Silorane composite resin simply discussed 2011

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dental Silorane composite resin 2 pages only 2011 simply discussed

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Silorane composite resin simply discussed 2011

  1. 1. * RBC = resin-based composite , RBCs = resin-based composites.Silorane resin-based compositeSilorane resin-based composite ( silorane RBC* ): good biocombatibility and low mutagenic potential( in comparison with oxirane RBC )Note: silorane resin = siloxane & oxirane .Oxirane : Cationic ring opening addition polymerization reaction ( while other methacrylate RBCs arefree radical addition polymerization reaction ).Low polymerization shrinkage ( less than 1% shrinkage, while other composites more than1.5% shrinkage )Less microleakage and better marginal integrity.Less polymerization stress.Siloxane : Increased hydrophobicityLess water sorption ( water sorption may result in hydrolytic degradation andfiller-matrix debonding ).Less absorption to dyes and less sensitive towards exogenic staining( about 50% less than other composites ).Less bacterial adhesion ( about 50% less than other composites ).Less solubility.Initiating system : Combines between ( balance between )High polymerization reactivity ( better than oxirane RBC ).( note: a reactive material develops its strength directly after light cure )Highest ambient light stability ( 10 min , while other composites wereless than 2 min ).( this allows the dentist to place the composite restoration underfull operatory light )Note: The electron donor decomposes the iodonium salt to an acidic cation , which opens the oxirane ring , andstarts the ring opening polymerization reaction.A critical mass of cations has to be formed to start the polymerization reaction. This is the reason for thehighest ambient light stability. ( ambient = surrounding ) , ( ambient light = operatory light )( camphorquinone,iodonium salt,electron donor )
  2. 2. * RBC = resin-based composite , RBCs = resin-based composites.Advantages of silorane RBC :1 , 2 : Low polymerization shrinkage and stress ( less than 1% polymerization shrinkage, while othercomposites more than 1.5% polymerization shrinkage ).3 : Less microleakage and better marginal integrity.4 , 5 : Less water sorption and solubility.6 : Less absorption to dyes and less sensitive towards exogenic staining ( about 50% less than othercomposites ).7 : Less bacterial adhesion ( about 50% less than other composites ).8 : Highest ambient light stability ( 10 min , while other composites were less than 2 min ).Note : Ambient = surrounding.Ambient light = operatory light.( this allows the dentist to place the composite restoration under full operatory light )9 : Good biocombatibility and low mutagenic potential ( in comparison with oxirane RBC ).What is the cause of polymerization shrinkage ?The resin molecules move toward each other to form chemical bond polymerization shrinkage.Why cationic ring-opening addition polymerization reaction resuls in lowerpolymerization shrinkage than free radical addition polymerization reaction ?Because ring opening (opening the ring) gains space and compensate shrinkage which occurs in thesubsequent step ( when the resin molecules move toward each other to form chemical bond ).How can we reduce polymerization stress ?Reducing polymerization shrinkage ( from seminar ), reducing stiffness (elastic modulus),reducing C-factor, incremental placement, curing technique and polymerization speed (e.g soft-startto allow for sress relaxation).

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