Adhesion/Acid etch/Dentine bonding agents Flashcards
adhesive materials give the potential to?
seal vulnerable pits and fissures
conserve tooth tissue
reduce and eliminate leakage
what are the 3 approaches to achieving adhesion?
micromechanical attachments
chemical adhesion to enamel and dentine
complex adhesion - wetting, penetration and formation of bound material of restorative substrate interference
example of micromechanical attachment products?
acid etch
resins
example of chemical adhesion to enamel/dentine products?
coupling agents
cements containing polyacids
example of complex adhesion products?
modern dentine bonding agents
a low contact angle gives?
good wetting
attraction between adhesve and adhered lowers what?
the surface tension of adhesive = so will flow into irregularities
acid etch for enamel margins developed by?
is the application of what?
Bounocore 1955
acid gel
acid etch of enamel margins is the selective decalcification of?
creates what?
enamel prisms
micromechanical tags into which bonding resin may flow
acid etch increases surface what?
surface roughness - microscopically
acid etch incrases enamel surface energy by?
removing surface contaminants
increases wetting
facilitates micromechanical retention
do not etch for too long or what will happen?
etch for how long to get effect?
too long - allows re precipitation of calcium and phosphate
10-60 seconds
wash to etch for how long?
60 seconds to remove debris
dry to allow what when etching?
to enable hydrophobic resin to penetrate and attach
why stick to same manufacturer?
avoid potential chemical compatibility problems
avoid light curing problems especially if using LED
what properties does an ideal dental adhesive have?
high bond strength to enamel and dentine an immediate and durable bond a reliable bond prevent bacterial ingress safe and simple to use
problems with dentine bonding?
dentine is hydrophilic and adhesives are hydrophobics
vital
consits of organic and inorganic material
covered by a smear layer
what are primers?
dentine conditioners
acids
alter surface appearance and characteristics of dentine
what are coupling agents?
primers
components that do the sticking
what are sealers?
flows into dentinal tubules
seals dentine with surface layer rich in methacrylates
ensures bonding to the resin in composite
dentine conditioners - examples?
maleic, oxalic, phosphoric and nitric acids
how do dentine conditioners work?
acid base reaction with hydroxyapatite
open dentinal tubules
demineralize surface dentine to a depth of 4 microns
how do primers work?
act as adhesives
bond hydrophobic composites to hydrophilic dentine
generally - M-R-X dissolved in volatile solvent
how does HEMA work?
bonds to hydroxyl of apatite and amino groups of the collagen
solvent enhances penetration by seeking and displacing water carrying the coupling agent with it
types of sealers?
resins
mix of BISGMA and HEMA
acid opening of tubules risks what?
nano leakage
- dentine etch is greater than resin can penetrate
- dentine microstructure disruption and failure
3 stage process of sealing
- application of etchant, washed off creating dentine demineralised layer
- application of primer
- application of sealer
2 stage process of sealing - approach one
1 - application of etchant - washed off creating dentine demineralised layer
2 - application of primer and sealer in single solution
2 stages of sealing - approach two
1 self etching primer
2 application of sealer in single solution
one stage sealing?
self etching primer and sealer applied as single solution
components supplied in two pouches and mixed before use
