Bonding Systems Flashcards
what are the properties of a dental adhesive?
high bond strength, immediate bond strength, durable bond, impermeable bond, easy to use, safe
what does the acid etch technique do to enamel?
roughens the surface of the enamel producing a characteristic etched pattern
what does the etched surface of enamel allow?
micromechanical interlocking of resin filling materials, increases surface energy of enamel surface by removing surface contaminants to allow better wettability
what does better wettability allow with enamel?
the resin to adapt better to the roughened enamel surface
what state must enamel be in to be etched?
dry
what acid is used for etch?
30% phosphoric acid
for enamel, what is applied after etch?
dentine bonding agent - BisGMA usually and then composite
what is the requirements of a dentine bonding agent?
ability to flow, potential for intimate contact with dentine surface, low viscosity, adhesion to substrate
how is dentine bonding acheived?
interlocking with dentine bonding agent and the dentine surface
if enamel is bonded at a mechanical level what is dentine bonded with?
chemical adhesion - molecular level
if the dentine is mineralised what type of bond occurs?
ionic
if the dentine is organic what bond occurs?
covalent
what is critical surface energy?
the surface tension of a liquid that will just spread on the surface of a solid
what must the respective surface energies for composite and dentine be?
low for composite and high for dentine
what do dentine bonding agents do in relation to critical surface energy?
increase the surface energy of dentine surface and allow composite to flow and stick to the surface
what is the smear layer?
adherent layer of organic debris that remains on the dentine surface after preparation of the dentine during the restoration of a tooth
what does a total etch bonding agent consist of?
dentine conditioner, primer and adhesive
what does dentine conditioner do?
remove smear layer, open dentinal tubules, decalcify top layer of dentin
what does the primer in DBA do
it is a coupling agent, bifunctional molecule with hydrophilic end attaching to dentine surface and hydrophobic end attaching to composite
what coupling agent is found in primers?
HEMA
what does adhesive contain?
HEMA and Bis-GMA, camphorquinone, filler particles
what does adhesive do?
forms a micromechanical bond within the tubules and exposed dentinal collagen fibres and forms the hybrid layer of collagen plus resin
what do all monomers in DBAs bond to?
calcium in hydroxyapatite
