elastomeric impression dental material

Download elastomeric Impression DENTAL material

Post on 24-Dec-2014

915 views

Category:

Education

2 download

Embed Size (px)

DESCRIPTION

elastomeric Impression DENTAL material

TRANSCRIPT

  • 1. Elastomeric Impression Materials

2. Elastomeric = Rubber-like polymers that show an elastic behavior at the time of load application These polymer molecules have weak interaction in between (Van der Wall forces), although they are tied together in 3D network. On stretching (on loading) chains uncoil At rest (off loading) chains snap back ChemicalNature 3. Higher tear strength More stable dimensionally in storage (No Synersis, Imbibation or Evaporation) Ability to be electroplated But, Quite Expensive !!!!But, Quite Expensive !!!! Incomparisonto hydrocolloids 4. Elastomeric impression materials Polysulfide (hydrophobic) Silicones Polyether (hydrophilic) Condensation Silicone (hydrophobic) Addition silicone Hydrophobic type Hydrophilic type Fourdifferent types 5. Presentation forms Materials Consistency Light Medium Heavy Putty Silicone materials only 6. Polysulfide RubberPolysulfide Rubber Impression MaterialImpression Material 7. CHEMISTRY A. Composition: Base paste 1. LMW Polysulfide with two terminal and one pendant SH groups 2. Fillers (Titanium dioxide) 3. Plasticizer (Dibutyl phethalate) Catalyst paste 1. Lead dioxide (Brown) or organic peroxides (Gray) reactor 2. Fillers (Titanium dioxide) 3. Plasticizer (Dibutyl phethalate) Polysulfide Rubber 8. Polysulfide Rubber B. Setting Reaction: +Pb+H2o HS----R----SH HS----R----SH SH SH+ PbO2 +Pb+H2o HS----R----SH HS----R----SH SH SH+ PbO2 HS----R----SH HS----R----SH SH SH+ PbO2 Condensation polymerization (exothermic + shrinkage) with releasing of H2O as reaction by-product It occurs as a series of simple oxidation reactions Oxidation of terminal SH groups polymer chains Oxidation of pendent SH groups Cross-linking 9. Material sets via condensation polymerization reaction Water is the reaction by-product Evaporation of water + polymerization shrinkage Dimensional changes in storage Water could cause air bubbles in stone cast Polysulfide is hydrophobic, and can be electroplated Lead dioxide is toxic and has bad smell, so it has been replaced in recent products by peroxide compounds Polysulfide Rubber OBVIOUS CHARACTERS 10. Condensation SiliconeCondensation Silicone Impression MaterialImpression Material 11. CHEMISTRY A. Composition: Base paste 1. LMW silicone polymer with terminal OH groups 2. Fillers (Colloidal silica or titanium dioxide) (white) Catalyst paste 1. Alkyl silicate (Cross linking) 2. Tin dilaurate or Stannous octoate (Activator) Condensation Silicone 12. HO Si - O - Si OH + CH3 CH3 CH3 CH3 Si C2H5OC2H5O C2H5O C2H5O C2H5OH+ HMW Silicon Polymer Ethyl Alcohol Dimethyl Siloxane Alkyl Silicate Stanous Octoate HO Si - O - Si OH + CH3 CH3 CH3 CH3 Si C2H5OC2H5O C2H5O C2H5O C2H5OH+ HMW Silicon Polymer Ethyl Alcohol Dimethyl Siloxane Alkyl Silicate Stanous Octoate HO Si - O - Si OH + CH3 CH3 CH3 CH3 HO Si - O - Si OH + CH3 CH3 CH3 CH3 Si C2H5OC2H5O C2H5O C2H5O Si C2H5OC2H5O C2H5O C2H5O C2H5OH+ HMW Silicon Polymer Ethyl Alcohol Dimethyl Siloxane Alkyl Silicate Stanous Octoate B. Setting Reaction: Condensation poly-merization (exothermic + shrinkage) releasing C2H5OH as reaction by-product It occurs as a series of cross-linkage of siloxane polymer to alkyl silicate in presence of the activator, to form a 3D polymer network Condensation Silicone 13. Material sets via condensation polymerization reaction Ethyl alcohol is the reaction by-product Evaporation of alcohol + polymerization shrinkage Dimensional changes in storage > that of polysulfide Alcohol could cause air bubbles in stone cast Cond. silicone is hydrophobic, and can be electroplated either with silver or copper Condensation Silicone OBVIOUS CHARACTERS 14. Addition SiliconesAddition Silicones Impression MaterialsImpression Materials 15. AdditionSilicones CHEMISTRY A. Composition: Base paste 1. Poly methyl hydrogen siloxane (Hydried or silane terminated silicone) 2. Other Siloxane pre-polymers 3. Fillers Catalyst paste 1. Divinyl poly(dimethyl siloxane) 2. Platinum salt activator (Chloroplatinic acid) 3. Siloxane pre-polymers 4. Fillers 16. B. Setting Reaction: Addition polymerization (exothermic + shrinkage) with no release of by-product It occurs as a series of cross-linkage between vinyl- terminated silicon and silane-terminated (hydried) silicon molecules, in presence of the catalyst (platinum salt) to form a 3D polymer network A side reaction (Releasing hydrogen gas Air bubbles in gypsum cast) may occur if : 1. No balance between vinyl siloxane and the hydried silicone 2. Moisture react with hydrides of the base polymer Adding noble metal (platinum or palladium) to the composition will act as hydrogen absorber AdditionSilicones 17. Adding surfactants (surface tension reducing agents) to the composition of add. silicone help turns the material to be hydrophilic (water lover) Advantages: 1. Better wetting of soft tissue registration of better details 2. Air bubbles in gypsum cast Disadvantages: 1. Difficult to be electroplated 2. Setting reaction could be retarded in presence of sulfur (in latex gloves) or sulfate compounds (in gingival retraction cords) HYDROPHILIC SILICONEAdditionSilicones 18. Material sets via Addition polymerization reaction (No by-product) More dimensionally stable than condensation-polymerized materials Hydrogen gas may release from a side reaction in presence of moisture or imbalance of the reactants. But, adding noble metal to the composition prevents the release of hydrogen gas no air bubbles in the gypsum cast Add.silicone is hydrophobic and can be electroplated, however adding of surfactants turns the material hydrophilic AdditionSilicones OBVIOUS CHARACTERS 19. Polyether RubberPolyether Rubber Impression MaterialImpression Material 20. CHEMISTRY A. Composition: Base paste 1. LMW polyether with terminal imine groups 2. Filler (colloidal silica) 2. Plasticizer (dibutyl phethalate or glycoether) Catalyst paste 1. Aromatic sulfonate reactor (Sulfonic acid ester) 2. Fillers 3. Plasticizer PolyetherRubber 21. CHEMISTRY B. Reaction: (Cont.d) Material sets via ring opening addition poly- merization reaction (No by-product) of imine- terminated polyether with the aromatic sulfonate LIGHT-CURED POLYETHER It is based on polyether-urethane dimethacrylate, photo-initiator, accelerator, and silicone filler (has refractive index similar to resin that helps in maximizing the depth of curing) This material is no longer be used PolyetherRubber 22. Material sets via Addition polymerization reaction (No by-product) More dimensionally stable than condensation polymerized materials Set material is so stiff (as a result of high rate of crosslinking), so tray adhesive must be used to retain the material within the tray at the time of removing an impression Polyether is hydrophilic and can absorb water in wet condition (swelling), accordingly Can not be electroplated should be stored in dry environment to preserve its dimensional accuracy OBVIOUS CHARACTERSPolyetherRubber 23. Comparative PropertiesComparative Properties of Elastomeric Impressionof Elastomeric Impression MaterialsMaterials 24. Biological properties: 1. Lead dioxide (polysulfide) is toxic, but following the manufacturers instruction will decrease this risk 2. Alcohol by-product (cond. Silicone) is irritant to oral soft tissues 3. Aromatic sulfonate (polyether) is irritant, but proper mixing will decrease this irritability Comparative Properties 25. Interfacial properties: 1. Hydrophilicity Polysulfide, cond. Silicone, & add. Silicone are hydrophobic Hydrophilic silicone and polyether are Hydrophilic 2. Compatibility with model and die materials... Hydrophilic materials can not be electroplated Polysulfide could be electroplated with silver, while silicones could be electroplated either with silver or copper hydrophobic materials may cause air bubbles in stone casts Comparative Properties 26. Interfacial properties: (cont.d) 3. Separating media There is no need (elastic materials) for separating medium before pouring the cast 4. Detail reproduction Although, hydrophilic materials show better registration of details than hydrophobic ones, Polysulfide is the best detail reproducer due to its higher flow rate Comparative Properties 27. Mechanical properties: 1. Flexibility... Polysulfide > Cond. Silicone > add. Silicone > polyether 2. Flow... Polysulfide > Cond.silicone > Polyether > Add. Silicone 3. Permanent deformation Polysulfide > Cond.silicone > Polyether > Add. Silicone 4. Tear strength Polyether > polysulfide > silicones 5. Recovery Rubber materials are viscoelastic, so impressions should be poured 30 min after removal from the patient mouth in order to get the whole elastic and delayed recovery of imp.mat. Comparative Properties 28. Chemical properties: 1. Dimensional changes Cond. silicone > polysulfide > Polyether > add silicone All materials are associated with setting (polymerization) shrinkage All condensation polymerized materials are less stable in storage as a result of evaporation of the reaction by- product 2. Odor Lead dioxide-containing polysulfide has bad smell Comparative Properties 29. Practicability: 1. Mixing time... (45 sec.- 1 min.) 2. Working time... (average 5 min.) 3. Setting time... (average 8-12 min) 4. Coast... higher than hydrocolloids 5. Shelf lifestorage in refrigerator elongate the shelf life 6. Disinfection could be done either by spray or short immersion technique using NaOCl, Iodofore or Glutaraldehyde. Care should be expressed with hydrophilic materials (not immersed for long time) Comparative Properties 30. Materials ManipulationMaterials Manipulation Manipulation 31. Mixing: 1. Using paper pad (Glass slab) and Spatula Light, medium and heavy consistencies 2. Hand Kneading Heavy or putty consistency 3. Automixer and Dispenser Cartridge form only (L

Recommended

View more >