Waxes (thermoplstics) in dentistry

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an over view of waxes and its properties used in dentistry

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Waxes (thermoplstics) in dentistry

  1. 1. Waxes (Thermoplstics) in Dentistry 1 D R M U M TA Z U L I S L A M B.Sc. BDS. C. Implant. C. Ortho. 12/5/2013
  2. 2. Waxes 2  Waxes are thermoplastic materials  Soft on heating hard on cooling  Solid at room temperature  Melt without decomposition  Form mobile liquids  Poor mechanical properties  Used to form patterns (wax pattern) 12/5/2013
  3. 3. Patterns 3  Direct wax pattern  Indirect wax pattern  lost-wax technique 12/5/2013
  4. 4. Direct 4 12/5/2013
  5. 5. Indirect 5 12/5/2013
  6. 6. Types used in dentistry 6  Fixing denture teeth for displaying (carding wax)  Boxing in dentures before making the model (boxing-in      wax) Temporary joining two broken pieces (sticky wax) For taking impression (impression waxes) To control hemeostasis (bone wax) In endodontics (gutta percha) In orthodontics (orthowax) 12/5/2013
  7. 7. Waxes 7 12/5/2013
  8. 8. Processing wax 8 12/5/2013
  9. 9. Full range of processing waxes 9 12/5/2013
  10. 10. Modeling wax 10 12/5/2013
  11. 11. Modeling wax 11 12/5/2013
  12. 12. Wax rims 12 12/5/2013
  13. 13. Wax bite blocks 13 12/5/2013
  14. 14. Wax bite 14 12/5/2013
  15. 15. Wax bite 15 12/5/2013
  16. 16. Base Plate Wax 16 12/5/2013
  17. 17. Sticky wax 17 12/5/2013
  18. 18. Bone wax 18 12/5/2013
  19. 19. Ortho wax 19 12/5/2013
  20. 20. Ortho wax 20 12/5/2013
  21. 21. Requirements of a pattern 21  Copy exact size Shape & Contour  Dimensionally stable after formation of pattern  Easily be removed after mould formation  For indirect use its melting point should be above room temperature  For direct use it should set at mouth temperature  Molding temperature 12/5/2013
  22. 22. Sources 22  Mineral  Animal  Vegetable 12/5/2013
  23. 23. Mineral 23  Parrafin wax (straight chain) brittle  Microcrystalline wax( branched) elastic  Petrolium byproducts  Hydrocarbons 12/5/2013
  24. 24. Softening and Melting Temperature 24  Softens at 37 to 55 ͦ C  Parrafin wax melts at 44 to 70 ͦ C  Microcrystalline waxes melt at 65 to 90 ͦ C 12/5/2013
  25. 25. Animal 25  Bees wax  Honey combs  Partially crystalline natural polyesters  It can flow under stress just below the melting point  Very flow able 12/5/2013
  26. 26. Vegetable 26  Derived from trees and plants  Carnauba wax (Brazil wax or Palm wax)  Candelilla wax 12/5/2013
  27. 27. Properties 27  Thermal  Mechanical 12/5/2013
  28. 28. Thermal 28  Melting point  Solid-solid transition temperature (lower than melting point) brittle state changes into a mouldable and softer material  Softening temperature just above the mouth temperature  Poor thermal conductor (must be kept above SST for thorough softnening)  High coefficient of thermal expansion 12/5/2013
  29. 29. Mechanical 29  Flow more during moulding and no flow at mouth or     room temperature prevents distortion Brittleness inherent property can be controlled desired in inlay wax Toughness more desirable in wax denture base Internal stress Dimentional changes 12/5/2013
  30. 30. Methods of Softening 30  water bath  Infra-red lamp 250 watts  Bunsen burner  It should not touch the flame  Glossy (shiny) appearance indicates melting outer surface  In water uniform but leaching of constiuents occours  Water incorporation also alters its composition and properties 12/5/2013
  31. 31. Ideal method for softening 31  Wax annealer  Thermostatically controlled oven which keeps the wax at a constant temperature  just above the softening point  Ready for use  The annealer is most useful for inlay waxes 12/5/2013
  32. 32. Applications 32  Processing waxes  Denture modeling wax  Wax rim  Mounting artificial teeth on that rim  Three types  Type 1 soft  Type 2 hard  Type 3 extra hard 12/5/2013
  33. 33. Application (contd,) 33  Type 1 material  Hard at room temperature but soft at mouth temperature  Building contours and veneers in the laboratory  The type 2 material  For pattern production in temperate climate  Type 3 material  For use in warmer climates  Modelling waxes consist mainly of mixtures of paraffin wax and beeswax and have melting points in the range 49–58ºC 12/5/2013
  34. 34. Dimentional Stability 34  High values of coefficient of thermal expansion  Manner in which the materials are used (softening with heat and cooling) suggests that a significant dimensional change can occur  An upper limit of 0.8% expansion on heating from 25ºC to 40ºC is allowed in the ISO specification 12/5/2013
  35. 35. Pre-formed Polymeric Components 35  An alternative to waxes for modelling the metal components of partial dentures  Available in sheets 12/5/2013
  36. 36. Temporary Denture Bases 36  Constructed from wax and used during denture construction are prone to distortions unless great care is taken  For this reason alternative materials/techniques are sometimes used  Shellac a wax-like resin which is more stable at mouth temperature has been used for construction of the temporary denture base 12/5/2013
  37. 37. Shellac 37  Natural beetle exudate which has a considerably higher softening temperature than ordinary modelling wax  Care must be taken to ensure thorough softening prior to moulding otherwise considerable stresses are introduced which eventually lead to distortion  The wax rim is then built on top of this more stable base 12/5/2013
  38. 38. Shellac 38 12/5/2013
  39. 39. Inlay waxes 39  Inlays or cast posts etc produced by patterns  Direct  Indirect  Two types of inlay casting waxes  Type 1 soft indirect  Type 2 hard direct (may be used indirectly)  Presentation is in the form of cones, sticks and cakes 12/5/2013
  40. 40. Requirements 40  Should soften just above mouth temperature  Magnitude of thermal contraction and internal stresses should be minimum  Softening temperature must be tolerated without pain by the patient  Thermal contraction occurring on removal of the direct pattern material from the mouth is 0.1–0.5%  Investing the pattern as soon as possible is required 12/5/2013
  41. 41. Requirements 41  Hard at mouth temperature  On removal from the cavity fractures not to flow  This enables the undercuts to be located and removed  Good colour contrast with enamel  Easy to carve without flaking 12/5/2013
  42. 42. Pattern of Post 42  The post channel is usually prepared using a proprietary system and a pre-formed pattern for the post is installed into the canal  The core is then built up in wax by melting the wax on an instrument and carrying the molten wax into the tooth 12/5/2013
  43. 43. Indirect Patterns 43  Soft type  Some what same like direct  Softens at lower temperature than direct  No flow at room temperature  Thermal contraction is much lower as lower softening temperature  A distinct advantage of the indirect technique 12/5/2013
  44. 44. Thank you 44 12/5/2013

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