Troubles of heating cd


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Troubles of heating cd for Dr mohammed Elkhodary

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Troubles of heating cd

  1. 1. Dr/ Mohamed Elkhodary Asso. Prof. of prosthodontic [email_address]
  2. 2. بالأمس .. yesterday و اليوم .. Today
  3. 3. العقل البشري <ul><li>عدد الخلايا 1000000000000 خلية </li></ul><ul><li>مجموع الوصلات 10000000 كيلومتر </li></ul>ماذا يعني ذلك ؟ !
  4. 4. استراحة
  5. 5. استراحة
  6. 6. Troubles of heating CD: Processing errors
  7. 8. 1-Porosity: <ul><li>a)Too rapid rise of temperature in the initial stage of curing </li></ul><ul><li>b)Thick denture bases heated too rapidly. </li></ul><ul><li>c)Lack of dough in the mold at the time of final closure. </li></ul><ul><li>d)Lack of adequate pressure during polymerization. </li></ul><ul><li>e)Packing the resin in a sticky rather than doughy stage. </li></ul>
  8. 9. 2-Tooth movements <ul><li>a) The use of plaster instead of stone in investing the trial denture . </li></ul><ul><li>b) Incomplete closure of the flask . </li></ul><ul><li>c) Excessive and rapid pressure during trial closure . </li></ul><ul><li>d) Over packing of the mold with resin material before final closure . </li></ul><ul><li>. </li></ul>
  9. 10. 3 . Denture base and teeth breakage during Deflasking <ul><li>a) Careless flasking( knife blade hit teeth when removing stone cap) . </li></ul><ul><li>b) Hammer used to tap denture out of the flask . </li></ul>
  10. 11. 4 . Fractured or cracked teeth : <ul><li>causes : </li></ul><ul><li>a) Improper Deflasking( use hammer) </li></ul><ul><li>b) Packing the dough in the rubbery stage the material too stiff . </li></ul><ul><li>c) Excessive and rapid application of pressure during trial packing . </li></ul><ul><li>d) Setting the teeth directly on the stone cast . </li></ul>
  11. 12. 5 . Crazing of acrylic resin base or acrylic teeth : <ul><li>crazing of resin consists of the formation of small cracks which may vary in size from microscopic dimension to the visible size it indicates beginning of fracture . </li></ul><ul><li>causes : </li></ul><ul><li>a) Stresses induced by the contraction of the resin around the tooth by rapid cooling . </li></ul><ul><li>b) The use of solvents to remove wax from the mold before packing . </li></ul><ul><li>C) Application of separating medium just before packing </li></ul>
  12. 13. 6 . Bleaching of acrylic resin <ul><li>causes : </li></ul><ul><li>a) Contamination of the acrylic resin with some acrylic solvents . </li></ul><ul><li>b) under cured acrylic resin due to incorrect time and temperature of curing . </li></ul><ul><li>c) incorporation of the tin foil substitute with the acrylic resin . </li></ul><ul><li>d) incorporation of the jelly like material of wet cellophane into the resin . </li></ul>
  13. 14. استراحة
  14. 15. استراحة
  15. 16. 7 . color streaks in the resin material: <ul><li>causes: </li></ul><ul><li>a) improper mixing of the monomer and polymer . </li></ul><ul><li>b) contamination of the resin mix with dirty hands or instrument . </li></ul><ul><li>c) adding resin material in layers during trial packing . </li></ul>
  16. 17. 8 . Sandy appearance of the resin material : <ul><li>Causes ; </li></ul><ul><li>a) Too much delay in curing after packing [ more than 12 hour ] . </li></ul><ul><li>b) Evaporation of the monomer liquid. </li></ul><ul><li>c) Insufficient monomer in the mix (packing of a dry mix) . </li></ul>
  17. 18. 9 . Stone adhere to the surface of the denture: <ul><li>Causes ; </li></ul><ul><li>a) Insufficient separating medium on the mold before packing . </li></ul><ul><li>b) The application of separating medium contaminated with stone . </li></ul><ul><li>c) Incomplete elimination of wax during washing out thus rendering separating medium ineffective . </li></ul>
  18. 19. 10 . Space between the teeth and resin base: <ul><li>Causes : </li></ul><ul><li>a) Delayed curing leaving the flask without curing for a long time . </li></ul><ul><li>b) The application of separating medium on the teeth </li></ul>