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Impression materials 2.pptx
- 1. IMPRESSION MATERIALS PART -2 Dr. shiva sai
- 2. Based on mechanical properties Elastic Nonelastic or rigid softtissue Mucostatic Mucocompressive Selective pressure nature of hardening physical change chemical change Viscosity High viscosity Medium viscosity Low viscosity Dispensing system Cakes, cylinders, sticks, and cones Powder Two-paste system Three-paste system Single paste system clinical applications Preliminary Secondary
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- 6. Classification of impressionmaterials setting mechanism Inelasticity elasticity
- 7. PLASTICIZERS • It reducesstrength and hardness. • It reduces glass transition temperature of a polymer. • It increases polymer flexibility and flow characteristics. PLASTICIZER External Plasticizers physically blended with the polymer and do not enter the polymerization reaction but are distributed throughout the polymerized mass. Internal Plasticizers plasticizer does not leach out and the material remains more flexible
- 8. FILLERAND PLASTICIZER Filler = increases strengthand hardness Filler = ground nuts Plasticizer = jaggery filler α 1/plasticizer
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- 10. Impression Compound ADA SpecificationNumber – 3 Alternative Names • • Dental compound • • Model compound • • Model plastic
- 12. Impression compound Type I Lowfusing Impression compound Green stick compound Type II high fusing Tray compound
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- 14. Properties •Biological Properties •Rheological Properties •ThermalProperties •Mechanical Properties
- 15. Manipulation Softening • 55°C–60°C Kneading • toobtain uniform plasticity Loading • Placing in impression tray Tempering • Immersing in hot and cold water Making impression • cools to mouth temperature
- 16. Softening • 55°C–60°C Kneading • toobtain uniform plasticity Loading • Placing in impression tray Tempering • Immersing in hot and cold water Making impression • cools to mouth temperature
- 17. Advantages • compressing softtissues. • close peripheral seal. • Can be used in combination with other materials. • added and readopted. • Relatively cheap. Disadvantages • Distorts easily and should not be used when undercuts exist. • Does not reproduce fine surface detail. • Can only give an accurate impression • unhygienic since it cannot be sterilised • large COTE and low thermal conductivity
- 18. Uses • Used forrecording preliminary impressions of edentulous arches for the construction of special trays
- 19. Green Stick Compound •ADA- 3 •The composition of green stick compound is almost similar to that of impression compound with more plasticizers. It is softened by waving over a gas flame and kneaded (dry kneading).
- 21. Copper RingTechnique orTubeImpressionTechnique
- 22. Uses • It isused for border extensions of special trays (border molding technique). •To obtain an impression of single tooth preparations using copper band. • Peripheral seal material
- 23. Tray Compound • ADA-3 •They are similar in composition and working qualities to the impression compound except that the temperature at which they soften, i.e. higher (70° C) and the property of flow at mouth temperature is minimal (less than 2%).
- 24. USES • used toprepare custom made preliminary impression (special tray) that will later hold a second impression material, which will record final impression (secondary impression). • NOTE:- • Tray compounds lack strength and dimensional stability; hence they have been replaced to a large extent by trays made from self-cure acrylic resins.
- 25. Zinc Oxide EugenolImpression Paste • ADA Specification Number: 16 Types Type I – Hard Type II – Soft
- 26. Dispensing • Usually suppliedas two pastes in collapsible metal tubes .Tube-1 is base (white in color) and tube-2 is reactor (red in color).They are also available in powder (ZnO) and liquid (Eugenol) system
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- 31. • On mixingthe two pastes, a reaction between zinc and eugenol begins.The basis of the reaction is that the phenolic – OH groups of eugenol acts as a weak acid and undergoes an acid-base reaction with ZnO to form a salt, “zinc eugenolate”. • it can be seen that ionic salt bonds are formed between zinc and phenolic oxygen of each molecule of eugenol.Two further coordination bonds formed by donation of a pair of electrons form methoxyoxygen to zinc. • Water is needed to initiate the reaction and it is also a byproduct of the reaction.This type of reaction is often called “auto catalyzation”.
- 32. Acid - basereaction
- 33. Setting Time Initial SettingTime Type – 1 3-6 min Type – 2 3-6 min Final Setting Time Type – 1 10 min Type – 2 15 min
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- 36. Advantages 1.Accurate & stabledimensionally. 2.They adhere well to dried surfaces of compound, resin and shellac bases 3.Inexpensive 4.Easy to manipulate 5.No requirement of separating medium Disadvantages 1.It cannot be used when a undercut exists. 2.Requires special tray 3.unpleasant (may cause burning sensation or irritation to the oral tissues). 4.Instruments are difficult to clean.
- 37. secondary or correctivewash impressions of edentulous arches. Temporary relining material and remodeling material. Uses
- 38. Modifications • Surgical Paste •Bite Registration Paste • Noneugenol Pastes • zinc oxide is reacted with carboxylic acid (Orthoethoxy benzoic acid)
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- 42. Rigid impression materials Impression compound Greenstick Zoe • Ada specification no • Filler • plasticizer • Dispensing • composition • Manipulation • Factors effecting setting time • Properties • Classification • Chemical reaction • Advantages • Disadvantages • Uses • modifications