Elastomers

DR. PRAJAKTA GIR

1. PRESENTED BY : Dr. PRAJAKTA BALI GIR MDS 1 st YEAR ELASTOMERS

2. INTRODUCTION HISTORY CLASSIFICATION OF IMPRESSION MATERIAL ELASTOMERIC IMPRESSION MATERIALS POLYSULPHIDES POLYSILICONES : CONDENSATION POLYSILICONES ADDITION POLYSILICONES POLYETHERS PROPERTIES CONTENTS DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

3. MANIPULATION OF ELASTOMERIC MATERIALS MIXING SYSTEMS IMPRESSION TECHNIQUES FAILURE CAUSES DISINFECTION REVIEW OF LITERATURE CONCLUSION REFERENCES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

4. INTRODUCTION

5. INTRODUCTION 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 (GPT 9) IMPRESSION MATERIAL - Any substance or combination of substances used for making an impression or negative reproduction. (GPT 9) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

6. HISTORY YEAR / DECADE EXTENT 1730s Sealing wax and plaster casts were introduced 1820 Impression tray was made 1844 Plaster impressions were developed 1857 Modeling compound was developed 1883 E.C.C. Stanford, a British pharmacist, discovered algin, the precursor for alginate 1925 Reversible hydrocolloid introduced by Alphons Poller , an Austrian who patented it as “ Nogacoll ” DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

7. YEAR / DECADE EXTENT 1929 Commercial production of alginate by a company named “ Kelco ” in California 1931 Hydrocolloid “ Denticole ” was first marketed 1935 A.W. Sears promoted the use of agar as an impression material for fixed partial dentures 1953 Polysulfide impression material was introduced 1960s Polyether impression material was introduced 1970s Condensation silicone was introduced 1980s Addition silicone material was introduced DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

8. CLASSIFICATION OF IMPRESSION MATERIALS

9. 9 IMPRESSION MATERIALS NON ELASTIC ELASTIC PLASTER ZOE IMPRESSION COMPOUND HYDROCOLLOIDS NON-AQUEOUS AGAR ALGINATE POLYSULPHIDES SILICONES POLYETHERS William J O'Brien Dental materials selection 3rd edition DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

10. 10 IMPRESSION MATERIALS SETTING MECHANISM DISPENSING MECHANISM CLINICAL APPLICATIONS PRESSURE APPLIED AREA MECHANICAL PROPERTIES TRAY USED V Shama Bhat Science of Dental Materials Clinical Applications Second Edition DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

11. 11 SETTING MECHANISM 1 . REVERSIBLE = impression compound, dental waxes, and agar hydrocolloids 2. IRREVERSIBLE = alginate, zinc oxide eugenol, and elastomers 3. THERMAL CHANGE = Impression compound, agar-agar, impression waxes. 4. CHEMICAL CHANGE = zinc oxide eugenol impression pastes, impression plaster, elastomers, alginates. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

12. 12 DISPENSING MECHANISM 1. POWDER : Impression plaster, alginates 2. TWO PASTES SYSTEM : ZnOE impression pastes, polysulphides and polysilicones 3. THREE PASTES SYSTEM : Chemically activated polyether (base, reactor, thinner ) 4 . SINGLE PASTES SYSTEM : Light activated polyether 5. GELS : Agar-agar 6. SUPPLIED IN THE FORM OF CAKES, CYLINDERS, STICKS, SHEETS AND CONES : impression compound, impression waxes DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

13. 13 CLINICAL APPLICATIONS 1. PRIMARY/PRELIMINARY IMPRESSIONS, e.g. impression compound, impression waxes, alginates, elastomers (heavy and regular bodies) 2. SECONDARY/CORRECTIVE WASH IMPRESSIONS , e.g. impression plaster, ZnOE impression pastes, elastomers, polysulfides, polyethers , poly silicones (light bodies), (agar-agar) 3. BORDER MOULDING IMPRESSION , e.g. green stick compound 4. CAVITY IMPRESSIONS FOR INLAYS AND ONLAYS , e.g. elastomers 5. CROWN AND BRIDGE IMPRESSION , e.g. hydrocolloids-agar-agar, alginates elastomers– polysilicones , polysulphides, polyethers 6. PARTIAL DENTURE IMPRESSIONS , e.g. hydrocolloids-agar-agar, alginates , elastomers– polysilicones , polysulphides, polyethers . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

14. 14 PRESSURE APPLIED MUCOCOMPRESSIVE : Impression compound 2. MUCOSTATIC : Impression plaster DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

15. 15 AREA EDENTULOUS CONDITION : All impression materials (impression compound, impression waxes, impression plaster, ZnOE impression pastes, hydrocolloids, elastomers) 2. DENTULOUS CONDITION : Hydrocolloids and elastomers are only to be used . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

16. 16 MECHANICAL PROPERTIES 1 . ELASTIC IMPRESSION MATERIALS : These when deformed, should recover elastically, e.g. hydrocolloids (agar-agar and alginates) elastomers ( polysilicones , polysulphides and polyethers ) 2. NONELASTIC IMPRESSION MATERIALS : Impression compound, impression waxes, impression plaster, zinc oxide eugenol impression pastes. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

17. 17 TRAY USED A . STOCK TRAYS = 1. Rim lock perforated trays Eg. Alginate, Elastomers 2. water cooled Eg. Agar 3. plastic trays a. perforated- Eg. Alginate, Elastomers b. Non perforated- Eg. Impression compound B. SPECIAL TRAYS = 1 . Base plate wax Eg. ZOE paste, Medium body DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

18. ELASTOMERIC IMPRESSION MATERIALS

19. An elastomer can be defined as a three dimensional polymer network which has good elasticity and has a wide elastic range within an intended working temperature range. Dental elastomers are a group of rubbery polymers , which are either chemically or physically crosslinked. They can be easily stretched and they rapidly recover their original dimensions when the applied stress is released . ABOUT ELASTOMERS DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

20. The viscoelastic property of these materials is easy enough to make an accurate impression in undercut areas with less distortion and dimensional instability . Introduced in the 1950s , impression materials of this group are usually called nonaqueous elastomeric impression materials. The long polymer chains cross-link during curing . The molecular structure of elastomers can be imagined as a 'spaghetti and meatball' structure, with the meatballs signifying cross-links . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

21. The first elastomeric impression materials were polysulfides , followed by condensation silicones , polyethers , and addition silicones . Condensation silicones were made available to dentists in 1955 , polyether in 1965 , and addition silicones in 1975. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

22. CLASSIFICATION OF ELASTOMERIC IMPRESSION MATERIALS

23. 23 ELASTOMERS ADA NO :19 CHEMICAL NATURE VISCOSITY METHOD OF POLYMERIZATION METHOD OF DISPENSING CLINICAL APPLICATIONS OR USES DIMENSIONAL STABILITY, FLOW AND PERMANENT DEFORMATIONS 1 2 3 4 5 6 V Shama Bhat Science of Dental Materials Clinical Applications Second Edition DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

24. POLYSULPHIDES POLYSILICONES - Addition polysilicones - Condensation polysilicones POLYETHERS - Light activated polyethers - Chemically activated polyethers ACCORDING TO CHEMICAL NATURE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

25. 0 = VERY HIGH VISCOSITY MATERIAL - putty like elastomers. 1 = HIGH VISCOSITY MATERIAL - heavy body elastomers. 2 = MEDIUM VISCOSITY MATERIAL - regular body elastomer . 3 = LOW VISCOSITY MATERIAL - light body elastomer-syringe consistency. ACCORDING TO VISCOSITY DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

26. ADDITION POLYMERIZATION MATERIALS, e.g. Polyether, addition polysilicones 2 . CONDENSATION POLYMERIZATION MATERIALS, e.g. condensation polysilicones and polysulphides ACCORDING TO METHOD OF POLYMERISATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

27. SINGLE PASTE SYSTEM: Light activated polyether TWO PASTE SYSTEM (BASE + REACTOR PASTE): polysulphides, addition and condensation polysilicones TWO PASTE SYSTEM HAVING PSEUDOPLASTIC PROPERTY-SUPPLIED IN A SINGLE CONSISTENCY WHICH CAN BE USED AS A TRAY AND SYRINGE MONOPHASE MATERIAL, e.g. addition polysilicones SINGLE PASTE (BASE PASTE) WITH REACTOR LIQUID, e.g. condensation polysilicones THREE PASTE SYSTEM-BASE + REACTOR + BODY MODIFIER (THINNER), e.g. chemically activated polyether ACCORDING TO METHOD OF DISPENSING DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

28. ACCORDING TO CLINICAL APPLICATIONS OR USES KIND OF IMPRESSION OBJECT OF IMPRESSION COMBINATIONS Double mix single impression Cavity impressions for inlays and onlays Light + heavy body Double mix , double impression (reline technique) Cavity impressions for inlays, onlay , etc. impressions of a crown and impressions of a partial denture Putty + light body or putty + regular body Individual tray method (tube impression) Impression for a crown (single tooth) Regular body or light body Single mix single impression impression Cavity impressions for inlays and onlays . Impressions for partial dentures Regular or heavy having pseudoplastic property or light or regular body DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

29. ACCORDING TO DIMENSIONAL STABILITY, FLOW AND PERMANENT DEFORMATIONS TYPES MAXIMUM PERMANENT DEFORMATION % MAXIMUM FLOW IN COMPRESSION % MAXIMUM DIMENTIONAL CHANGE IN 24 HRS % I 2.5 0.5 0.5 II 2.5 0.5 1.0 III 2.5 2.0 0.5 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

30. CHEMISTRY AND COMPOSITION OF ELASTOMERIC IMPRESSION MATERIAL 30

31. POLYSULPHIDES

32. ABOUT POLYSULPHIDES Polysulfide impression material was the first nonaqueous elastomeric “rubber” impression material developed for dentistry. Often, polysulfide materials are called “rubber” or “rubber base” materials, even though polyether and silicone materials are also rubber materials. Due to their high accuracy and relatively low cost , polysulfide rubbers are widely used for fixed partial denture application. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

33. These materials are useful for multiple impressions when extra time is needed. One very important difference between types of elastomeric impression materials is the adhesive that is used to bond the impression material to a nonperforated tray. Each impression material has its own adhesive, which will not work with other types of material . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

34. VULCANISATION AND CHEMICAL REACTION The process of heating the rubber with sulphur to produce cross-linking. The main component of polysulfide materials is mercaptan (-SH) . The lead dioxide catalyzes the condensation of the terminal and pendant -SH with -SH groups on other molecules, resulting in chain lengthening and cross-linking . In the process, the material changes from a paste to a rubber . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

35. The reaction is accelerated by increase in temperature and by the presence of moisture . Lead dioxide is the component that gives polysulfide its characteristic brown colour . Lead dioxide is toxic and has bad smell , so it has been replaced in recent products by peroxide compounds . It is an exothermic reaction with 3°C–4°C rise in temperature . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

36. It is a condensation reaction in which water is formed as a by product . Polysulfide impression materials shrink 0.3% to 0.4% during the first 24 hours , and thus models and dies should be prepared promptly . mercaptan + lead dioxide = polysulfide rubber + lead oxide + water DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

37. DISPENSING These are supplied as a 2 paste system in collapsible tubes, and are available in all 4 viscosities , light, regular, heavy body and putty like consistencies. Note: L → Light body, R → Regular body, H → Heavy body, P → Putty consistency DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

38. ALTERNATIVE NAMES Thiokol corporation material : By the name of the first-manufacturer. Mercaptan impression material : By chemistry (–SH groups). Vulcanising impression material : By processing terminology. Permlastic (Kerr) Omni-Flex (GC America) Coe-Flex DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

39. COMPOSITION BASE PASTE Polysulphide prcpolymer with terminal and pendant thiol (–SH) groups Plasticizer-di-n-butyl phthalate Inert filler – possibly chalk or titanium dioxide REACTOR PASTE PbO2 (lead dioxide) (or, – Cu (OH)2 ) oxidation of ( cumane hydroxide) Sulphur Dibutyl phthalate (plasticizer) Inert oil (oleic acid, stearic acid, Mg stearate) Deodorants DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

40. MANIPULATION The two pastes are dispensed in equal lengths on a paper mixing pad. An impression material spatula is used to mix the two pastes . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

41. The pastes are swirled and stropped together until a homogeneous paste is obtained. The side of the spatula blade is used to scrape unmixed material from the paper pad and then to mix it into the rest of the material. The mixed material is loaded into the tray and placed in the mouth as a viscous paste. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

42. USES To record dentulous impressions for preparation of crowns, bridges, inlays, onlays , partial dentures, etc. To record impressions of edentulous arches in the preparation of complete dentures . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

43. ADVANTAGES It has a longer working time Highest flexibility 14–17%, easy removal over undercuts Highest tear strength (2,500–7,000 gm/cm) Less expensive when compared to other elastomers Long shelf-life. Can be electroplated with silver. It is compatible with dye stones . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

44. DISADVANTAGES Disagreeable odour and taste due to presence of PbO2 Longer setting time Dimensional change due to evaporation of byproducts, i.e. water (3–6%) It will stain clothes Second or multiple dye pouring is less accurate. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

45. POLYSILICONES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

46. ABOUT POLYSILICONES The many disadvantages of polysulfide rubber base impression material resulted in the development of the silicone impression materials . Depending on the type of chemical reaction , there are two types of silicone rubber-based impression materials, namely, condensation silicones and addition silicones , also known as polyvinyl siloxanes . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

47. CONDENSATION POLYSILICONE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

48. CONDENSATION SILICONE Condensation silicone impression materials were the next elastomeric impression material to be developed for dentistry. They are based on silicone rubber, which is commonly used in other industries. It is also called as room temperature vulcanizing (RTV) silicones . Also known as conventional silicones . These materials are not popular at present because newer materials provide better results . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

49. DISPENSING It is supplied in 2 forms , two paste form in collapsible tubes, i.e. base + reactor or The base paste and reactor liquid. Materials are available in all 4 viscosities or consistencies. L → Light body, R → Regular body, H → Heavy body, P → Putty consistency DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

50. COMPOSITION LIQUID Tri or tetra functional ethyl silicate Organometallic compound, tin octoate Reinforcing fillers or thickening agents Colour pigments (organic dyes) BASE Moderately low molecular wt. silicone prepolymer with hydroxyl terminated group Reinforcing fillers: (Copper carbonate, colloidal silica of particle size ranging from 2–10 mm) 35–75% (L, R, H, Putty consistencies) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

51. SETTING REACTION On mixing the two components, base and reactor the reaction begins immediately in which the terminal hydroxyl groups of prepolymer chains react with the cross linking agent, tetra ethyl orthosilicate , under the influence of catalyst, i.e. tin octoate . Each molecule of cross-linking agent can potentially react with four prepolymer chains, causing extensive crosslinking. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

52. Which produces increase in viscosity and rapid development in elastic properties . It is a condensation reaction producing ethyl alcohol as by product. The multifunctional ethyl silicate produces a network or cross linked structures that reduce permanent deformation and flow values . Moderately low molecular. wt. silicone prepolymer with OH terminal group + ethyl silicate → ortho silicate rubber DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

53. MANIPULATION The manipulation of condensation silicones is the same as for polysulfides, except that the silicone material may be supplied as a base paste plus a liquid catalyst. When it is supplied in this form, one drop per inch of extruded base paste is usually recommended. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

54. Electroplating is an option. Because of the high polymerization shrinkage , the cast or die must be poured as soon as possible. Higher temperatures and humidity shorten the setting time. Speedex ( Coltene / Whaledent ), Accoe (GC America) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

55. USES Used for recording dentulous impressions in preparation of crowns, bridges, inlays, onlays and to some extent for partial dentures. Used to record the edentulous impressions in the preparation of complete dentures. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

56. ADVANTAGES It has adequate working time and setting times Clean, pleasant odour and there is no staining Adequate tear strength Better elastic recovery properties on removal Available in complete range of viscosities, thus allowing flexibility in choosing an impression material. Can be electroplated with silver or copper . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

57. DISADVANTAGES Lower flexibility than polysulphides Poor dimensional stability due to release of byproducts, ethyl alcohol Less accuracy if poured immediately, cast pouring is delayed by 20–30 min for maximum elastic recovery. Requires a very dry field. material may be hazardous if not handled properly. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

58. Since condensation silicones are hydrophobic in nature, air bubbles are likely to occur in the impressions, as the material is readily repelled by water or saliva. Poor to adequate shelf life (1–2 years). Slightly more expensive Putty-wash method is technique sensitive Liquid component of the reactor paste material may be hazardous if not handled properly. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

59. ADDITION POLYSILICONE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

60. Addition silicones are the most popular type of elastomeric impression material, especially for crown and bridge impressions. Addition silicone impression materials are also called vinyl polysiloxanes and polyvinylsiloxanes. They are expensive, however, and therefore are not used for routine study casts ADDITION POLYSILICONE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

61. Supplied as two paste systems and available in all four viscosities . Also available in a single consistency called single phase or monophase material. It can be used both as a tray and a syringe material due to pseudoplastic property DISPENSING DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

62. Extra-low Low(syringe or wash) Medium (regular)/monophase High (tray) Putty (extra-high) consistencies AVAILABLE IN DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

63. COMPOSITION BASE Polymethyl hydrogen siloxane or moderately low molecular weight silicone pre-polymer with silane terminal groups Reinforcing fillers: (Powdered silica) REACTOR Polydimethyl vinyl siloxane or moderately low molecular weight silicone prepolymer with vinyl terminal group Reinforcing fillers: (Powdered silica) Chloroplatinic acid (H2PtCl6 ) Low molecular weight liquid polymer ( polydimethyl hydrogen siloxane) Finely divided platinum or palladium Colour pigment (different for L, R, H, P) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

64. On mixing the two pastes, a platinum catalyzed addition reaction occurs causing cross-linking between the two types of siloxane prepolymers to form silicone rubber. The reaction does not have byproducts which results in a minimum dimensional change during polymerization reaction. Side reactions will produce hydrogen gas . SETTING REACTION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

65. The hydrogen gas could also be formed if moisture or residual silane groups are present It could also be due to the decomposition of the catalyst producing hydrogen gas. The present day silicones contain a noble metal such as platinum or palladium to act as scavenger for the hydrogen gas evolved. The hydrogen gas evolved can result in pin hole voids in the impression which might affect the master cast. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

66. Remedy is to pour the impression one hour after recording the impression or elimination of impurities if present or subjecting the impression to vacuum before pouring the stone cast Addition-silicone impressions poured in high-strength stone at 15 minutes. A, Bubbles are caused by the release of hydrogen. B, No bubbles are apparent because palladium hydrogen absorber is included in the impression material . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

67. Addition silicones are as easy to handle as condensation silicones. Because there is the possibility of hydrogen release on setting, finely divided palladium is added to some products to absorb the hydrogen and prevent bubbles from forming on stone die surfaces. If a product does not contain a hydrogen absorber, an hour should pass before pouring dies, and the impression should stand overnight before epoxy dies are poured. MANIPULATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

68. Automatic mixers that provide quick, bubble-free mixes are available with several products. Addition silicones can be electroplated with both copper and silver. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

69. Extrude (Kerr) Express (3M/ESPE) Aquasil (Dentsply Caulk) Genie (Sultan Chemists) Virtual ( Ivoclar Vivadent ) 3 M Tm Express Tm Impression Material system. (3 M) 3 M Tm Express Tm STD Putty. (3 M) 3 M Tm Express Tm Impression Material Refills (3 M) 3 M Tm Imprint Tm Monophase Impression Material system (3 M) 3 m Tm Imprint II Impression Material system (3 M) AVAILABLE AS DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

70. Latex gloves have been shown to adversely affect the setting of addition silicone impressions. Sulfur compounds that are used in the vulcanization of latex rubber gloves can migrate to the surface of stored gloves. These compounds can be transferred onto the prepared teeth and adjacent soft tissues during tooth preparation and when placing tissue retraction cord. SOME INFORMATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

71. They can also be incorporated directly into the impression material when mixing two putties by hand. These compounds can poison the platinum-containing catalyst, which results in retarded or no polymerization in the contaminated area of the impression. Thorough washing of the gloves with detergent and water just before mixing sometimes minimizes this effect, and some brands of gloves interfere with the setting more than others. Vinyl and nitrile gloves do not have such an effect DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

72. Residual monomer in acrylic provisional restorations and resin composite cores has a similar inhibiting effect on the set of addition silicone materials. The preparation and adjacent soft tissues can also be cleaned with 2% chlorhexidine to remove contaminants. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

73. Hydrophilic polyvinyl siloxane These materials have been recently introduced to overcome the high surface tension and incompatibility with the moisture. Hydrophobic nature causes difficulty in pouring the cast. To render the surface hydrophilic, the surfactant is added to the paste . This surfactant reduces the contact angle which increases wettability and simplifies the pouring of gypsum model. MODIFICATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

74. The hydrophobic material have contact angle of approximately 95°, where as that of hydrophilic material have contact angle of 30°-35° and has better wetting . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

75. Vinyl siloxane ether It is combination of PVS and PE impression materials and having combined benefit of both materials No bitter taste of polyether Hydrophilic in nature Good elasticity and elastic recovery It is having high tear strength, excellent dimensional accuracy and resistance to deformation. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

76. It is most widely used for the crown and bridge impressions Cavity impressions of inlays and onlays Impressions for partial and complete dentures. USES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

77. Produce highly accurate impressions Pleasant to handle and no disagreeable taste Excellent elastic recovery–99.93% Shorter setting time Dimensionally more stable as there is no elimination of byproducts Can be electroplated with silver or copper Multiple dye-pour is possible ADVANTAGES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

78. More expensive with automatic mixing devices Shorter working time It may release hydrogen gas on setting and produce pin point voids in the impression if absorbent is not present in the material. Hydrophobic material causes difficulty in obtaining cast/dye, without air bubbles. DISADVANTAGES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

79. POLYETHER DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

80. POLYETHER This material was introduced in Germany is 1960. This was the first elastomer to be developed as an impression material only unlike others, which were adapted from other uses. It was developed in an attempt to combine the good mechanical properties of the polysulfides with the dimensional stability of the silicones . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

81. DISPENSING It is dispensed as 3 pastes system, base, reactor and body modifier (thinner). It is available in 3 viscosities, i.e. light, regular and heavy bodies. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

82. SETTING REACTION When the base paste is mixed with catalyst paste, the cation ring opening addition polymerization occurs, the ionized form of sulphonic acid provides the initial source of cation and in each stage of the reaction involves opening of an aziridine ring and production of a fresh cation. Reaction is addition polymerization reaction without the formation of by-products DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

83. Since each polyether molecules have 2 imine terminal groups, individual propagation reaction may produce simple chain lengthening reaction and cross-linking. As the reaction proceeds, the viscosity increases and eventually relatively rigid cross linked rubber is produced. Base imine terminated polyether + reactor sulphonic acid → polyether rubber DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

84. COMPOSITION BASE Imine terminated polyether of moderately low molecular weight Colloidal silica Glycol ether phthalate REACTOR Ester derivative of aromatic sulphonic acid Colloidal silica Glycol ether phthalate , Octyl phthalate (thinner) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

85. AVAILABLE AS Impression f (ESPE) Impregum Penta (ESPE) Permadyue Garant 2:1 (ESPE) Permadyne Heavy body (ESPE) Permadyne Light Body (ESPE) Permadyue Penta H (ESPE) Permadyne Penta L (ESPE) Impregum F, Permadyne (3M ESPE), Polyjel (Dentsply/Caulk) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

86. MANIPULATION The manipulation of polyethers is similar to that of polysulfides and silicones. Equal lengths of base and catalyst paste are mixed vigorously and rapidly (30 to 45 seconds), because the working time is short. They are easy to mix. The impressions can be readily silverplated to produce accurate dies. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

87. Precautions should be taken to mix the material thoroughly and to avoid contact of the catalyst with the skin or mucosa because tissue reactions have been observed. A handheld gun-type mixer that provides quick, bubble-free mixes is available for Permadyne Garant (3M ESPE). Also, an automatic mixing device ( Pentamix , 3M ESPE) is available for use with a polyether packaged in polybags ( Impregum Penta). DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

88. USES In the preparation of crowns and bridges In cavity preparations for inlays and onlays In construction of partial and complete dentures . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

89. ADVANTAGES Have pseudoplastic properties, that is, same mix can be used as a tray and syringe material. Addition of thinner to the base and reactor pastes increases flow properties. These are dimensionally stable as there are no liberation of byproducts and less polymerization shrinkage. Produce more accurate casts and permits multiple dye pours. Shorter setting time. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

90. Have less hydrophobic, hence better wetting and good casts are obtained. Long shelf-life-no objectional odour and less distortion on removal from mouth. Cast pouring can be delayed for few hours even a week. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

91. DISADVANTAGES Very expensive when compared with other elastomers High stiffness Low tear strength Electroplating is not easy Not available in complete ranges of viscosities Catalyst can be sensitive to the patients . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

92. LIGHT ACTIVATED POLYETHER DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

93. DISPENSING : Available in 2 viscosities, light body supplied in disposable syringes and heavy body, packed in collapsible tubes. LIGHT ACTIVATED POLYETHER (INTRODUCED IN 1988) DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

94. Visible light curing polyether urethane dimethacrylate elastomer resin Visible light cure photoinitiators camphoroquinone and photoaccelerators -dimethyl aminoethyl methacrylate. Silicon dioxide-as fillers (It has refractive index close to that of the resin in order to provide the translucency necessary for depth of cure) COMPOSITION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

95. Excellent elasticity Command setting, infinite working time and short setting times. Very low volume shrinkage on setting The impression can be stored up to two weeks. PROPERTIES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

96. Mixing is not required. Light body material is syringed into cavity preparation. The special transparent tray is loaded with heavy body material and in the patients mouth. MANIPULATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

97. After the tray is seated in the mouth, both materials are cured simultaneously using a visible light curing unit. The curing time is approximately 3 minutes. The light source is tungsten halogen bulb with a filter λ = 460–480 nm . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

98. Command setting, property, i.e. infinite working time and short setting time Excellent mechanical and clinical properties No mixing is required, hence no trapping of air or voids and less wastage. ADVANTAGES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

99. Requires a special tray that is transparent to the visible light, to cure the material . DISADVANTAGES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

100. PROPERTIES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

101. HANDLING PROPERTIES PROPERTIES POLYSULPHIDE CONDENSATION SILICONE ADDITION SILICONE POLYETHER PREPARATION 2 pastes 2 pastes or paste liquid 2 pastes 2 pastes HANDLING simple simple simple simple EASE OF USE fair fair good good DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

102. PROPERTIES POLYSULPHIDE CONDENSATION SILICONE ADDITION SILICONE POLYETHER PATIENT REACTION Unpleasant , stains Pleasant , clean clean Unpleasant , clean EASE OF REMOVAL Easy Moderate Moderate Moderate to difficult SETTING TIME 8–12 6–8 3–7 4.5 WORKING TIME 5–7 3. 2–4.5 2.5 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

103. PROPERTIES POLYSULPHIDE CONDENSATION SILICONE ADDITION SILICONE POLYETHER STABILITY 1 h Immediate pour 1 w 1 w kept dry WETTABILITY AND EASE OF POURING Excellent Fair Fair to good Good DIE MATERIAL stone stone stone stone ELECTROPLATING yes yes yes yes DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

104. PROPERTIES POLYSULPHIDE CONDENSATION SILICONE ADDITION SILICONE POLYETHER DISINFECTION fair excellent excellent fair COST low moderate High to very high high ELASTIC RECOVERY % 94.5 -96.9 98.2 -99.6 99 -99.9 98.3 -99 FLEXIBILITY % 8.5 - 20 3.5 -7.8 1.3 -5.6 1.9 -3.3 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

105. PROPERTIES POLYSULPHIDE CONDENSATION SILICONE ADDITION SILICONE POLYETHER FLOW % 0.4 -1.9 < 0.10 <0.05 <0.05 SHRINKAGE, 24 HOURS % 0.4 – 0.5 0.2 -1.0 0.01 – 0.2 0.2 – 0.3 TEAR STRENGTH g/cm 2240 - 7410 2280 - 4370 1640 - 5260 1700 - 4800 O’Brien Dental Materials & their Selection 4 th edition DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

106. RHEOLOGICAL PROPERTIES : All elastomeric impression materials exhibit shear-thinning characteristics before setting. A pseudoplastic material displays decreasing viscosity with increasing shear stress, and recovers its viscosity immediately upon a decrease in shear stress. ELASTICITY AND VISCOELASTICITY : An impression material sustains some deformation as it is removed from the mouth but it must rebound to its preremoval dimensions. The simplest model that demonstrates the viscoelastic behavior is a Maxwell-Voigt model SOME INFO DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

107. keeping the time of applied force on the impression to a minimum will result in the least amount of permanent deformation. This explains why removal of the impression should be done in a snap, if possible, and a teasing or rocking method should be avoided TEAR STRENGTH : Low-viscosity impression materials are used in interproximal and subgingival areas during impression making. The subgingival regions of the impression are often very thin and can tear during impression removal, leaving a portion embedded within the gingival sulcus SOME INFO DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

108. A tear-strength test measures the resistance of an elastomeric material to fracture when subjected to a tensile force acting perpendicular to a surface flaw. A quick snap in removing the impression usually increases the tear strength, as the action increases the resistance of the material to deformation DIMENSIONAL STABILITY : There are six major sources of dimensional change: (1) polymerization shrinkage, (2) loss of a condensation reaction by-product (water or alcohol) SOME INFO DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

109. ( 3) thermal contraction from oral temperature to room temperature, (4) absorption of water or disinfectant over a period of time, (5) incomplete recovery of deformation because of viscoelastic behavior, and (6) incomplete recovery because of plastic deformation . SOME INFO DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

110. Working time longest to shortest agar > polysulfide > silicones > alginate = polyether Setting time shortest to longest alginate < polyether < agar < silicones < polysulfide COMPARISON OF PROPERTIES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

111. Stiffness most to least polyether > addition silicone > condensation silicone > polysulfide = hydrocolloids Tear strength greatest to least polysulfide > addition silicone > polyether > condensation silicone >> hydrocolloids COMPARISON OF PROPERTIES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

112. Cost lowest to highest alginate < agar = polysulfide <condensation silicone < addition silicone < polyether Dimensional stability best to worst addition silicone > polyether > polysulfide > condensation silicone > hydrocolloid COMPARISON OF PROPERTIES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

113. Wettability best to worst hydrocolloids > polyether > hydrophilic addition silicone > polysulfide > hydrophobic addition silicone = condensation silicone Castability best to worst hydrocolloids > hydrophilic addition silicone > polyether > polysulfide > hydrophobic addition silicone = condensation silicone COMPARISON OF PROPERTIES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

114. MANIPULATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

115. The steps to be followed while manipulating the elastomeric impression materials are: Selection of the materials Preparation of custom/special trays Proportioning and mixing Impression techniques Application of wetting agents (surface tension reducing agents) on the impression (as it is hydrophobic) Pouring of stone dies. MANIPULATION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

116. The selection of the rubber impression material should be based on the clinical usage of the material and the properties required . SELECTION OF MATERIAL DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

117. A special tray with spacer has to be prepared with acrylic resins by using the primary/preliminary cast of the patients mouth. For putty elastomers perforated stock trays or disposable trays can be used. PREPARATION OF CUSTOM/SPECIAL TRAYS DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

118. Elastomers are not adhesive to the trays. Adhesion can be obtained by application of adhesives to the trays. For polysulphides , butyl rubber or styrene dissolved in chloroform or ketone can be used. For polysilicones – polydimethyl siloxane and ethyl silicate can be used to create a physical bond with the impression trays ADHESION TO THE TRAY DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

119. 119

120. Three types of systems are available to mix the catalyst and base thoroughly before taking the impression: Hand mixing Static auto mixing Dynamic mechanical mixing MIXING DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

121. HAND MIXING The user should dispense the same lengths of materials onto a mixing pad or glass slab . The catalyst paste is first collected on a stainless steel spatula and then spread over the base paste. The mixture is then spread over the mixing pad. The mass is then scraped up with the spatula blade and spread uniformly back and forth on the mixing pad. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

122. This process is continued until the mixed paste is uniform in color, with no streaks of the base or catalyst appearing in the mixture. If one of the components is in liquid form, such as the catalyst for condensation silicones, a length of the base is dispensed from the tube onto a graduated mixing pad and drops of the liquid catalyst corresponding to the length of the base are added. The two-putty systems available for condensation and addition silicone are dispensed by volume using an equal number of scoops of each material DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

123. The best mixing technique is to knead the material with one’s fingers until a uniform color is obtained. When the catalyst is a liquid, as in the case of condensation silicones, this kneading procedure with the fingers is applicable. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

124. 124 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

125. STATIC AUTO MIXING The base and catalyst are in separate cylinders of the plastic cartridge. The cartridge is placed in a mixing gun containing two plungers that are advanced by a ratchet mechanism to extrude equal quantities of base and catalyst. The base and catalyst are forced through the static-mixing tip containing a stationary plastic internal spiral; the two components are folded over each other many times as they are pushed through the spiral, resulting in a uniform mix at the tip end DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

126. Because one cylinder may be filled slightly more that the other, the first part of the mix from a new cartridge should be discarded. The mixed material can be extruded directly into an injection syringe or into the impression tray. Intraoral delivery tips can be placed on the end of the static mixing tip, and the mixed material can be injected into and around the cavity preparation. The tip can be removed, and additional mixed material can be extruded into the impression tray. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

127. The automixing systems have been shown to result in mixes with many fewer voids than hand mixes. Although for each mix the material left in the mixing tip is wasted, the average loss is only 1 to 2 mL, depending on the manufacturer’s tip whereas three to four times this much is wasted in a hand mix as a result of overestimating the amount needed. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

128. Initially, automixing was used for low consistencies, but new designs of guns and mixing tips allow all consistencies except putty to be used with this system. Addition silicones, condensation silicon and polyethers are available with this means of mixing. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

129. DYNAMIC MECHANICAL MIXING The catalyst and base are supplied in large plastic bags housed in a cartridge, which is inserted into the top of the mixing machine. A new, plastic mixing tip is placed on the front of the machine, and when the button is depressed, parallel plungers push against the collapsible plastic bags, thereby opening the bags and forcing material into the dynamic mixing tip. This mixing tip differs from auto mixing in that the internal spiral is motor driven so it rotates DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

130. Thus mixing is accomplished by this rotation plus forward motion of the material through the spiral. In this manner, thorough mixing can be ensured and higher viscosity material can be mixed with ease. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

131. Elastomeric impression materials are typically supplied in several viscosities to accommodate different techniques for impression making. Following are the techniques : Multiple-Mix Technique Monophase Technique Putty-Wash Technique IMPRESSION TECHNIQUES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

132. Double mix single impression technique or syringe tray method. Tray used is a special tray and consistencies used are heavy body as a tray material and light body as a syringe material. This technique can be used with polysulphides , polysilicones , polyethers . This method is referred as multiple mix technique because two separate mixtures are required with two separate mixing pads and spatula MULTIPLE MIX TECHNIQUE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

133. 133 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

134. STEPS : The light body material is first mixed and injected into the impression area. Meanwhile the heavy body material is mixed and loaded on the tray and seated over the light body material. The light and heavy body materials set together to give a single impression in which light body material recording all the finer details and supported by the heavy body material . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

135. When both the materials set together, the impression is removed with a steady force to minimise permanent deformation and to maximize tear strength. The impression is cleaned with running tap water, disinfected and the excess water is shaken off and the gentle stream of air is blown to remove the residual moisture. Cast/dye is prepared by pouring type IV dye stone material or type V dye stones. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

136. ADVANTAGES : Less impression material is needed than for the stock trays. Trays are used for single patient, so sterilization is not needed. Uniform thickness of impression material minimizes distortion resulting from thermal and curing shrinkages. Produce dimensionally accurate and stable impression. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

137. DISADVANTAGES : Construction of special trays is time consuming The monomer may be sensitive to some patients These techniques are mainly used for tooth cavity impression for inlays, onlays , crowns, bridges, etc. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

138. Single mix single impression technique. A special tray is used, with rubber adhesive coating. Materials used are of single consistency having pseudoplastic property (regular or light body materials can be used both as a tray and syringe material). This technique is used with addition polysilicones and poly ethers as they have pesudoplastic properties (monophase materials). MONOPHASE TECHNIQUE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

139. The material is mixed and one part of it is loaded into the tray and other part into the syringe. The material is extruded from the syringe onto the prepared tooth surface. Keeping the tip within the material, the syringe is slowly moved all over the prepared area so that the material covers the entire prepared and some of the nonprepared surfaces. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

140. The tray is then placed into the mouth to record the impression. The impression tray generally used for this technique is custom-made resin tray with uniform spacing of 2–4 mm DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

141. Reline technique: Double mix double impression technique, or Putty wash technique Tray used is adhesive treated perforated stock tray Consistencies required are: Putty material for primary impression Light body for secondary impression or corrective wash impression . PUTTY WASH TECHNIQUE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

142. This technique is widely used with condensation and addition polysilicones . It is a two stage method in which the primary impression is taken with putty material and secondary impression is recorded with light body materials DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

143. 143 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

144. 144 DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

145. STEPS: Primary impression : Putty material is placed in a perforated stock trays and the impression is taken before (cavity preparation or crown cutting). Space for the wash material is provided by either cutting away some of the putty material from original impression or by using a spacer between the putty and the teeth when recording the primary impression. When the putty material has set, impression is removed and washed . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

146. STEPS: Secondary/corrective wash impression : After the cavity preparation, the light body material is mixed and injected into the cavity preparation. The tray is reinserted (to act as a custom tray for light with primary impression body) and held gently until the wash material sets. The impression is removed with a steady force, washed, disinfected, dried and dye is poured. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

147. ADVANTAGES : Rapid curing of putty elastomer, that is, the primary impression need to be held in the mouth only for few minutes. Properly used putty wash technique can produce impression with accuracy comparable to that of the multiple mix procedure. Stock trays can be used which eliminate time and expense of fabricating custom trays. Metal stock trays are rigid and not susceptible to distortion. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

148. DISADVANTAGES : It is technique sensitive. Inadequate relief space for wash material. Metal trays must be sterilized. Putty is quite expensive. More impression material is required. This technique is widely used in recording impression for crowns and bridges and prepared cavities for inlays and onlays . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

149. COMMON CAUSES FOR FAILURES OF ELASTOMERIC IMPRESSION MATERIALS DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

150. Incomplete polymerization due to premature removal, and improper mixing Too high accelerator/base paste ratio Too rapid polymerization, by high temperature or humidity . ROUGH OR UNEVEN SURFACE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

151. Rapid polymerization preventing flow Incorporation of air during mixing Inadequate flow . BUBBLES DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

152. Poor adhesion to the tray and detachment of impression. Special tray, gets distorted, if the resin has not completely polymerized Delay in seating of tray causes the mix start polymerizing before seating. Too thick and non uniform impression material. Too much pressure applied continuously even after setting commence . Movement of tray during polymerization. Premature and improper removal of the tray from the mouth. DISTORTION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

153. Inadequate cleaning of impression Excess water or wetting agent left over the impression Too high W/P ratio and improper mixing of the dental stone mix. Premature removal of the stone cast ROUGH OR CHALKY SURFACE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

154. Delay in pouring the cast for polysulphide or condensation polysilicones . Too early pouring the cast (before 20–30 min after taking impressions) in case of additional polysilicones and polyethers . DISTORTION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

155. DISINFECTION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

156. After removal from the patient’s mouth, all impressions should be disinfected since they are contaminated by the oral/body fluids. Depending on the material’s tendency to absorb moisture, the impression is either sprayed with the disinfectant and stored in a plastic bag or immersed in the disinfectant solution. Recommended disinfectant solutions for elastomers except polyethers are glutaraldehyde 2%, chlorine compounds (1:10 dilution of sodium hypochlorite), complex phenolic, and phenolic glutaraldehyde compounds . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

157. disinfection of polyether impressions by immersion is not recommended except for very short (2 to 3minutes) times in chlorine compound disinfectants. Also, the surface quality of high-strength stone dies poured against the impressions is acceptable . DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

158. ADDITION OF SURFACTANT : The use of a more hydrophobic impression material may lead to a high frequency of voids in the cast. It is possible to spray a surfactant on these hydrophobic impressions prior to pouring with gypsum mixtures. A nonionic surfactant such as the one based on a block copolymer of siloxane and ether groups may be added to the bulk of the material during the manufacturing process. The siloxane group is hydrophobic, and this property facilitates dispersion of the surfactant in the bulk of PVS. The ether group is hydrophilic and is oriented toward the surface when the surfactant migrates by diffusion to the surface region. This type of PVS is called a hydrophilized PVS. DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

159. Addition polysilicones and polyethers are used for bite registration for checking the occlusal relationships in the fabrication procedures of dentures (refer bite waxes and ZnOE pastes). Addition polysilicones having similar compositions of light bodies are supplied in automixing cartridges. This has the advantages of adequate flow, negligible resistance, short, suitable setting time, stiffness, good elastic recovery and dimensional stabilities. These are the requirements of bite registration materials. BITE REGISTRATION ELASTOMERS

160. REVIEW OF LITERATURE DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

161. The purpose was t o evaluate the dimensional stability and the detail reproduction of five current elastomeric impression materials in vitro. The materials examined were: 3 different polyether impression materials, a vinyl polysiloxane impression material, and a vinyl polyether silicone impression material. All impression materials were of a medium viscosity . Aivatzidou K, Kamalakidis SN, Emmanouil I, Michalakis K, Pissiotis AL. Comparative Study of Dimensional Stability and Detail Reproduction of Reformulated and Nonreformulated Elastomeric Impression Materials. Journal of Prosthodontics : Official Journal of the American College of Prosthodontists. 2020

162. One stainless steel die was fabricated according to the ANSI/ADA specification no.19 criteria. Twenty impressions of this die were made for each material. Dimensional accuracy and surface detail were evaluated 24 hours after making the impressions using a measuring microscope. The data were analyzed using Welch's analysis of variance, Games‐Howell Post‐Hoc, and the Pearson's chi‐square tests (α = 0.05). Result observed was that t he highest dimensional change was recorded for the vinyl polysiloxane impression material, with a mean percent value of –0.09 ± 0.02% ( p  < 0.001).

163. T he lowest dimensional change was recorded for the Monophase polyether material with a mean percent value of –0.03 ± 0.01% ( p  < 0.038). The best surface detail reproduction results were obtained using the Monophase polyether material (90% acceptable impressions), with no significant differences (χ² [4] = 3.86,  p  = 0.483) observed between the Monophase and the rest impression materials. Conclusion drawn was that a ll impression materials demonstrated acceptable surface detail reproduction with no significant differences between them.

164. T he aim of the study was to assess the disinfection potential of radiofrequency glow discharge (RGD) by microbiological studies. material and methods used were , disinfection potential of RGD on addition silicone ( Reprosil , Dentsply, Milford DE, USA) was assessed. Mathew S, Alani MM, Nair KN, et al. Radiofrequency Glow Discharge as a Mode of Disinfection for Elastomeric Impression Materials. The Journal of Contemporary Dental Practice. 2017 Feb;18(2):131-136..

165. Total sample size was 20. Samples were divided into two groups of 10 each. Group I - control group and group II -RGD-treated group. Main groups were subdivided into subgroups A and B. Data collected were analyzed. Results stated that t he RGD-treated samples were found to be culture sterile which meant that there were no signs of growth of any organisms, thus proving the disinfection potential of RGD .

166. The study concluded that the RGD is a very rapid and handy device, which can disinfect saliva contaminated elastomeric impression material surfaces.

167. CONCLUSION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

168. A good impression is an exact replica of each prepared tooth and should include adequate amount of the unprepared surfaces adjacent to the margin. Elastomeric Impression technique and material should be selected on the basis of biologic factor dictated by the anatomy and the physiology of the mouth. Even though there are innumerable techniques and procedure for impression making ,it is the responsibility of the dentist to select the best possible procedure based on sound knowledge , for achieving the best possible result for the patient. CONCLUSION DEPARTMENT OF PROSTHODONTICS, CROWN AND BRIDGE. DDCH, UDAIPUR

169. REFERENCES

170. Anusavice, K., Phillips, R., Shen, C. And rawls , H., N.D. Phillips' science of dental materials 12 th edition. Bhat sv . science of dental materials : clinical applications 2 nd edition. 2013 Mahalaxmi S . materials used in dentistry . 1 st edition. 2013 John F. Mccabe , angus W.G. Walls . Applied dental materials . 9th edition. 2017 Gladwin M, bagby M. Clinical aspects of dental materials: theory, practice, and cases. 4 th ed. 2013. William J O'Brien .Dental materials selection .3rd edition John m. Powers, john C. Wataha .Dental materials: properties and manipulation, 9 th edition Aivatzidou K, Kamalakidis SN, Emmanouil I, Michalakis K, Pissiotis AL. Comparative Study of Dimensional Stability and Detail Reproduction of Reformulated and Nonreformulated Elastomeric Impression Materials. Journal of Prosthodontics : Official Journal of the American College of Prosthodontists. 2020 Mathew S, Alani MM, Nair KN, et al. Radiofrequency Glow Discharge as a Mode of Disinfection for Elastomeric Impression Materials. The Journal of Contemporary Dental Practice. 2017 Feb;18(2):131-136..