant molecules from PVS to aqueous phase Reduction in surface tension Greater wettability 62

63. Bite Registration silicon used for making intraoral or extraoral occlusal bite registrations for fixed or removable restoration and implants. Fast intraoral set time of 20 secs – 1 min Doesnot slump or drip Supplied as cartridges to be used With a caulking gun Commercial name; Exabyte – Gc Jet bite – Coltene whaledent 63

64. Automatic dispensing and mixing devices This latest technique consists of a double barrel caulking gun with mixing tip. The tip contains spirals on the inside. Forcing of the base & accelerator results in its mixing. e.g. Volume mixer (Kerr), Pentamix (3M ESPE) 64 Advantages :- More uniform mix Less air bubbles Reduced working time

65. Senn (GC America) Hybrid polyether / polysiloxane material that has both hydrophilicity and dimensional accuracy, before,during and after set . 65

66. FIT CHECKING SILICONES Specialised addition silicone Used for checking errors in the internal surface of crowns and fpd Available as two paste system Areas of premature contacts are revealed as bare areas, which are marked and removed Commercial name Fit Checker - GC 66

67. Making impression with Elastomers Preparing a tray Managing tissue Preparing the material Making an impression Removing the impression Preparing stone casts and dies 67

68. Impression trays 68

69. Tray adhesives 1.Paint on adhesives  Eg Coltene , Kerr Universal VPS. 2. Spray adhesives Eg   Sili  spray 69

70. Polysulfide Butyl rubber Styrene / acrylonitrile Dissolved in volatile solvent such as chloroform or ketone Silicones Polydimethyl siloxane / similar reactant like silicon & ethyl silicate Hydrated silica forms of ethyl silicate – bonds with the tray Chemical bond between tray material and Polydimethyl siloxane. 70

71. A. Peregrina et al, conducted a study on the effect of different adhesives on vinyl polysiloxane bond strength to two tray materials . Conclusion : The use of GC paint-on universal adhesive provided significantly higher adhesive values than those obtained with the adhesives supplied by the manufacturers of the impression materials tested, with the exception of the Kerr impression and adhesive material combination where no significant differences were found 71 (J Prosthet Dent 2005;94:209-13.)

72. Tissue management Gingival retraction cord double-cord technique is used when the margin is very close to the gingival attachment. Retraction cords - impregnated with a hemostatic agent (epinephrine) An electrosurgical unit Or a soft tissue laser 72

73. Manipulation Hand mixing Static mixing Dynamic mechanical mixing 73

74. Hand mixing 74

75. Static mixing 75

76. Dynamic mechanical mixing 76

77. Making an impression Multiple mix technique Mono phase technique Putty wash technique 77

78. Multiple mix technique 78

79. Monophase technique 79 Only one mix is made- Part of it is placed in the tray Another portion is placed in syringe for injection Medium viscosity of addition and polyether can be used.

80. Putty wash technique 80

81. Giuseppe Varvara et al, conducted an invitro study on Evaluation of defects in surface detail for monophase , 2-phase, and 3-phase impression techniques They concluded that the 3-phase, 2-step impression injection technique provides improved defect-free reproduction of detail, showing fewer defects than other impression techniques. (J Prosthet Dent 2015;113:108-113) 81

82. Removal of impression All elastomeric impression materials are viscoelastic , and it is necessary to use a quick snap to minimize plastic deformation 82

83. Preparation of stone cast and die Debubblizers , a dilute solution of soap - wettability of the silicone impression material for the stone slurry Excellent dimensional stability of addition silicone and polyether impression - construct two or three casts or dies 83

84. Disinfection methods 84

85. Young S. Kang , et al conducted a study on Effects of chlorine-based and quaternary ammonium-based disinfectants on the wettability of a polyvinyl siloxane impression material They concluded that 1. A QAB disinfectant product is more effective at removing surfactant than a CLB disinfectant product. Therefore, a CLB disinfectant provides more time and control. 2. A wetting agent can reverse the hydrophobicity of a disinfected PVS impression material if the duration of cold disinfection is less than 6 hours. 85 (J Prosthet Dent 2017;117:266-270)

86. 86 Property Polysulphides Condensation silicones Addition silicones Polyethers Viscosity 3 viscosities (no putty) 4 viscosities including putty 4 viscosities including putty single viscosity(regular) + diluent + putty Tear resistance Adequate Adequate Adequate Adequate Elasticity Visco elastic material Very good Very good Adequate Accuracy Good with special trays Acceptable with stock trays Good with stock trays Good with special trays Dimensional stability Adequate Poured as quickly as possible Very good Very good in low humidity Comparison of properties of elastomers

87. Effects of mishandling Rough / uneven surface Premature removal Improper mixing ratio Too rapid polymerisation Excessive high accelerator / base ratio – condensation silicon 87

88. 2. Bubbles Too rapid polymerisation preventing flow Air incorporation 88

89. 3.Irregularly shaped voids Moisture / debris 89

90. 4.Rough / chalky stone cast Inadequate cleaning Excess water left on surface Excess wetting agent Premature removal Improper manipulation Failure to delay pour 90

91. 5.Distortion Resin tray not aged sufficiently Lack of adhesion Lack of mechanical retention Premature development of elastic properties Excessive bulk Insufficient relief Continued pressure Movement of tray Premature/improper removal from mouth Delayed pouring 91

92. 6. Faulty electroplating Dimensional change in the elastomer – continued polymerisation during electroplating Electrodeposited metal tend to contract during deposition Flat surface tend to become curved and sharp angles rounded Improper adherence of the electroformed metal to impression material – greater distortion 92

93. References Philips science of dental materials 12 th edition Craig’s restorative dental materials 13 th edition Mc Cabe and walls’ applied dental materials 9 th edition William J O'Brien Dental materials selection 3 rd edition Effects of chlorine-based and quaternary ammonium-based disinfectants on the wettability of a polyvinyl siloxane impression material (J Prosthet Dent 2017;117:266-270) Evaluation of defects in surface detail for monophase , 2-phase, and 3-phase impression techniques (J Prosthet Dent 2015;113:108-113) The dimensional stability of a vinyl polyether silicone impression material over a prolonged storage period (J Prosthet Dent 2013;109:172-178) 93

94. Summary Elastomers since their introduction have revolutionised the art of impression making hence allowing the operator to provide acuurate fitting restorations Addition silicones and polyethers account for major portion of the current practice. Condensation silicones, Polysulfides – more sensitive with respect to handling considerations , mix-and-pour techniques, which may affect accuracy. 94

95. Conclusion The understanding of basic knowledge of the impression materials and their behavior during handling are important for their use in the oral environment and clinical success. The selection of the material best suited for a particular clinical situation and technique rests with the operator. 95

96. 96 Thank you