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Elastomeric impression materials / dental implant courses

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
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Elastomeric impression materials / dental implant courses

  1. 1. Elastomers or Rubber base Impression materials www.indiandentalacademy.com INDIAN DENTAL ACADEMY Leader in continuing Dental Education
  2. 2. Introduction  Soft and rubber-like & are known as elastomers or synthetic rubbers.  As per ADA Sp. No. 19 - non-aqueous elastomeric dental impression materials.  Liquid polymers which can be converted into solid rubber at room temperature www.indiandentalacademy.com
  3. 3.  Introduced in late 1950’s – popular drawbacks of hydrocolloids - poor dimensional stability - inadequate tear resistance www.indiandentalacademy.com
  4. 4. Requirements  1. Capable of plastic to rigid body transformation  2. Acceptable for a patient non-toxic, non-irritant, tasteless, reasonable setting time up to 5-7 min  3. Good handling properties – easy to prepare/mix plastic before set, but viscous enough not to flow out of a tray (thixotropic), adequate working and setting times www.indiandentalacademy.com
  5. 5. After being set:  4. Accuracy and detail reproduction (25-50μm),  5. Dimensionally stable  6. Resistant to mechanical stress - elastic and rigid  7. Compatible with model materials  8. Resistant to disinfectant solutions  9. Cost effective www.indiandentalacademy.com
  6. 6. Important terms  Elastic/plastic deformations  Strength  Pseudoplastic/thixotropic  Hydrophilic/hydrophobic  Working time  Setting time www.indiandentalacademy.com
  7. 7. Elastic/plastic deformations www.indiandentalacademy.com
  8. 8. www.indiandentalacademy.com
  9. 9. www.indiandentalacademy.com
  10. 10. Recovery from deformation combination of a spring and a dashpot – a model of viscoelasticity www.indiandentalacademy.com
  11. 11. www.indiandentalacademy.com
  12. 12. Pseudoplasticity/thixotropy of fluids  Property of certain gels or other materials to become liquefied (less viscous) when shaken ,stirred ,patted ,or vibrated- thixotropic.  Character of material to become more fluid when applied force is increased ,shear thinning effect: Pseudoplastic. www.indiandentalacademy.com
  13. 13. Hydrophilic/hydrophobic www.indiandentalacademy.com
  14. 14. Strength www.indiandentalacademy.com
  15. 15. Working time & Setting time  Working time – a period from the start of mixing to the final time at which the impression can be seated in the mouth without its distortion  Setting time – a period from the start of mixing till the impression becomes elastic enough to resist deformation during its withdrawal from the mouth www.indiandentalacademy.com
  16. 16.  Polymerization shrinkage of elastomers is usually compensated for using a combination of:  1. Highly filled-viscous material „Putty“ for preliminary impression (low polymer content - of low shrinkage)  2. Low filled-low viscosity „wash“ or„light“ impression material (high polymer content - higher elasticity but higher shrinkage) www.indiandentalacademy.com
  17. 17.  Setting occurs through a combination of chain lengthening polymerization and chemical cross linking - condensation reaction - addition reaction  The chains of these materials uncoil on stretching and upon removal of the stress they bounce back or snap back to their relaxed entangled state www.indiandentalacademy.com
  18. 18.  Types:  According to chemistry  1) Polysulfides  2) Polysilicones – condensation & addition  3) Polyether  According to Viscosity  1) Light body or syringe consistency  2) Medium or regular body  3) Heavy body or tray consistency  4) Very heavy body or putty consistency  ADA Classification Based on selected elastic properties & dimensional changes 1) Type I 2) Type II 3) Type III www.indiandentalacademy.com
  19. 19. Polysulfide impression materials Composition  Base  polysulfide polymers  fillers  plasticizers  Catalyst  lead dioxide (or copper)  fillers  By-product  water www.indiandentalacademy.com
  20. 20. --SH HS---------------------SH HS-- S H O = Pb = O O = Pb = OO = Pb = O H S -S-S---------------S-S- S S + 3PbO + H2O mercaptan + lead dioxide polysulfide rubber + lead oxide + water Polysulfide Reaction www.indiandentalacademy.com
  21. 21. Properties: 1. Unpleasant odor and colour - stains linen & messy to work with 2. Extremely viscous and sticky - mixing is difficult 3. Mixing time is 45 seconds 4. Long setting time of 12.5 (at 370 C) - Patient discomfort 5. Excellent reproduction of surface detail 6. Dimensional stability: - Curing shrinkage is high 0.45%. - It has the highest permanent deformation (3 to 5%) among the elostomers 7. It is hydrophobic - so the mouth should be dried thoroughly before making an impression 8. It can be electroplated www.indiandentalacademy.com
  22. 22.  Advantages  The best tear strength  Long working time and set time  Good reproduction of surface detail  Good flow before setting  Good bond with tray adhesive  Stable in disinfectant solutions  Relatively inexpensive  Disadvantages  Unpleasant odor and taste  Poor recovery from deformation  Poor dimensional stability  Should be poured within one hour.  Can not be repoured.  Should be used with custom trays  Staining of clothes due to the Lead oxide www.indiandentalacademy.com
  23. 23. Condensation Silicone  Base  poly(dimethylsiloxane)  tetraethylorthosilicate  filler  Catalyst  metal organic ester  By-product  ethyl alcohol Composition www.indiandentalacademy.com
  24. 24. HO – Si – O – Si - O - H CH3 CH3 CH3 CH3 n HO – Si – O – Si - O - H CH3 CH3 CH3 CH3 n C2H5 O OC2H 5 Si C2H5 O OC2H 5 HO – Si – O – Si - O - CH3 CH3 CH3 CH3 n HO – Si – O – Si - O - CH3 CH3 CH3 CH3 n OC2H 5 Si OC2H 5 + 2C2H5OH Setting reaction metal organic ester ethanol Dimethyl + orthoethyl Silicone + ethyl siloxane silicate rubber alcohol www.indiandentalacademy.com
  25. 25.  Properties:  Pleasant odor and color.  Mixing time of 45sec & setting time of 8-9mins.  Excellent reproduction of surface details and highly elastic.  Lesser dimensional stability - high curing shrinkage (0.4 - 0.6%) - permanent deformation due to shrinkage caused by the evaporation of ethyl alcohol is also high (1-3%).  Hydrophobic - needs a dry field.  Electroplatable (silver / copper) and has adequate shelf life).  Biologically inert. www.indiandentalacademy.com
  26. 26.  Advantages  Good recovery from deformation  Good tear strength  Good accuracy  Adjustable working times  No unpleasant odor or taste  Stable in disinfectant solution  Relatively inexpensive  Disadvantages  Hydrophobic: poor moisture compatibility  Poor dimensional stability  Immediate pour required  Poor bond to tray adhesive www.indiandentalacademy.com
  27. 27. A-silicone impression materials Base: Poly (methyl hydrogen siloxane) Other siloxane prepolymers Fillers Accelerator: Divinyl poly siloxane Other siloxane pre polymers Platinum salt: Catalyst (chloroplatinic acid) Palladium or Hydrogen absorber Retarders Fillers Composition: No by product www.indiandentalacademy.com
  28. 28. O H - Si – CH3 O CH3 - Si - H O ---O – Si – CH = CH2 CH3 CH3 CH = CH2 – Si – O --- CH3 CH3 O - Si – CH3 O CH3 - Si - O ---O – Si – CH2 - CH2 CH3 CH3 CH2 - CH2 – Si – O --- CH3 CH3 Chloroplatinic Acid Catalyst Setting reaction www.indiandentalacademy.com
  29. 29.  Properties:  Pleasant odor and color  Excellent reproduction of surface details  Mixing time of 45 secs ,setting time of 5-9 mins.  Best dimensional stability - low curing shrinkage (0.17 %) - lowest permanent deformation (0.05 – 0.3 %)  Stone pouring delayed by 1-2 hours www.indiandentalacademy.com
  30. 30.  Can be electroplated with silver and copper  Good tear strength (300gm / cm2)  Extremely hydrophobic, some manufacturers add a surfactant (detergent) to make it more hydrophilic Surfactants added  reduce contact angle  improved  castability  gypsum  wettability??  still need dry field clinically www.indiandentalacademy.com
  31. 31.  Advantages  Most accurate material available  Good tear strength  Excellent recovery from deformation  Long term dimensional stability  Hydrophilic  No unpleasant taste or odor  Stable in disinfectant solutions  Available in automixing devices www.indiandentalacademy.com
  32. 32.  Disadvantages  Some are hydrophobic  Relatively expensive  Materials are sensitive to contaminants Latex gloves/Rubber dams (Sulfur inhibition) Acrylic temp. residues Heat To manipulate the PUTTY material, DO NOT wear latex gloves. www.indiandentalacademy.com
  33. 33. polyether  Base  difunctional epimine-terminated prepolymer  fillers  plasticizers  Catalyst  aromatic sulfonic acid ester  fillers  Cationic polymerization  ring opening and chain extension Composition www.indiandentalacademy.com
  34. 34.  Polyether + Sulfonic ester  Crosslinked rubber Setting reaction www.indiandentalacademy.com
  35. 35.  Properties:  Pleasant odor and taste  Mixing time is 30 secs, setting time of 8.3 mins  Dimensional stability is very good. Curing shrinkage is low (0.24%) The permanent deformation is also low (1-2%).  Very stiff (flexibility of 3%)  Hydrophillic (moisture control not critical)  Electroplatable with silver & copper www.indiandentalacademy.com
  36. 36.  Advantages  Long term dimensional stability  Good accuracy  Hydrophilic  Good reproduction of surface details  Good tear strength  Rigid  Good bond with tray adhesive  Ease to use Disadvantages Can be too stiff and can cause cast breakage Difficult to mix - spatule May cause allergic reaction Expensive www.indiandentalacademy.com
  37. 37. Impression Material Usage*  Crown & Bridge  vinylpolysiloxane 81%  alginate 38%  polyether 28%  Inlays and Onlays  vinylpolysiloxane 71%  polyether 22%  alginate 20% www.indiandentalacademy.com
  38. 38. Comparison of Properties  Working time:  longest to shortest  agar > polysulfide > silicones > alginate = polyether  Effects of temperature  Increase - both working and setting time decreased by accelerating the curing rate  Decrease - working time increased by refrigerating the materials or mixing on a chilled dry glass slab Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Working Time (min) 7 – 15 2.5 5 – 7 3 2 –4.5 2.5 Setting Time (min) 5 3.5 8 – 12 6 – 8 3 – 7 4.5 Setting time •shortest to longest •alginate < polyether < agar < silicones < polysulfide www.indiandentalacademy.com
  39. 39.  Stiffness:  most to least  polyether > addition silicone > condensation silicone > polysulfide = hydrocolloids Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Flexibility (%) 11 12 8.5 – 20.0 3.5 – 7.8 1.3 – 5.6 1.9 – 3.3 •Problem when dealing with long, thin preparations of periodontally involved teeth • Result in fracture of dies www.indiandentalacademy.com
  40. 40.  Tear strength  greatest to least  polysulfide > addition silicone > polyether > condensation silicone >> hydrocolloids Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Tear Strength (g/cm) 700 380 – 700 2240 – 7410 2280 – 4370 1640 – 5260 1700 - 4800  Important property - in inter proximal and sub gingival areas.  Influenced by  Consistency - increased viscosity increases tear strength  Manner of removal - rapid rate of force during removal increases tear strength www.indiandentalacademy.com
  41. 41. Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Flow (%) -- -- 0.4 – 1.9 < 0.10 < 0.05 < 0.05  Light body materials flow readily into minute details  Tray or heavy body material provide more rigidity to the impression  Early versions of light body tended to flow off the prepared tooth with time - newer PVS and polyether are thixotropic •Flow •Lowest to highest •polyether < addition silicone < condensation silicone <polysulfide www.indiandentalacademy.com
  42. 42.  Dimensional stability  best to worst  addition silicone > polyether > polysulfide > condensation silicone > hydrocolloid Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Shrinkage, 24 hours (%) Extreme Extreme 0.4 – 0.5 0.2 – 1.0 0.01 – 0.2 0.2 – 0.3 stability 1 hour 100% RH Immediate pour 1 hour Immediate pour 1 week 1 week kept dry  Five major sources of dimensional changes  Polymerization shrinkage  Loss of by product (water or alcohol) during condensation reaction  Thermal contraction from oral temperature to room temperature  Imbibition - exposed to water, disinfectant or high humidity environment over a period of time  Incomplete recovery of deformationwww.indiandentalacademy.com
  43. 43.  Elastic recovery:  best to worst  addition silicone > condensation silicone >polyether > agar >alginate >polysulfide Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Elastic Recovery (%) 98.8 97.3 94.5 – 96.9 98.2 – 99.6 99 – 99.9 98.3 – 99.0 A material with 1% permanent deformation has 99% elastic recovery www.indiandentalacademy.com
  44. 44.  Castability  best to worst  hydrocolloids > hydrophilic addition silicone > polyether > polysulfide > hydrophobic addition silicone = condensation silicone Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Wettability and castability Excellent Excellent Fair Fair Fair to good Good Wettability •best to worst •hydrocolloids > polyether > hydrophilic addition silicone > polysulfide > hydrophobic addition silicone = condensation silicone www.indiandentalacademy.com
  45. 45.  Cost  lowest to highest  alginate < agar = polysulfide <condensation silicone < addition silicone < polyether Agar Alginate Polysulfide Condensation Silicone Addition Silicone Polyether Cost Low Very low Low Moderate High to very high Very high www.indiandentalacademy.com
  46. 46.  Regularly-Used Impression Materials Alginate 88% Polyvinyl Siloxane 85% Polyether 27% Other 6% www.indiandentalacademy.com
  47. 47. Summary  Study models  Alginate most widely used  inexpensive  displaces moisture  lower detail reproduction  dimensionally unstable www.indiandentalacademy.com
  48. 48. Summary  Prosthesis  Addition silicones most popular  accurate  dimensionally stable  user friendly  expensive www.indiandentalacademy.com
  49. 49. Manipulation  Uniform bulk of materials  Adhesion of impression tray to the material  Pouring of impression materials  Viscosity control  Adequate mixing DCNA 2004www.indiandentalacademy.com
  50. 50. TRAYS  All impression materials shrink upon setting  Reversible hydrocolloid - a thermoplastic  Elastomers - polymerization shrinkage  Accurate impression - uniform amount of bulk in the impression is imperative - uniform shrinkage throughout the body of the impression DCNA 2004www.indiandentalacademy.com
  51. 51.  Reversible or Irreversible hydrocolloid -maximum accuracy with a cross sectional thickness of 4-6 mm - Stock trays  Elastomeric impressions - most accurate when used with a cross sectional thickness of 2 mm - Custom tray DCNA 2004www.indiandentalacademy.com
  52. 52. Stock trays Stock plastic trays Stock metal trays Clear trays •Non-perforatedNon-perforated •PerforatedPerforated •Rim lock traysRim lock trays •Non-perforatedNon-perforated •PerforatedPerforated •Dual arch traysDual arch trays Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  53. 53. www.indiandentalacademy.com
  54. 54.  Stock plastic trays  One or two single units  Do not have sufficient rigidity  Not expensive  Contra indicated - fixed bridge work - flexibility adversely affects inter preparation, cross arch and anteroposterior dimensions Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  55. 55.  Stock metal trays  Coated steel or stainless steel - combine the convenience of stock plastic trays with the rigidity of custom trays.  Perforated or rim lock trays – basically used for mechanical retention in addition to tray adhesives Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  56. 56.  Custom trays  Custom tray improves the accuracy of an elastomeric impression by limiting the volume of the material  Reducing two sources of error  Stresses during removal  Polymerization shrinkage Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  57. 57. Fabrication  Custom trays - constructed on the diagnostic cast using a layer of base plate wax as the spacer  Polymethylmethacrylate  Photo-cure bisacryl materials (Triad)  PVS putty materials  Thermoplastic trays Fundamentals of fixed prosthodontic 3rd ed :Shilingburg www.indiandentalacademy.com
  58. 58.  PMM trays should be fabricated at least 24 hours in advance - stability  Tray should extend 3-5 mm from gingival margin  Wax spacer covered with tin foil to permit easy removal of the spacer from the tray Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  59. 59.  DUAL ARCH TRAYS  Trays are available in both anterior and posterior designs and consist of an outer rim that is spanned by a mesh fabric  Any elastic impression material - more rigid- bodied materials are preferred Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  60. 60.  If bucco - lingual width of the alveolar ridge is wider than the width of the tray - outer rims will be wedged apart when the patient closes into the impression material – resulting in distorted impression - tray can be modified by cutting the mesh Fundamentals of fixed prosthodontic 3rd ed :Shilingburgwww.indiandentalacademy.com
  61. 61. Tray adhesive www.indiandentalacademy.com
  62. 62.  Liquid rubber (e.g. butyl rubber) dissolved in a volatile solvent such as chloroform or ketone  Silicones :polydimethyl siloxane & ethyl silicate  Form an adhesive bond to the tray  Roughening the surface of custom trays increases the adhesive bond strength  Painted in a thin layer on the internal surface of the tray and the tray borders atleast 7-15 minutes before making the impression W.Patrick :An overview of impression materials vol4www.indiandentalacademy.com
  63. 63. Mixing:  Paste form -> equal lengths of base and reactor paste taken over the mixing pad - reactor paste is first spread over the base paste, mixing continued until a smooth, homogenous, streak free mix is obtained.  When reactor supplied in liquid form -> number of drops per unit length are recommended by manufacturer.  Two putty system -> kneaded between the fingers O’Brien dental materials and their selection 3rd ed www.indiandentalacademy.com
  64. 64. Automatic Mixing devices www.indiandentalacademy.com
  65. 65.  Used for light and medium viscosity materials  prepackaged cartridges  disposable mixing tip  The cartridge inserted in a gun like device, and base and catalyst are extruded into the spiral mixing tip, where mixing occurs as they progress to the end of the tube. Philip’s science of dental materials 11th edwww.indiandentalacademy.com
  66. 66.  Advantages  Greater uniformity in proportioning and in mixing.  Less air incorporated into the mix.  Mixing time reduced.  Less chance of mix getting contaminated  Less wastage of material. Philip’s science of dental materials 11th edwww.indiandentalacademy.com
  67. 67. Dynamic mechanical mixer Internet sources www.indiandentalacademy.com
  68. 68.  The device uses a motor to drive parallel plungers that force the materials into a mixing tip, and the spiral inside the mixing tip rotates as the material are extruded through the tip  Higher viscosity material can be mixed Internet sourceswww.indiandentalacademy.com
  69. 69.  Effects of mishandling elastomers  Rough or uneven surface on impression  Bubbles  Irregularly shaped voids  Rough or chalky stone cast  Distortion Philip’s science of dental materials 11th edwww.indiandentalacademy.com
  70. 70.  RECENT ADVANCES IN ELASTOMERS www.indiandentalacademy.com
  71. 71. Visible light cured impression material: • Polyether urethane dimethacrylate. • Introduced early 1988 by GENESIS and L D CAULK. • Two viscosities: Light and heavy. W.Patrick :An overview of impression materials vol4www.indiandentalacademy.com
  72. 72. Properties: • Long working time and short setting time. • Blue light is used for curing with transparent impression trays. • Tear strength – 6000 to 7500 gm/cm (Highest among elastomers) • Other properties are similar to addition silicone. W.Patrick :An overview of impression materials vol4www.indiandentalacademy.com
  73. 73. Manipulation: • Both light body and heavy body are cured with visible light having 8 mm or larger diameter probe. • Curing time approx 3 min. Adv: - Controlled working time - Excellent properties Disadv: - Special transparent trays - Difficult to cure in remote area W.Patrick :An overview of impression materials vol4www.indiandentalacademy.com
  74. 74. Duplicating materials  Hydrocolloids are used to duplicate dental casts or models - construction of prosthetic appliances and orthodontic products  Reversible (Agar) Hydrocolloid  Same composition as impression material - water content is higher  Classification (ANSI/ADA specification No.20)  Type I – Thermo reversible  Type II – Non reversible  Silicones and polyether - expensive Craig’s restorative dental materials 12th ed www.indiandentalacademy.com
  75. 75. Review of literature:  Pre and post set hydrophilicity of impression materials were evaluated (j prosth 2007)  Hydrophilicity of one polyether,4 A silicone & 1 C silicone were evaluated pre and post setting under simulated conditions.  Polyether showed smallest contact angle  Polyether was most hydrophilic of the materials tested. www.indiandentalacademy.com
  76. 76.  Mechanical properties of elastomeric impression materials (H LU, B NGUYEN - 2004 )  Mechanical properties of three commercial elastomeric impression materials two addition silicone impression materials and one polyether material with low and high viscosities were compared.  All the products had similar elastic recovery and quite different other properties.  Polyether had higher strain-in-compression and less tensile strength compared to addition silicone materials.  Heavy-body materials had higher tear properties and tensile strength than light-body www.indiandentalacademy.com
  77. 77. The effect of different adhesives on vinyl polysiloxane bond strength to two tray materials.(J of prosth 2005)  evaluate the bond of 3 VPS materials with a methylmethacrylate auto polymerizing and a light-polymerizing tray material, using the adhesive recommended by the manufacturer of the impression material, and 2 universal adhesives (paint-on and spray-on).  universal spray-on adhesive consistently demonstrated significantly lower bond strengths than all other adhesives (P<.05). Equivalent or significantly (P<.05) higher bond strength values were found for the universal paint-on adhesive for the 3 impression materials tested. www.indiandentalacademy.com
  78. 78.  Compare surface detail reproduction between various combinations of contemporary addition-reaction silicone impression materials and Type IV gypsum products.(J of prosth 2005)  All impression materials tested fully reproduced the 20-Mm line.  Different impression materials showed different compatibility with different Type IV gypsum products.  Not all of impression material and Type IV gypsum products used exhibited similar compatibility. www.indiandentalacademy.com
  79. 79. Distortion of disposable plastic stock trays when used with putty vinyl polysiloxane impression materials. (J of prosth 2005)  Rigidity and ability to resist deformation of 6 commercially available disposable plastic stock trays and 1 metal stock tray when used in conjunction with a high-viscosity vinyl polysiloxane impression material.  disposable plastic trays tested were not sufficiently rigid to resist deformation when used with very high-viscosity putty material. Metal stock trays showed significantly less change in cross-arch dimension than plastic trays www.indiandentalacademy.com
  80. 80. Impression Accuracy of Sectional Stock Tray System(Prosthodontic Research & Practice 2004)  Evaluated the accuracy of a sectional stock tray for making impressions.  Making impressions was easier with sectional stock tray. There were no significant differences (p>0.10) between the sectional stock tray and a conventional stock tray. www.indiandentalacademy.com
  81. 81. Conclusion The ability to record consistently good impressions is both a science and an art. Impression techniques, methods and materials are evolving and changing but underlying principles and fundamentals remain constant. An ideal impression must be in the mind of the dentist before it can be in his hand. It is this knowledge and experience that enables a dentist to create desirable results www.indiandentalacademy.com
  82. 82. www.indiandentalacademy.com

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