Bonding to Teeth Flashcards Preview

BDS2 Dental Material Science > Bonding to Teeth > Flashcards

Flashcards in Bonding to Teeth Deck (13)
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1
Q

what are the ideal properties of a dental adhesive?

A
  • provide a high bond strength to tooth tissues
  • immediate high strength bond
  • durable bond
  • impermeable bond
  • easy to use
  • safe
2
Q

what does the etching of enamel provide?

A
  • increased surface energy of the enamel
  • therefor better wettability
  • allows resin to adapt better to roughened surface
3
Q

what acid is most commonly used to etch enamel?

A

30% phosphoric acid

4
Q

why is bonding to dentine more complicated that bonding to enamel?

A
  • dentine is WET (due to permeable tubules)
  • dentine has a low surface energy
  • dentine is hydrophilic whereas most bonding agents are hydrophobic
5
Q

what are the requirements of a dentine bonding agent?

A
  • ability to flow
  • potential for intimate contact with dentine surface
  • low viscosity
  • adhesion to substrate
6
Q

what is the effect of bonding agents to the surface of dentine?

A

dentine bonding agents INCREASE THE SURFACE AREA of dentine & allow composite to flow and stick to it

7
Q

what is the smear layer?

A

the smear layer is an adherent layer of organic debris that remains on the dentine surface after the preparation of the dentine during the restoration of a tooth

8
Q

what effect does etching have on the smear layer?

A

remove and/or modify the smear layer from dentine

9
Q

what is the function of phosphoric acid applied to dentine as a conditioner?

A
  • removes smear layer
  • opens dentinal tubules by removing smear plugs
  • decalcifies the uppermost layer of the dentine
10
Q

in terms of bonding to dentine, what is the primer and how does it function?

A
  • the primer is really the adhesive element
  • its a coupling agent
  • it contains a bifunctional molecule with a hydrophilic end to bond to dentine and a hydrophilic end to bond to resin
11
Q

what is a common coupling agent found in bonding primers? how does it work?

A

HEMA

- contains a C=C bone which opens and forms a strong covalent bone with the next resin layer

12
Q

in dentine bonding agents, how does the adhesive work?

A
  • predominately hydrophobic
  • penetrates the primed dentine which now has a hydrophobic surface
  • forms a micromechanical bond within the tubules and exposed dentinal collagen fibres
  • formed the HYBRID LAYER of collagen plus resin
13
Q

what can happen if the dentine is over etched?

A
  • collapse of the collagen fibres so no resin can penetrate

- too deep an etch and primer cannot penetrate full depth