Composite
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What are the components of composite?
Glass filler particles - quartz Resin monomer (most common bis-GMA) Camphorquinone - light-activator Lowe weight di-methacrylates Silane coupling agent
What does silane coupling agent do within composite?
Acts as an intermediary to bond inorganic material to organic e.g. glass and resin Increases strength
What is the etch most commonly used?
37% phosphoric acid etch
What does acid etching do to a tooth?
• Increases the surface roughness - creates spaces within enamel to allow for MICROMECHANICAL ADHESION • Removes contaminants from surface - removes the SMEAR LAYER • Unblocks dentinal tubules • De-mineralises dentine surface, exposing collagen network.
What does DBA do?
Increases surface wettability - facilitates bonding between wet, organic tooth material and dry composite.
What is the HYBRID layer?
Formed when the composite resin penetrates into the dentinal tubules and forms a tight bond.
What is the SMEAR layer?
Layer of organic debris remaining on the surface of dentine after tooth has been cavity prepped.
What is a disadvantage to the setting reaction of composite?
Polymerisation setting reaction - some free monomer may be left after set. Some people can be allergic to monomer - may not be biocompatible if toxic to pt.
Advantages of composite?
Strong Good bond strength to tooth Good aesthetics Low setting shrinkage Low thermal conductivity Radio-opaque Rigid
Disadvantages of composite?
High thermal expansion co-efficient - not similar to tooth. Need moisture control to bond.
What is composite bond strength?
40MPa