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Impression Materials

Impression Materials. Impression Materials. Non-elastic Elastic Aqueous hydrocolloids Agar Alginate Non-aqueous elastomers Polysulfide Silicones Condensation Addition Polyether. Indications. Diagnostic casts preliminary opposing Indirect reconstruction fixed removable

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Impression Materials

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  1. Impression Materials www.rxdentistry.blogspot.com

  2. Impression Materials • Non-elastic • Elastic • Aqueous hydrocolloids • Agar • Alginate • Non-aqueous elastomers • Polysulfide • Silicones • Condensation • Addition • Polyether www.rxdentistry.blogspot.com

  3. Indications • Diagnostic casts • preliminary • opposing • Indirect reconstruction • fixed • removable • Bite registration Giordano, Gen Dent 2000 www.rxdentistry.blogspot.com

  4. Elastomeric Impression Materials • Viscoelastic • physical properties vary • rate of loading • Rapidly remove • decreases permanent deformation • chains recoil from a recoverable distance • increases tear strength Phillip’s Science of Dental Materials 1996 www.rxdentistry.blogspot.com

  5. Plaster Compound Waxes ZnO - Eugenol Polysulfide Silicones Polyether Non-elastic Impression Materials Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Condensation Non-aqueous Elastomers Addition O’Brien, Dental Materials & their Selection 1997 www.rxdentistry.blogspot.com

  6. Aqueous Hydrocolloids • Colloidal suspensions • chains align to form fibrils • traps water in interstices • Two forms • sol • viscous liquid • gel • elastic solid • Placed intra-orally as sol • converts to gel • thermal or chemical process Phillip’s Science of Dental Materials 1996 www.rxdentistry.blogspot.com

  7. Aqueous Hydrocolloids • Semi-permeable membranes • poor dimensional stability • Evaporation • Syneresis • fibril cross linking continues • contracts with time • exudes water • Imbibition • water absorption • swells Phillip’s Science of Dental Materials 1996 www.rxdentistry.blogspot.com

  8. Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Polysulfide Condensation Non-aqueous Elastomers Silicones Addition Polyether O’Brien, Dental Materials & their Selection 1997 www.rxdentistry.blogspot.com

  9. Reversible Hydrocolloid (Agar) • Indications • crown and bridge • high accuracy • Example • Slate Hydrocolloid (Van R) www.rxdentistry.blogspot.com

  10. cool to 43ºC agar hydrocolloid (hot) agar hydrocolloid (cold) (sol)(gel) heat to 100ºC Composition • Agar • complex polysaccharide • seaweed • gelling agent • Borax • strength • Potassium sulfate • improves gypsum surface • Water (85%) O’Brien, Dental Materials & their Selection 1997 www.rxdentistry.blogspot.com

  11. Manipulation • Gel in tubes • syringe and tray material www.rxdentistry.blogspot.com

  12. Manipulation • 3-chamber conditioning unit • (1) liquefy at 100°C for 10 minutes • converts gel to sol • (2) store at 65°C • place in tray • (3) temper at 46°C for 3 minutes • seat tray • cool with water at 13°C for 3 minutes • converts sol to gel O’Brien, Dental Materials & their Selection 1997 www.rxdentistry.blogspot.com

  13. Advantages • Dimensionally accurate • Hydrophilic • displaces moisture, blood, fluids • Inexpensive • after initial equipment • No custom tray or adhesives • Pleasant flavor • No mixing required Phillip’s Science of Dental Materials 1996 www.rxdentistry.blogspot.com

  14. Disadvantages • Initial expense • special equipment • Material must be prepared in advanced • Tears easily • Dimensionally unstable • Must be poured immediately • Can only be used for a single cast • Difficult to disinfect Phillip’s Science of Dental Materials 1996 www.rxdentistry.blogspot.com

  15. Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Polysulfide Condensation Non-aqueous Elastomers Silicones Addition Polyether O’Brien, Dental Materials & their Selection 1997 www.rxdentistry.blogspot.com

  16. Irreversible Hydrocolloid (Alginate) • Most widely used impression material • Indications • study models • removable fixed partial dentures • framework • Examples • Jeltrate (Dentsply/Caulk) • Coe Alginate (GC America) Phillip’s Science of Dental Materials 1996 www.rxdentistry.blogspot.com

  17. 2 Na3PO4 + 3 CaSO4 Ca3(PO4)2 + 3 Na2SO4 H2O Na alginate + CaSO4 Ca alginate + Na2SO4 (powder) (gel) Composition • Sodium alginate • salt of alginic acid • mucous extraction of seaweed (algae) • Calcium sulfate • reactor • Sodium phosphate • retarder • Filler • Potassium fluoride • improves gypsum surface www.rxdentistry.blogspot.com O’Brien Dental Materials & their Selection 1997

  18. Manipulation • Weigh powder • Powder added to water • rubber bowl • vacuum mixer • Mixed for 45 sec to 1 min • Place tray • Remove 2 to 3 minutes • after gelation (loss of tackiness) www.rxdentistry.blogspot.com Caswell JADA 1986

  19. Advantages • Inexpensive • Easy to use • Hydrophilic • displace moisture, blood, fluids • Stock trays www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  20. Disadvantages • Tears easily • Dimensionally unstable • immediate pour • single cast • Lower detail reproduction • unacceptable for fixed pros • High permanent deformation • Difficult to disinfect www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  21. Non-Aqueous Elastomers • Synthetic rubbers • mimic natural rubber • scarce during World War II • Large polymers • some chain lengthening • primarily cross-linking • Viscosity classes • low, medium, high, putty • monophasic www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  22. Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Polysulfide Condensation Non-aqueous Elastomers Silicones Addition Polyether www.rxdentistry.blogspot.com O’Brien Dental Materials & their Selection 1997

  23. Polysulfide • First dental elastomers • Indications • complete denture • removable fixed partial denture • tissue • crown and bridge • Examples • Permlastic (Kerr) • Omni-Flex (GC America) www.rxdentistry.blogspot.com

  24. Composition • Base • polysulfide polymers • fillers • plasticizers • Catalyst • lead dioxide (or copper) • fillers • By-product • water www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  25. O O = = mercaptan + lead dioxide polysulfide rubber + lead oxide + water Pb Pb = = O O Polysulfide Reaction --SH HS---------------------SH HS-- -S-S---------------S-S- S S + 3PbO + H2O H S O = Pb = O H S www.rxdentistry.blogspot.com O’Brien Dental Materials & their Selection 1997

  26. Manipulation • Adhesive to tray • Uniform layer • custom tray • Equal lengths of pastes • Mix thoroughly • within one minute • Setting time 8 – 12 minutes • Pour within 1 hour www.rxdentistry.blogspot.com

  27. Advantages • Lower cost • compared to silicones and polyethers • Long working time • High tear strength • High flexibility • Good detail reproduction www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  28. Disadvantages • Poor dimensional stability • water by-product • pour within one hour • single pour • Custom trays • Messy • paste-paste mix • bad odor • may stain clothing • Long setting time www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  29. Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Polysulfide Condensation Non-aqueous Elastomers Silicones Addition Polyether www.rxdentistry.blogspot.com O’Brien Dental Materials & their Selection 1997

  30. Condensation Silicone • Indications • complete dentures • crown and bridge • Examples • Speedex (Coltene/Whaledent) • Primasil (TISS Dental) www.rxdentistry.blogspot.com

  31. Composition • Base • poly(dimethylsiloxane) • tetraethylorthosilicate • filler • Catalyst • metal organic ester • By-product • ethyl alcohol Phillip’s 1996 www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  32. C2H5O OC2H5 Si C2H5O OC2H5 CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 HO – Si – O – Si - O - H HO – Si – O – Si - O - H HO – Si – O – Si - O - HO – Si – O – Si - O - CH3 CH3 CH3 CH3 CH3 CH3 CH3 CH3 n n n n OC2H5 + 2C2H5OH Si OC2H5 CondensationSilicone Reaction metal organic ester ethanol www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  33. Manipulation • Mix thoroughly • paste - paste • paste - liquid • Putty-wash technique • reduces effect of polymerization shrinkage • stock tray • putty placed • thin plastic sheet spacer • preliminary impression • intraoral custom tray • inject wash material www.rxdentistry.blogspot.com

  34. Advantages • Better elastic properties • Clean, pleasant • Stock tray • putty-wash • Good working and setting time www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  35. Disadvantages • Poor dimensional stability • high shrinkage • polymerization • evaporation of ethanol • pour immediately • within 30 minutes • Hydrophobic • poor wettability www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  36. Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Polysulfide Condensation Non-aqueous Elastomers Silicones Addition Polyether www.rxdentistry.blogspot.com O’Brien Dental Materials & their Selection 1997

  37. Addition Silicones • AKA: Vinyl polysiloxane • Indications • crown and bridge • denture • bite registration • Examples • Extrude (Kerr) • Express (3M/ESPE) • Aquasil (Dentsply Caulk) • Genie (Sultan Chemists) • Virtual (Ivoclar Vivadent) www.rxdentistry.blogspot.com

  38. Composition • Improvement over condensation silicones • no by-product • First paste • vinyl poly(dimethylsiloxane)prepolymer • Second paste • siloxane prepolymer • Catalyst • chloroplatinic acid Phillip’s 1996 www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  39. O O - Si – CH3 H - Si – CH3 CH3 CH3 O O CH2 - CH2 – Si – O --- CH = CH2 – Si – O --- CH3 - Si - H CH3 - Si - CH3 CH3 O O CH3 CH3 ---O – Si – CH2 - CH2 ---O – Si – CH = CH2 CH3 CH3 Addition Silicone Reaction Chloroplatinic Acid Catalyst www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  40. Manipulation • Adhesive to tray • Double mix • custom tray • heavy-body • light-body to prep • Putty-wash • stock tray www.rxdentistry.blogspot.com Craig Adv Dent Res 1988

  41. Advantages • Highly accurate • High dimensional stability • pour up to one week • Stock or custom trays • Multiple casts • Easy to mix • Pleasant odor www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  42. Disadvantages • Expensive • Sulfur inhibits set • latex gloves • ferric and Al sulfateretraction solution • Pumice teeth beforeimpressing • Short working time • Lower tear strength • Possible hydrogen gas release • bubbles on die • palladium added to absorb www.rxdentistry.blogspot.com Manikos Aust Dent J 1998

  43. Addition Silicones • Surfactants added • reduce contact angle • improved • castability • gypsum • wettability?? • still need dry field clinically Pratten J Dent Res 1987 Mandikos Aust Dent J 1998 www.rxdentistry.blogspot.com

  44. Agar (reversible) Aqueous Hydrocolloids Alginate (irreversible) Elastic Polysulfide Condensation Non-aqueous Elastomers Silicones Addition Polyether www.rxdentistry.blogspot.com O’Brien Dental Materials & their Selection 1997

  45. Polyether • Indications • crown and bridge • bite registration • Examples • Impregum F (3M/ESPE) • Permadyne (3M/ESPE) • Pentamix (3M/ESPE) • P2 (Heraeus Kulzer) • Polygel (Dentsply Caulk) www.rxdentistry.blogspot.com

  46. Composition • Base • difunctional epimine-terminated prepolymer • fillers • plasticizers • Catalyst • aromatic sulfonic acid ester • fillers • Cationic polymerization • ring opening and chain extension www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  47. CH3 – CH – CH2 – CO2 – CH – (CH2)n – O – CH – (CH2)n – CO2 –CH2 – CH –CH3 R R m + R+ N N N N N H2C H2C H2C H2C H2C CH2 CH2 CH2 CH2 CH2 SO3- R – + R – N – CH2 – CH2 – + + Polyether Reaction base catalyst ring opening www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  48. Manipulation • Adhesive to tray • stock or custom tray • very stiff • Paste-paste mix • Auto-mixing • hand-held • low viscosity • mechanical dispenser • high viscosity www.rxdentistry.blogspot.com

  49. Advantages • Highly accurate • Good dimensional stability • Stock or dual-arch trays • Good surface detail • Pour within one week • kept dry • Multiple casts • Good wettability www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

  50. Disadvantages • Expensive • Short working time • Rigid • difficult to remove from undercuts • Bitter taste • Low tear strength • Absorbs water • changes dimension www.rxdentistry.blogspot.com Phillip’s Science of Dental Materials 1996

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