Dental Materials Pt. 2(12-26)

Question 1

hydrophobic surface properties

Answer 1

composite put into tooth

Question 2

hydrophilic surface properties

Answer 2

tooth surface

Question 3

composite and tooth being opposite of each other (hydrophobic vs philic) adds…

Answer 3

strength to the bond

Question 4

the angle a force by the jaw is applied to a tooth or composite effected the amount of force

Answer 4

the contact angle

Question 5

different angles of the jaw can have

Answer 5

different forces

Question 6

molecules can have both hydrophobic

Answer 6

and hydrophilic components (adhesives- bind to composite and tooth so compatible with both surfaces)

Question 7

types of corrosion in metals

Answer 7

Galvanic corrosion
structure selective corrosion
crevice corrosion
stress corrosion

Question 8

degredation in ceramics caused by

Answer 8

hydrolysis

Question 9

hydolysis in ceramics

Answer 9

dissolution of oxides created by H-bonds (fluoride treatments dissolve ceramics)

Question 10

polymers degraded by

Answer 10

hydrolysis

Question 11

hydrolytic degredation in polymers caused by

Answer 11

water (absorb water and causes dimensional changes)
enzymes
bacteria

Question 12

degradation products are related to

Answer 12

toxicity (mercury and plastics absorbed by body over time and cause harm)

Question 13

Stress strain curve y axis

Answer 13

stress

Question 14

stress strain curve x axis

Answer 14

strain

Question 15

steep angle on stress strain curve

Answer 15

stiff and brittle, shatters with sharp forces

Question 16

food resembling steep angle

Answer 16

pretzel

Question 17

middle angle on stress strain curve

Answer 17

stiff and ductile, deforms then fails

Question 18

food resembling middle angle

Answer 18

tootsie roll

Question 19

low angle on stress strain curve

Answer 19

flexible and ductile, lots of manipulation before it breaks

Question 20

food resembling low angle

Answer 20

liquorish

Question 21

tendency to deform along an axis with opposing forces (stress and strain)

Answer 21

modulus

Question 22

before failure or fraction occurs

Answer 22

toughness

Question 23

before deformation occurs

Answer 23

resilience

Question 24

how does heat affect mechanical properties

Answer 24

decrease strength because material becomes pliable and easily manipulated

Question 25

creep

Answer 25

solid material moves slowly/deforms permanently under mechanical stress (long term)

Question 26

impressions want to be taken out____ to retain___

Answer 26

quickly to retain best impression without deformation

Question 27

the ability of a material containing a crack to resist further fracture

Answer 27

fracture toughness

Question 28

single cycle (force) overload such as biting on popcorn cornel leads to

Answer 28

cracks

Question 29

cyclic stresses are

Answer 29

slow cracks propogating over time (fatigue of teeth) caused by soft foods

Question 30

teeth are not completely rigid and can lead to

Answer 30

abfractions

Question 31

how the teeth articulate with each other creating an ideal environment for mastication

Answer 31

buccal lingual stability

Question 32

how do cavities lead to B-L instability?

Answer 32

taking out cavity removes tooth material and weakens structure, putting more stress on remaining tooth and causing cusp fractures

Question 33

in composite resins, resin helps

Answer 33

processing and handling

Question 34

in composite resins, filler helps

Answer 34

modulus and wear resistance

Question 35

in composite resins, the role of coupling agent

Answer 35

bonding between filler and matrix

Question 36

resin ______ viscosity and filler _____ viscosity, but decreases flowability

Answer 36

increases viscosity, increases viscosity (which ultimately improves mechanical properties)

Question 37

types of curing

Answer 37

chemical heat light

Question 38

what is corsslinking

Answer 38

the linking of polymers within resin which can alter density with number and degree of crosslinking

Question 39

crosslinking increases or decreases strength

Answer 39

increases

Question 40

cross linked groups need to be ______ for this process to be effective in increasing strength

Answer 40

bonded together

Question 41

smaller fillers are

Answer 41

better

Question 42

smaller fillers match

Answer 42

tooth structure and have better wear properties

Question 43

smaller fillers allow for better/worse polishing and finishing

Answer 43

better

Question 44

micron (fine) fillers

Answer 44

.5-3 um | loaded at 77-88wt%

Question 45

nano (microfine) fillers

Answer 45

.04-.2um tendency to aggregate 38% maximum loading percentage

Question 46

nano in polymer matrix

Answer 46

20-30um particles loading up to 50-60% reduces aggregation and no coupling agent

Question 47

these form very strong bonds between fillers and resin

Answer 47

coupling agents

Question 48

coupling agents add what groups and what do they bond to

Answer 48

add methacryalte groups that can bond with polymer chains to surface of filler

Question 49

Shrinkage

Answer 49

density change of monomers into polymers

Question 50

shrinkage is important for

Answer 50

direct compostite restorations and materials that require dimensional stability

Question 51

shrinkage can cause cracks that lead to

Answer 51

secondary caries

Question 52

Components of glass ionomer cements

Answer 52

acidic polymer (polyacid) basic class water modifiers (tartaric acid)

Question 53

glass ionomers are cured by

Answer 53

acid- base reaction

Question 54

reaction of poly acid and glass creates

Answer 54

salt bridges that form from poly acid to glass

Question 55

difference between composite bonds and glass ionomer bonds

Answer 55

composite has cross bridges between polymers and glass ionomer has salt bridges between poly acid and basicglass

Question 56

glass ionomers release

Answer 56

fluoride to help tooth strength once set

Question 57

difference between adhesives and composites

Answer 57

adhesives are 0-10% filler and composites are 70-80% filler

Question 58

adhesives are base on

Answer 58

composite resin chemistry

Question 59

hydrophilic modifiers promote

Answer 59

bonding

Question 60

enamel and dentin are hydrophilic/phobic

Answer 60

hydrophilic

Question 61

compsites are hydrophilic/hydrophobic

Answer 61

hydrophobic

Question 62

ahesive layers are hydrophibic/philic

Answer 62

both

Question 63

how do sealants differ from composites?

Answer 63

``` preventative material low viscosity (easy to flow/coat surface) bonding is mostly mechanical (etching) not for longevity ```

Question 64

oxygen inhibition layer in sealants interferes with

Answer 64

radical polymerization

Question 65

why is oxygen inhibition a problem?

Answer 65

surface is uncured and this is problem because sealants are so thin

Question 66

classes of impression materials

Answer 66

hydrocolloid and elastomers

Question 67

properties of hydrocolloid

Answer 67

alginate, irreversible, lacks some accuracy, sets via chemical and temperature

Question 68

properties of elastomers

Answer 68

higher tear strength, stable dimensions, rubber like polymer

Question 69

con of elastomers

Answer 69

expensive

Question 70

alginates are ___based

Answer 70

water based

Question 71

alginate is ___ crosslinked

Answer 71

calcium cross linked

Question 72

calcium cross linked is part of

Answer 72

initial reaction while material is still workable

Question 73

calcium cross links react with

Answer 73

sodium alginate to form gel

Question 74

advantages of alginate being water based

Answer 74

use water temp to manipulate setting time

Question 75

the colder the water

Answer 75

the slower the setting time

Question 76

advantages of alginate

Answer 76

cheap, easy, fast, tastes fine, hydrophilic, displaces blood and saliva

Question 77

disadvantages of alginate being water based

Answer 77

undergoes shrinkage or expansion with loss/gain of water

Question 78

syneresis

Answer 78

loss of water to surroundings

Question 79

imbibition

Answer 79

gain water from surroundings

Question 80

other disadvantages of alginate

Answer 80

limited detail, single pour only, work quickly, low dimensional stability

Question 81

what determines time alginate material will set

Answer 81

sodium phosphate levels (water temps)

Question 82

heating

Answer 82

expand

Question 83

cooling

Answer 83

contract

Question 84

fillers reduce

Answer 84

water soprtion

Question 85

water sorption promotes

Answer 85

hydrolysis

Question 86

water sorption degrades

Answer 86

matrix and matrix filler bonding

Question 87

smear layer is removed by

Answer 87

etching

Question 88

spherical

Answer 88

molten alloy blown through nozzle (wetted with less mercury than lathe cut

Question 89

expansion vs contraction steps

Answer 89

- initial contraction when alloy is absorbing mercury - expansion from formation and growth of y1 and y2 - final absorption of mercury again causes contraction