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Dental Material Science > Bonding > Flashcards

Flashcards in Bonding Deck (21)
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1
Q

what are the ideal properties of a bonding agent

A

strong bond to teeth, impermeable, durable, bond immediately

2
Q

what properties of enamel make it easy to bond to

A

inorganic, high surface energy, dry

3
Q

what is used for etching enamel

A

30% phosphoric acid

4
Q

how does phosphoric acid work for etching enamel

A

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

5
Q

what is the name of adhesion for enamel bonding

A

micro mechanical adhesion

6
Q

what makes bonding to dentine more difficult than enamel

A

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

7
Q

what is critical surface energy

A

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

8
Q

what two ways can bonding to dentine occur

A

chemically or mechanically

9
Q

what is mechanical bonding to dentine

A

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

10
Q

what is a surface wetting agent

A

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

11
Q

how does surface wetting agent work in dentine

A

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

12
Q

what is the smear layer

A

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

13
Q

what are the 3 components in dentine bonding

A

conditioner, primer and adhesion

14
Q

what is the conditioner used in dentine bonding

A

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

15
Q

what is the primer used in dentine bonding

A

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

16
Q

what is the adhesion molecule used in dentine bonding

A

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

17
Q

what is adhesion known as in dentine

A

molecular entanglement and micro mechanical retention

18
Q

what is the problem with moisture in bonding

A

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

too wet - resin cannot flow properly, surface energy low

19
Q

what is the problem with over etching

A

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

20
Q

what steps can be simplified in practice of dentine bonding

A

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

21
Q

what is self-etchant technique

A

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