modified acrylics dental material


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modified acrylics dental material

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modified acrylics dental material

  1. 1. Modified Heat-cured Acrylics 1. Microwavable acrylic 2. Rapid-cured acrylic 3. High impact strength acrylic 4. Fiber-reinforced acrylic
  2. 2. Rapid-cured acrylic  An altered initiator that allows denture base processing in boiling water for only 20 min. Advantages  Rapid curing with minimal porosity Disadvantages  High % of residual monomer (3-7 times > Conv. HCA)  Lower mechanical properties  Porosity of bases ≥ 6mm thick
  3. 3. High impact acrylic  Powder is a graft copolymer of PMMA - butadiene rubber  2 formats of polymer beads are exist  No cross-linking is added to the composition Is better than Because it produces better dough characteristics Rubber Acrylic Rubber Acrylic
  4. 4. Advantages  High impact strength  Low crazing rates  Low residual monomer contents  Good attachment to art. Teeth and good fit Disadvantages  Expensive  Reduced stiffness High impact acrylic
  5. 5. Fiber and metal- reinforced acrylic  Certain fibers (Carbon, glass, Kevlar, Polyethylene) and metal fillers (Zerconia and alumina) are incorporated in acrylic powder Drawbacks  Carbon fibers cause black discoloration  Glass fibers are irritating and could injure soft tissues  Kevlar fibers complicate the packing process and gives straw color  Polyethylene fibers is promising  Adding metal fillers ↓ poly. Shrinkage but deteriorates the properties
  6. 6. Chemically-cured Acrylics  A chemical compound ( 3ry amine Activator) is added to the monomer composition to activate the initiator  An activator paste (P-toluine sulphonic acid) could be added to the regular acrylic to activate the polymerization at room temperature
  7. 7. Characters of the chemically-cured acrylic  Polymer beads have lower mol. wt.  Liquid contains chemical activator (3ry amine) to start the polymerization at room temp.  The material provides; 1. lower degree of polymerization 2. Lower mechanical properties 3. Higher % of residual monomer 4. Higher rate of porosity 5. Higher rate of water sorption 6. Lower color stability 7. No thermal shrinkage 8. Oversized dentures (+ 0.3-0.4%)
  8. 8. Characters of the chemically-cured acrylic  Practicability 1. Short processing time (10-15 min) 2. Complete polymerization occurs at room temp in 3 hrs 3. Both compression molding or fluid resin techniques could be used to fabricate denture bases Applications: - Denture base (temp &permanent) - Repair of broken dentures - Special trays
  9. 9. Fluid resin technique
  10. 10. Light- cured Acrylics The BVL is used to activate the photo-sensitive initiator named Comphroquinon The material is a composite structure Usually present as sheets or robs in light-proof pouches
  11. 11. Characters of the light-cured acrylic Composition: Composite Paste made of  Matrix of UDMA and PMMA  Microfine silica fillers  Organic fillers (Prepolymerized polymer beads)  Photoinitiator The material provides; 1. No MMA monomer is present (no allergy) 2. Lower physical and mechanical properties 3. Lower rate of polymerization shrinkage 4. Better fit
  12. 12. Applications  Denture base  Repair of broken prostheses  Special trays Denture construction  No flasking is required  Adaptation of sheet material over the cast to form the denture base  light curing for 5 min  Artificial teeth are then seat over the rob material  light curing for another 5 min Characters of the light-cured acrylic