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Composite Resins (Dispersed phase (filler) (Type of Fillers (Nanofillers…

- - - - Harder, denser and more resistance to wear
      - Reduces polymerization shrinkage, water sorption and coefficient of thermal expansion
        
        More fillers --> less monomers --> less contraction of composite
      - Improves translucency and handling
  - - - Increases hardness but hard to polish
    - - less hard than quartz
    - - Provides radioopacity
      - lots of problems
  - - - Pyrogenic silica --> makes resin very viscous
    - - Below range of wavelength of visible light
        
        Light can go through without being blocked --> increases rate of polymerization
      - Allow particles to fit into spaces to increase filler loading
      - THE BEST
  - - - Elastic modulus
      - Fracture strength
      - Fracture toughness
- - - - Photochemical initiators
        
        Past: UV light, benzoin alkyl ether
        
        Visible light -- camphorquinone and tertiary amine
      - Thermochemical Initiators
        
        Benzoyl peroxidase
        
        Results in free radicals to initiate polymerization
    - - hydroquinone
        
        removes free radicals to stop polymerization
        
        prevents premature polymerization to ensure adequate shelf life
    - - Interacts with initiator to produce free radicals
    - - UV light absorbers
        
        Reduces rate of composite discolouration
        
        Ensures long shelf life
      - Suitable colour pigments
        
        Colour stable and non toxic
        
        Use of iron, titanium and aluminium oxide
  - - - Colourless liquid
      - Very viscous
      - Undergoes high cross-linkages (polymerizes a lot, leaves little residual monomers)
      - Relatively low polymerization shrinkage
      - High molecular weight dimethacrylate
      - PROBLEMS: degrade, change colour and toxic
      - Advantages
        
        Acceptable compatibility
        
        Radiolucent
        
        Hardens rapidly under oral conditions
        
        Polymerization strongy inhibited by air
        
        Hydrophobic
    - - Larger molecule in size and chemical structure
      - Lower volatility
      - Lower polymerization shrinkage
      - More rapid hardening
      - Stronger and stiffer
- - - - Flowables (low viscocity)
        
        Reduced filler content
        
        Surfactants to enhance fluidity
        
        Enhanced adaptation
      - Packables (high viscosity)
        
        Modification of filler size distribution
        
        Adding other types of particles such as fibres
        
        To provide an amalgam -like material
- - - - Compomers
        
        Composite Resin