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dental materials clinical practice > mix > Flashcards

mix Flashcards

1
Q

what are the 2 types of amalgam?

A

conventional - 6% copper

high copper - 30% copper

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2
Q

what are the different forms of amalgam?

A

lathe cut
spherical
admixed

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3
Q

what compound takes place in the setting reaction of amalgam?

A

Ag3Sn

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4
Q

what chemical strengthens amalgam?

A

copper

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5
Q

what acts as a scavenger for oxygen in the set reaction of amalgam?

A

zinc

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6
Q

when is amalgam fully set and ready to be polished?

A

24 hours

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7
Q

how long do you have between placement and function of amalgam?

A

15-20 mins

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8
Q

how does corrosion of amalgam occur?

A

electromechanical interaction of different alloy phases with saliva as the electrolyte

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9
Q

what can corrosion products of amalgam provide?

A

a good marginal seal

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10
Q

what is creep?

A

when amalgam flows out of the cavity and protrudes at the margin
can fracture off and produce ditching

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11
Q

what component of amalgam is toxic to the CNS?

what can it cause?

A

mercury
MS
behavioral and psychiatric problems

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12
Q

how is excess mercury removed?

A

mercury rises to the surface during packing and condensation and is removed by carving

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13
Q

why are bonded amalgams used?

A

not enough tooth structure to give retention

complete marginal seal and prevent ingress of bacteria

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14
Q

what are advantages of amalgams?

A

reduced need to prep
no pins
reduced leakage and sensitivity at margin

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15
Q

what is the process of a bonded amalgam?

A

vitrebond lining
etch prime bond
rely x arc uncured
amalgam

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16
Q

when is an amalgam filling indicated?

A 
poor moisture control
large occlusal load
missing cusp
subgingival
no enamel margins
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17
Q

what are some reasons for using a matrix band?

A

retain material in cavity
recreate a contact point
protect the adjacent tooth

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18
Q

what are the components of composite?

A 
resin matrix
fillers
coupling agent
pigments
activator
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19
Q

what is in the resin matrix?

A

principle methacrylate monomers e.g BISGMA

dilutent monomers e,g TEGMA

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20
Q

what is the filler portion of composite?

A

particles of silica glass and barium oxide
aluminasilicate
borosilicate

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21
Q

what are the 3 types of composite?

A

hybrid
macrofilled/conventional
microfilled/nanocomposite

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22
Q

when does shrinkage of a composite occur?

A

polymerisation of the resin matrix

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23
Q

what component of composite might cause hypersensitivity?

A

HEMA

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24
Q

what depth of composite can be cured per increment?

A

up to 2mm

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25
Q

why cure the last composite increment under a cellulose strip?

A

removes oxygen inhibited layer

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26
Q

what is the action of TEGMA?

A

controls the viscosity

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27
Q

what is the coupling agent used and what is its function?

A

gamma silane

transfers stresses generated under occlusal forces from rigid filler to more flexible ductile matrix

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28
Q

what is the action of camphorquinone?

A

yields necessary free radicals to set off polymerisation
at 460-480 nm = visible blue light
readily generated by quartz halogen lamps

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29
Q

what are the differences between flowable and normal composite?

A

flowable has 50-60% less filler
low wear resistance
more shrinkage

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30
Q

dont use composite when?

A

high occlusal loading
RSC
poor moisture control
HEMA sensitivity

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31
Q

what lamps are used to set composite?

A

quartz halogen
LED
plasma arc - increased shrinkage

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32
Q

powder/Liquid GI, what are the components and how is it set?

A

sodium aluminasilicate and 20% CaF
aqueous solution of acyrilic acid copolymer and tartaric acid to control set
acid/base reaction

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33
Q

powder/water GI, what are the components?

A

sodium aluminasilicate and 20% CaF with vacuum dried polyacid
water or aqueous solution of dilute tartaric acid

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34
Q

what is the problem with hand spatulation of GI?

A

increased porosity because of air incorporation

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35
Q

how does GI bond to tooth? Bond to collagen?

A
  • calcium ions

- H bonding and metallic ion bridging

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36
Q

how do you boost the bond of GI to tooth?

A
  • citric acid - remove smear layer

- polyacrylic acid - boosts tooth bond

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37
Q

properites of GI?

A 
brittle
exothermic chem set
brittle
poor abrasion resistance
acid erosion
radiolucent
F release
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38
Q

what is a cermet?

A

Ag pellized mix of glass and metal particles

poor appearance but better strength

39
Q

what is a modified composite?

A

filler of composite is placed with aluminasilicate glass
encourages fluoride release
light cured

40
Q

what is a giomer?

A

modified composite structure but aluminasilicate glass is pre reacted with a polyacd

41
Q

what are the two setting reactions of a giomer?

A

surface reaction
full reaction
both VLC light cured

42
Q

what is RMGIC?

A

ion leachable glass with methacrylate resin

polyacid, hema, water, chem activators, polymerisation activatos

43
Q

what do RMGIC do in water?

A

expand

44
Q

what are some indications for GI use?

A 
abrasion and erosion cavities
tunnel prep
temp restoration
deciduous teeth
ART
luting cement
root caries
45
Q

what are some indication for RMGIC use?

A

lining
base
sandwhich

46
Q

what is the open sandwich technique?

A

RMGIC on occlusal floor

composite on top

47
Q

what is the closed sandwich technique?

A

RMGIC on occlusal floor and pulpo axial wall

composite on top

48
Q

what are the 2 pastes of CaOH? and how is it set?

A
  1. glycol salicylate
  2. Zno and CaOH
    light set
49
Q

what are some properties of CaoH?

A

high ph = bacteriocidal and beneficially irritant

insulates, radiopaque, compatible

50
Q

what are some disadvantages of CaOH?

A

cant withstand condensation

no coronal seal

51
Q

what are the components of Zinc polycarboxylate and what is its brand name?

A
  1. zinc oxide 2. aqueous solution of polyacrylic acid

Poly F

52
Q

what are some properites of Poly F?

A

high mw = cant penetrate the tubules
F = bacteriostatic
Zn = bacteriocidal and radiopaque
insulates, strong, compatible

53
Q

disadvantages of PolyF?

A

no coronal seal

not obtundant

54
Q

what are the 2 pastes of zinc oxide eugenol? what is its brand name?

A 
l = eugenol and olive oil
p = zinc oxide and hydrogenated resin for reinforcement
55
Q

what are some properties of Kalzinol?

A

slight irritancy is beneficial
zn = bacteriocidal and radiopaque
v. obtundant

56
Q

what are some disadvantages of kalzinol?

A

no seal

not compatible

57
Q

what are the components of zinc phosphate?

A 
p = zinc oxide and other metallic oxides
l = aqueous sol of phosphoric acid with buffers of aluminium phosphate and zinc phosphate
58
Q

what are some properties of zinc phosphate?

A

low pH/low MW = highly irritant
zn = bacteriocidal and radiopaque
compatible
insulates

59
Q

what are some disadvantages of zinc phosphate?

A

no seal

not obtundant

60
Q

what is Vitrebond?

A

GI as a liner

61
Q

what are some properties of vitrebond?

A

low pH/high MW = mildly irritant
F = bacteriostatic
insulates/strong/directly adheres = good seal/compatible

62
Q

when to line a cavity and where?

A

if cavity over 2mm

pulpo axial wall and occlusal floor

63
Q

what is an indirect pulp cap?

A

cavity within 0.5mm of pulp

calcium hydroxide and vitrebond

64
Q

what is a direct pulp cap?

A

exposed pulp covered in calcium hydroxide or mineral trioxide aggregate
DRY WITH COTTON WOOL NOT AIR

65
Q

what are the 3 forms of direct attachment?

A

micromechanical tags
chemical adhesion
complex adhesion

66
Q

how does acid etch work?

A

selective decalcification of enamel prisms = allows tags for bond to flow into

67
Q

what does acid etch increase?

A

surface roughness

surface energy - removes surface contaminants, micromech attachements, increase wetting

68
Q

what are problems with dentine bonding agents?

A

dentine is hydrophilic, vital, covered in a smear layer and has organic and inorganic material

69
Q

what are primers really and what do they do?

A

conditioners

acids - alter surface appearance and characterisitics

70
Q

what are some examples of primers and how do they work?

A

maleic acid, oxalic acid, nitric acid, phosphoric acid
acid base reaction
create tags in dentine/demineralise up to 4 microns

71
Q

what are coupling agents really and what do they do?

A

primers
do the sticking
bond hydrophobic material to hydrophilic dentine
HEMA

72
Q

what are sealers?

A

flow into tubules and seal surface rich in methacrylate

BISGMA and HEMA

73
Q

what is an example of a reversible hydrocolloid?

irriversible?

A

agar

alginate

74
Q

what are alginate and agar both?

A

colloidal suspensions of polysacharides in water

75
Q

what is agar?

A

complex polysachharide based on seaweed
borax gives body
sodium phosphate is a retarder

76
Q

what are alginates/components?

A

sodium or potassium salt of alginic acid
calcium sulphate - calcium ions for linking
sodium phosphate - controls working time, limits availability of calcium ions
fillers

77
Q

how does alginate set?

A

gels by cross linking of calcium ions

78
Q

what is the gelation time of alginate?
spatulation time?
working time?

A

3-4 mins
1 min
30 seconds

79
Q

what should impressions be disinfected in?

A

sodium hypochlorite 5-10 mins

actichlor - 10 tabs per 1 litre - 2 mins immersion

80
Q

how are polysulphides set?

A

condensation polymerisation

81
Q

what are the components of polysulphide?

A

base - terminal and pendant thiol groups, polysulphide prepolymer, plasticiser, inert filler
catalyst - lead dioxide, sulphur, inert oil

82
Q

what are the concerns with polysulphides?

A

lead is a concern

bad smell and taste

83
Q

how are condensation set silicones set?

A

by cross linking of hydroxyl terminated polydimethyl siloxane chains

84
Q

what are the components of silicones (condednsation)?

A
  1. hydroxyl terminated polydimethylsiloxane chains and inert fillers
    2 alkyl silicate. tin compound
85
Q

what is the by product of condensation silicones?

A

alcohol

86
Q

what are the components of silicone addition?

A
  1. fillers, liquid silicone prepolymer with some methyl as vinyl. chlorplantinic acid
  2. fillers. liquid silicone prepolymer. polydimethylsiloxane chains with some methyl as hydrogen
87
Q

how is addition cured silicone set?

A

platinum catalysed set

88
Q

what are the two components of polyether?

A 
base = imine terminated prepolymer and inert filler
catalyst = aromatic sulphonic acid ester with paste forming oils and filler
89
Q

how are polyethers set?

A

cationic ring opening polymerisation

90
Q

how is dental plaster made from gypsum?

A

heated to 120 degrees

91
Q

how is dental stone made from gypsum?

A

steam 125degrees in an autoclave

92
Q

how is densite made from gypsum?

A

boil in calcium chloride

93
Q

as you move from plaster to stone to densite what happens to particle size and porosity?

A

reduced particle size and reduced porosity

94
Q

gypsum may interact with what?

A

alginate

dental materials clinical practice (1 decks)

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