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impression compound.pptx

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impression compound.pptx

  1. 1. IMPRESSION MATERIALS PREPARED BY: DR MANISH KATYAYAN (M.D.S.) ASSISTANT PROFESSOR DEPT. OF PROSTHODONTIA G.D.C.H AHMEDABAD
  2. 2. INTRODUCTION  An impression, in general terms, is a mark produced on a surface by pressure.  The word “impression” is derived from the Latin word impression.
  3. 3. DEFINITION  Impression Material – Any substance or combination of substances used for making an impression or negative reproduction. (GPT-2001).  Impression- A negative likeness or copy in reverse of the surface of an object, an imprint of teeth & adjacent structures for use in dentistry.(GPT-2001).
  4. 4. CLASSIFICATION Impression Materials Elastic Inelastic Hydrocolloid Rubbers -Impression compound Agar Alginate -Impression waxes - Impression plasters Mercaptan Polyether Silicones -ZOE Condensation Addition Lead peroxide Clean
  5. 5. Other ways to classify :- 1. By their generic chemical name:- eg. One may refer to silicone materials or ZOE materials. 2. According to the manner in which they harden:- Chemical reaction Temperature change (irreversible) (reversible) - Plaster of Paris Thermoplastic Non Thermoplastic - Zinc oxide Eugenol - Impression -Agar - Alginate compound - Non aqueous elastomers - Waxes
  6. 6. 3. According to the uses of materials in dentistry:- a) Materials used for obtaining impressions in dentulous mouth- - Alginate - Agar can also be used for edentulous - Non aqueous elastomers impressions b) Materials used for obtaining impressions of edentulous mouth- - Impression compound - Impression plaster - Zinc oxide Eugenol -Wax
  7. 7. 4. According to the viscosity or the tissue displacement:- Mucostatic Mucocompressive Impression plaster Agar Alginate Impression compound 5. According to the ability of the set material to be withdrawn from undercuts:- - Elastic - Inelastic
  8. 8. IMPRESSION COMPOUND
  9. 9. TYPE  Rigid  Reversible  Sets by physical change
  10. 10. CLASSIFICATION  TYPE 1- impression compound  TYPE 2- tray compound SUPPLIED AS cakes, sheets, sticks – in a variety of colours
  11. 11. USES FORTYPE 1(impression compound)-  For making primary or preliminary impression of edentulous jaws during denture fabrication.  For peripheral tracing or border moulding  For individual tooth impression FORTYPE 2( tray compound)-  To prepare a tray for making the secondary impression, thus acting as special tray  To check undercuts during inlay preparation.
  12. 12. COMPOSITION COMPOSITION INGREDIENTS PERCENTAGE ROLE Thermoplastic materials Natural resins, synthetic resins, waxes like carnauba wax 70 It is the main ingredient which forms the matrix. Gives thermoplastic properties Have high flow and low strength Plasticizers Shellac, stearic acid,gutta percha 5 Improves plasticity and workability Has high flow Fillers French chalk, talc 25 Increases viscosity at higher temperature Increases rigidity at mouth temperature Increases strength Colouring agents
  13. 13. STEPS OF MANIPULATION 1. Softening- the impression compound is softened in a thermostatically controlled water bath at a temperature of 55-60 C. 2. Kneading-after the compound is removed from the water bath it is usually kneaded with fingers to obtain uniform plasticity throughout the mass, 3. Loading-the softened compound is loaded into the stock metal tray. 4. Preforming-impression compound is indented with fingers to simulate the ridge impression. 5. Glazing-after preforming the impression tray is quickly passed over the flame to increase the flow of the surface layer to have fine tissue details.
  14. 14. 6. Tempering- material is tempered into the water bath before placing in the patient’s mouth.The temperature of the compound should be 45 C when placed in the mouth. 7. Placement-proper placement in the patients mouth. 8. Muscle movement- muscle trimming is done 9. Cooling-the impression is allowed to cool completely in the patient’s mouth. 10.Withdrawal and washing the impression. 11. Inspection of tissue details.
  15. 15. PROPERTIES 1.FUSION TEMPERATURE  When the impression copmound is kept in hot water the material starts softening at temperature of 39 C.  The temperature at which the material completely softens and looses its brittleness is known as fusion temperature.  It is a range and not a fixed temperature.  Above 43.5 C, the material softens and flows easily to form a plastic mass.  The impression should be made above this temperature.  Thus for impression compound the range for fusion temperature is 39-43.5C.
  16. 16. 2.THERMAL CONDUCTIVITY  It is a poor conductor of heat i.e the thermal conductivity is very low  Hence the material should be kneaded well to soften it completely before loading it on the tray and placing it in the patients mouth.  Also it should be allowed to cool completely before removing it from the patients mouth otherwise serious distortion may occur in the impression.
  17. 17. 3. DIMENSIONAL STABILITY  Due to the release of strains, some warpage or distortion of the impression may occur.  Thus to avoid such distortion- - the impression should be allowed to cool completely before removing it from the mouth -construct the die or the cast as soon as possible after the impression is taken- at least within an hour.
  18. 18. DISINFECTION  2% glutaraldehyde can be used to disinfect the impression.  The impressions should be immersed in this solution, rinsed and poured immediately.  Iodophors, chlorine compounds and phenolic spray can also be used.
  19. 19. ADVANTAGES  Can be re-used.  Inaccurate portions can be remade without repeating the entire impression  Has sufficient body to support itself as a tray and does not collapse from the peripheral portions.
  20. 20. DISADVANTAGES  Highly viscous hence tissue detail recorded is not that accurate.  Compresses the soft tissue while taking the impression.  Poor dimensional stability resulting in distortion.  Difficult to remove in deep undercut areas.  Usually the impression is over extended.

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