Dentin Bonding Agents II Flashcards
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describe the three step total etch
- etchant removes smear layer, exposing tubules in a funnel config –> increases H2O, which makes bonding more difficult; exposes intertubular and peritubular collagen
- primer - bifunctional molecules; external surface of collagen fibrils enveloped by it; reestablishes free energy to levels compatible with a more hydrophobic material
- mostly hydrophobic monomers suchas Bis-GMA; can also contain a small amount of hydrophilic monomers; copolymerises with primer molecules; penetrates and polymerizes into the interfibrillar spaces to serve as a structural back bone to hybrid layer
describe the one-bottle total etch
- etchant removes smear layer, exposing tubules in a funnel config –> increases H2O, which makes bonding more difficult; exposes intertubular and peritubular collagen; decreases surface energy
- primer + bonding agent
- penetrates into dentin tubules foring resin tags; first coat applied on etched dentin works as a primer –> increases surface free E of dentin; second coat acts as a bonding agent used in three step system –> fills spaces between the dense network of collagen fibres; not economical, and don’t need primer in enamel
describe teh two-bottle self etch
- produces best results
- etchant + primer (self-etching primer) –>does not remove smear layer; fixes it and exposes about 0.5-1 micrometer of intertub collagendue to its acidic;
- smear plug impregnated with acidic monomer, prepares pathway for penetration subsequently placed fluid resin into microchannels
- bonding agent - same type of bonding agent included in three step total etch system; resin tags form on resin penetration into microchannels of primer-impreg smear plug
describe all - in one self etch
- etches enamel
- incorporates smear layer on surface
- is aqueous and a phosphated monomer, so it demins and penetrates dentin simultaneously –> leaves ppt on hybrid layer
- forms thin layer of adhesive–>low bond strength; must use a few coats; incompatible with self-cure resins
describe the etch and rinse approach
etch and rinse –> allows water to come out of tubs and thus MMPs can attach collagen
describe the self-etch approach
doesn’t remove plug –> prevents water from getting in; ALSO you use a MILD acid; creates a resin-impreg smear plug
- use 10-MDP or 4-MET, or Phenyl-P to create ionic bond to phosphat/carboxylic group to Ca of hydroxy apatite
what is universal bonding?
products can be used in all situations (however, manufacturer may not define universal like we do)
- compatible with different etching techniques (self-, total-, selective-etch)
- compatible with dual- and self-cured mterials without the use of a separate activator
- can be used as a primer for silica-based, zirconia-based and metallic restos
what is selective etch?
etch with phos acid only on enamel; rinse; use universal primer everywhere
what are some consequences of failure of bonding to dental tissue?
- microleakage
- post-op pain
- loss of restorationn
why might failure of bonding occur?
- resin polymerization shrinkage
- polymerization stress
- degradation of collagen fibres
what is responsible for polymerization stress?
- type of resin
- intensity of the light
- water sorption
- cavity configuration
- filler content of the composite
- elastic modulus of the material
- curing characteristics
what is the instrumental technique in relation to polymerization stress?
place small amounts of composite first on the floor (cure), then on axial wall (cure), then the other (cure) and carve out anatomy – reduces stress
what are some of the bio-protective effects of bioactive dentin bonding agents
- control of bacteria
- strengthening of tooth substrate
- protection of interfacial deterioration (to prevent secondary caries or maintain integrity of the restorations)
give an example of a bioactive monomer?
- MDPB (quaternary ammonium methacrylates)
give an example of bio-promoting effects?
- remineralization
- promotion of tissue regen
