Bonding

Question 1

what are the ideal properties of a bonding agent

Answer 1

strong bond to teeth, impermeable, durable, bond immediately

Question 2

what properties of enamel make it easy to bond to

Answer 2

inorganic, high surface energy, dry

Question 3

what is used for etching enamel

Answer 3

30% phosphoric acid

Question 4

how does phosphoric acid work for etching enamel

Answer 4

removes calcium hydroxyapatite, creates a porous surface,
characteristic etched pattern, allows the resin to flow in, increases critical surface energy, once resin flows in, can polymerise and cannot be pulled out

Question 5

what is the name of adhesion for enamel bonding

Answer 5

micro mechanical adhesion

Question 6

what makes bonding to dentine more difficult than enamel

Answer 6

it is more organic, has a dentinal fluid, this reduces the critical surface energy

Question 7

what is critical surface energy

Answer 7

the tension of a fluids ability to flow on a surface and stick on this surface - high, good flow and stick, low poor flow and not sticking, surface must be higher than the liquid

Question 8

what two ways can bonding to dentine occur

Answer 8

chemically or mechanically

Question 9

what is mechanical bonding to dentine

Answer 9

similar to that of enamel, creating porous surface for resin to flow in and micro mechanically lock in

Question 10

what is a surface wetting agent

Answer 10

an agent that increases the critical surface energy of a surface, to allow the flowability and adhesion of a liquid on the surface

Question 11

how does surface wetting agent work in dentine

Answer 11

it is a bifunctional molecule - one end is hydrophillic and one end is hydrophobic. dentine is a hydrophillic surface but the resin is hydrophobic. therefore, this agent can flow on to the dentine surface and polymerise to make the dentine hydrophobic

Question 12

what is the smear layer

Answer 12

the layer on dentine created during cavity preparation. normally full of bacteria and dentine - organic debris, interferes with adhesion

Question 13

what are the 3 components in dentine bonding

Answer 13

conditioner, primer and adhesion

Question 14

what is the conditioner used in dentine bonding

Answer 14

30% phosphoric acid, to remove calcium hydroxyapatite and increase porosity

Question 15

what is the primer used in dentine bonding

Answer 15

normally HEMA, this is a bifunctional molecule with a hydrophobic and hydrophillic end. It contains C=C for covalent bond with the next resin layer and increases the surface energy. main adhesion molecule

Question 16

what is the adhesion molecule used in dentine bonding

Answer 16

mix of Bis-GMA and HEMA. predominantly hydrophobic, creates a hybrid layer as it bonds to the dentine and the restorative material

Question 17

what is adhesion known as in dentine

Answer 17

molecular entanglement and micro mechanical retention

Question 18

what is the problem with moisture in bonding

Answer 18

too dry - collapse of collagen fibres, nothing to bond on to

too wet - resin cannot flow properly, surface energy low

Question 19

what is the problem with over etching

Answer 19

collagen collapse and the resin cannot penetrate as deep as the pores created

Question 20

what steps can be simplified in practice of dentine bonding

Answer 20

combine prime and adhesion - prime and bond, scotchbond, still uses total etch technique

Question 21

what is self-etchant technique

Answer 21

when one agent is used, containing etchant, primer and adhesion, reduces steps to reduce effects of poor moisture control