Bonding to Dentine/Enamel

Question 1

bonding to enamel is

Answer 1

easy
due to structure
highly mineralised 95% inorganic

Question 2

technique to bond to enamel

Answer 2

acid etch
roughens surfaces, interlocking of resin, increase surface energy, better wettability, adapts better
must be dry, moisture prevents flow of resin
30-50% aqueous solution of phosphoric acid

Question 3

bonding to dentine is

Answer 3

difficult
20% organic [collagen] 70% inorganic [hydroxyapatite] 10% [water]
fluid pumps from pulp to dentine floor, wet surface
varies in mineralisation
smear layer

Question 4

requirements of dentine bonding agent

Answer 4

flowability, intimate contact with dentine surface, low viscosity, adhesion to substrate

Question 5

smear layer

Answer 5

adherent layer of organic debris that remains on dentine surface after preparation of dentine during restoration
interferes with adhesion, removed by acid conditioning to dissolve or solubilise plugs
EXPOSE TUBULES TO CREATE PORES FOR RESIN

Question 6

critical surface energy

Answer 6

surface tension of a liquid that will just spread on a surface of a solid
liquid must be lower than surface being placed on for it to flow and stick
DBAs increase surface energy to allow composite to flow and stick

Question 7

adhesion through molecular entanglement

Answer 7

adhesion absorbed on the surface due to good wtting of dentine and surface energies
molecular entanglement = high bond strength
involvement of saliva/dentinal tubules = weak bonds

Question 8

total etch components

Answer 8

conditioner - acid 35% phosphoric acid
- removes smear layer, opens dentinal tubules by remocing smear plugs, decalcifies dentine upper
primer - adhesive element, coupling agent
- spacer group to allow flexible bonding
bond adhesive - resins that penetrate into dentine surface attaching to primers
- froms hydbrid layer
- contains comphorquinone to allow LIGHT CURE

Question 9

problems with total etch

Answer 9

overetching - collapse of collagen fibres so not resin penetrate, depth of cure too deep, leabing unsupported collagen
moisture dependent - too dry means surface collapses, too wet means primer diluted so decreased strength

Question 10

self etching primer and seperative adhesive

Answer 10

doesnt remove smear layer, incorportes in bonding matrix, not washed off, bond isnt as good

Question 11

fundamentals of bonding

Answer 11

mineral exchange, minerals removed from dental hard tissues rpelaced by resin, mechanically interlock in porosities [molecular entanglement]
bonding agents are wetting agents