dental cements, composite, impression

Question 1

the peaks and valleys of dental and resto surfaces can be extremely vulnerable to what?

Answer 1

bacteria and caries

Question 2

function of cements

Answer 2

• seal margins

- retain crowns

Question 3

wetting

Answer 3

describes the ability for a liquid to flow easily over the entire surface and adhere to the solid

Question 4

what do you need for good wetting

Answer 4

cement/adhesive = low surface energy
substrate = high surface energy

Question 5

contact angle should be high or low for good wetting?

Answer 5

low

Question 6

what happens if cohesion is stronger than the surface energy of impression material

Answer 6

bubbles

Question 7

luting cement should have ____ solubility

Answer 7

low solubility (because exposed to oral fluids and margins can disintegrate)

Question 8

objectives of cementation

Answer 8

1) retain resto in place

2) maintain integrity of tooth

Question 9

cementing

Answer 9

joining of 2 materials

Question 10

luting

Answer 10

filler material between 2 surfaces (WITHOUT adhesive)

Question 11

bonding

Answer 11

material that forms a chemical bond between 2 surfaces (WITH adhesion)

Question 12

what 4 dental cements are used in practice today?

Answer 12

• glass ionomer cement
• resin-modified glass ionomers
• resin cements
• mineral trioxide aggregate

Question 13

reaction in GIC

Answer 13

fluoroaluminosilicate glass powder + polyacrylic acid

Question 14

steps for reaction of GIC

Answer 14

1) acid dissolves glass and releases ions
2) PAA chains crosslinked by Ca ions
3) Ca replaced by Al ions
4) undissolved glass is sheathed by silica-rich gel

Question 15

slow setting problem with polycarboxylate acid reacting slowly can be solved with what?

Answer 15

tartaric acid

Question 16

what advantages does tartaric acid have?

Answer 16

• forms stronger complexes with Al ions

- reacts preferentially with Ca ions

Question 17

rapid release of F ion from

Answer 17

matrix

Question 18

slow release of F ion from

Answer 18

particle

Question 19

release of F from glass ionomer

Answer 19

low intraoral F concentration

Question 20

recharge of F into glass ionomer

Answer 20

high intraoral F concentration

Question 21

how does glass ionomer chemically bind to dentin

Answer 21

chelation of carboxyl groups of PAA with Ca in hydroxyapetite

Question 22

Resin modifies glass ionomers (RMGI)

Answer 22

• acid-base reaction
• resin polymerization
• add hydrophile (HEMA) to PAA (allows PAA chains to connect via resin matrix)

Question 23

what does acid etching do

Answer 23

dissolves the smear layer that forms after cutting/grinding dental surface
-exposes enamel crystal prisms and dentin collagen fibrils (allows penetration of resin for micro-mechanical interlocking)

Question 24

what layer of the hybrid layer does adhesive resin enter

Answer 24

primed demineralized dentin -enters “resin tags”

Question 25

most resin cements require

Answer 25

adhesive monomer (dentin bonding agent)