Curing / Etch / Dentine Bonding Agent Flashcards
What is light curing known as
Polymerisation process
What is gel point
Instant where material passes from liquid to solid
What causes stress
Setting up of bonding interface
Stress relieved up to what point
Gel point
After gel point, composite =
unyielding
Why 2mm curing depth
Minimise stress transferred
Why are fillers placed in composite
To decrease shrinkage
Materials in composite
Strontium glass
Barium glass
Borosilicate glass
Silica
Ceramic
Prepolymerised resin
Quarts
Etch
37% phosphoric acid
Ph of etch
0.2 strong acid
What occurs during etch
Decalcification
How long does decalcification take
5-8 seconds
What does etching do
Decalcifies portions of enamel rods
Mechanism of etch on tooth
Dissolves calcium salts
Inter prismatic and prism areas = exposed for interlocking tag formation with bonding resin
= mechanical bonding
Bond strength of etch
20mPa
Dentine bonding agents - mode of action
Need to change properties of dentine (smear layer) from hydrophilic to hydrophobic
Basic bonding to enamel/dentine =
Exchange process
Replacement of minerals by resin monomers
Micro mechanically interlocked in created porosity
Dentine hybrid layer
Hybridisation - infiltration of resin monomers into collagen fibrillar matrix of demineralised dentine then polymerisation
Creates a molecular level mix of adhesive polymers + hard tissues = hybrid layer
