Composite

A hard, tooth-coloured restorative material

Composition
Organic Resin Matrix + Inorganic Filler Particles

Resin Matrix (ORGANIC)

• Bis-GMA (bisphenol-A-glycidyl methacrylate)
• UDMA (urethane dimethacrylate)
• TEGDMA (triethylene glycol dimethacrylate)

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Classifications

• According to filler size
  1. Macrofillers 10-100μm
  2. Midifillers 1-10μm
  3. Minifillers 0.1-1μm
  4. Microfillers 0.01-0.1μm (these fine particles give better polishing + aesthetics)
  5. Nanofillers 0.001-0.01μm (these fine particles give better polishing + aesthetics)

• Hybrid: composites with a mixed range of particle sizes, also called universal composites.
  • 0.04-3μm filler size
  • Particle size range defines the type of hybrid

• Flowable Composites
  • Reduced viscosity/flow easily
  • Low volume of filler particles
  • Unsuitable for deep restorations and load-bearing restorations
  • Used for lining cavities + class V (due to flexible properties)

• Packable composites ‘bulk-fill’
  • High viscosity
  • High volume of filler particles, low wear rate
  • Decreased polymerisation shrinkage
  • Increased rigidity

• Compomers (Composite-glassionomers)
  • 0.2-10μm
  • modified resin composite with an ion-leachable glass filler

• Ormocers (ORganically MOdified CERamics)
  • Inorganic+Organic preshaped polymer network
  • Low shrinkage
  • polysiloxane filler particles
  • High biocompatibility
  • Resistant to loadbearing
  • Aesthetic

• Siloranes (Siloxanes + Oxirns)
  • Low shrinkage
  • Hydrophobic properties – reduces adhesion of S. Mutans
  • Quartz particles + radio-opaque Fl^–
  • Ideal for posterior teeth

• Homogenous: filler particles within an uncured matrix
• Heterogenous: composites that contain a precured matrix or an unusual filler

Technique

• Select shade
• Rubber Dam/Isolation
• Prepare cavity
• Acid Etch (30-40% Phosphoric acid)
  • 30s enamel or 15s dentine
• Rinse
• Dry ( do not overdry dentine, to prevent collapsing the collagen network)
  • Look for frosted appearance on enamel
• Apply bond + primer and air dry 10s
• Light cure 20s (or according to manufacturers instructions)
• Layer and cure composite incrementally
  • 1-2mm layers
  • light cure 45s (or according to manufacturers instructions)
• Glycerin gel can be used to prevent oxygen inhibiting curing
• Finish and polish

Configuration Factor (C-factor)

• the ratio of internal walls vs external surfaces in an adhesive restoration (bound/unbound surfaces) – correlates with
  • Class I – 5:1
  • Class II – 4:2
  • Class III – 3:3
  • Class IV – 2:4
  • Class V – 1:5
• Curing results in composite becoming its solid state – this is called polymerization.
• During polymerization the composite bonds to the tooth surface, this in turn creates ‘competing forces’ and this has consequences on the treatment outcome
• The likelihood of these consequences correlate with the c-factor

Consequences

• Polymerization shrinkage which causes microleakages/secondary caries
• Inadequate proximal contact
• Stress cracks/craze/sensitivity
• Deformation of tooth cusps/dentinal tubules
• Bond failure

Reducing consequences

• Incremental layering/thin layering of composite
• Soft-start polymerization/ low-intensity light curing
• Appropriate use of flowable composites; low stress but high shrinkage
• Highly filled composites have larger polymerization stress but lower shrinkage