mix Flashcards
(94 cards)
1
Q
what are the 2 types of amalgam?
A
conventional - 6% copper
high copper - 30% copper
2
Q
what are the different forms of amalgam?
A
lathe cut
spherical
admixed
3
Q
what compound takes place in the setting reaction of amalgam?
A
Ag3Sn
4
Q
what chemical strengthens amalgam?
A
copper
5
Q
what acts as a scavenger for oxygen in the set reaction of amalgam?
A
zinc
6
Q
when is amalgam fully set and ready to be polished?
A
24 hours
7
Q
how long do you have between placement and function of amalgam?
A
15-20 mins
8
Q
how does corrosion of amalgam occur?
A
electromechanical interaction of different alloy phases with saliva as the electrolyte
9
Q
what can corrosion products of amalgam provide?
A
a good marginal seal
10
Q
what is creep?
A
when amalgam flows out of the cavity and protrudes at the margin
can fracture off and produce ditching
11
Q
what component of amalgam is toxic to the CNS?
what can it cause?
A
mercury
MS
behavioral and psychiatric problems
12
Q
how is excess mercury removed?
A
mercury rises to the surface during packing and condensation and is removed by carving
13
Q
why are bonded amalgams used?
A
not enough tooth structure to give retention
complete marginal seal and prevent ingress of bacteria
14
Q
what are advantages of amalgams?
A
reduced need to prep
no pins
reduced leakage and sensitivity at margin
15
Q
what is the process of a bonded amalgam?
A
vitrebond lining
etch prime bond
rely x arc uncured
amalgam
16
Q
when is an amalgam filling indicated?
A
poor moisture control large occlusal load missing cusp subgingival no enamel margins
17
Q
what are some reasons for using a matrix band?
A
retain material in cavity
recreate a contact point
protect the adjacent tooth
18
Q
what are the components of composite?
A
resin matrix fillers coupling agent pigments activator
19
Q
what is in the resin matrix?
A
principle methacrylate monomers e.g BISGMA
dilutent monomers e,g TEGMA
20
Q
what is the filler portion of composite?
A
particles of silica glass and barium oxide
aluminasilicate
borosilicate
21
Q
what are the 3 types of composite?
A
hybrid
macrofilled/conventional
microfilled/nanocomposite
22
Q
when does shrinkage of a composite occur?
A
polymerisation of the resin matrix
23
Q
what component of composite might cause hypersensitivity?
A
HEMA
24
Q
what depth of composite can be cured per increment?
A
up to 2mm
25
why cure the last composite increment under a cellulose strip?
removes oxygen inhibited layer
26
what is the action of TEGMA?
controls the viscosity
27
what is the coupling agent used and what is its function?
gamma silane
| transfers stresses generated under occlusal forces from rigid filler to more flexible ductile matrix
28
what is the action of camphorquinone?
yields necessary free radicals to set off polymerisation
at 460-480 nm = visible blue light
readily generated by quartz halogen lamps
29
what are the differences between flowable and normal composite?
flowable has 50-60% less filler
low wear resistance
more shrinkage
30
dont use composite when?
high occlusal loading
RSC
poor moisture control
HEMA sensitivity
31
what lamps are used to set composite?
quartz halogen
LED
plasma arc - increased shrinkage
32
powder/Liquid GI, what are the components and how is it set?
sodium aluminasilicate and 20% CaF
aqueous solution of acyrilic acid copolymer and tartaric acid to control set
acid/base reaction
33
powder/water GI, what are the components?
sodium aluminasilicate and 20% CaF with vacuum dried polyacid
water or aqueous solution of dilute tartaric acid
34
what is the problem with hand spatulation of GI?
increased porosity because of air incorporation
35
how does GI bond to tooth? Bond to collagen?
- calcium ions
| - H bonding and metallic ion bridging
36
how do you boost the bond of GI to tooth?
- citric acid - remove smear layer
| - polyacrylic acid - boosts tooth bond
37
properites of GI?
```
brittle
exothermic chem set
brittle
poor abrasion resistance
acid erosion
radiolucent
F release
```
38
what is a cermet?
Ag pellized mix of glass and metal particles
| poor appearance but better strength
39
what is a modified composite?
filler of composite is placed with aluminasilicate glass
encourages fluoride release
light cured
40
what is a giomer?
modified composite structure but aluminasilicate glass is pre reacted with a polyacd
41
what are the two setting reactions of a giomer?
surface reaction
full reaction
both VLC light cured
42
what is RMGIC?
ion leachable glass with methacrylate resin
| polyacid, hema, water, chem activators, polymerisation activatos
43
what do RMGIC do in water?
expand
44
what are some indications for GI use?
```
abrasion and erosion cavities
tunnel prep
temp restoration
deciduous teeth
ART
luting cement
root caries
```
45
what are some indication for RMGIC use?
lining
base
sandwhich
46
what is the open sandwich technique?
RMGIC on occlusal floor
| composite on top
47
what is the closed sandwich technique?
RMGIC on occlusal floor and pulpo axial wall
| composite on top
48
what are the 2 pastes of CaOH? and how is it set?
1. glycol salicylate
2. Zno and CaOH
light set
49
what are some properties of CaoH?
high ph = bacteriocidal and beneficially irritant
| insulates, radiopaque, compatible
50
what are some disadvantages of CaOH?
cant withstand condensation
| no coronal seal
51
what are the components of Zinc polycarboxylate and what is its brand name?
1. zinc oxide 2. aqueous solution of polyacrylic acid
| Poly F
52
what are some properites of Poly F?
high mw = cant penetrate the tubules
F = bacteriostatic
Zn = bacteriocidal and radiopaque
insulates, strong, compatible
53
disadvantages of PolyF?
no coronal seal
| not obtundant
54
what are the 2 pastes of zinc oxide eugenol? what is its brand name?
```
l = eugenol and olive oil
p = zinc oxide and hydrogenated resin for reinforcement
```
55
what are some properties of Kalzinol?
slight irritancy is beneficial
zn = bacteriocidal and radiopaque
v. obtundant
56
what are some disadvantages of kalzinol?
no seal
| not compatible
57
what are the components of zinc phosphate?
```
p = zinc oxide and other metallic oxides
l = aqueous sol of phosphoric acid with buffers of aluminium phosphate and zinc phosphate
```
58
what are some properties of zinc phosphate?
low pH/low MW = highly irritant
zn = bacteriocidal and radiopaque
compatible
insulates
59
what are some disadvantages of zinc phosphate?
no seal
| not obtundant
60
what is Vitrebond?
GI as a liner
61
what are some properties of vitrebond?
low pH/high MW = mildly irritant
F = bacteriostatic
insulates/strong/directly adheres = good seal/compatible
62
when to line a cavity and where?
if cavity over 2mm
| pulpo axial wall and occlusal floor
63
what is an indirect pulp cap?
cavity within 0.5mm of pulp
| calcium hydroxide and vitrebond
64
what is a direct pulp cap?
exposed pulp covered in calcium hydroxide or mineral trioxide aggregate
DRY WITH COTTON WOOL NOT AIR
65
what are the 3 forms of direct attachment?
micromechanical tags
chemical adhesion
complex adhesion
66
how does acid etch work?
selective decalcification of enamel prisms = allows tags for bond to flow into
67
what does acid etch increase?
surface roughness
| surface energy - removes surface contaminants, micromech attachements, increase wetting
68
what are problems with dentine bonding agents?
dentine is hydrophilic, vital, covered in a smear layer and has organic and inorganic material
69
what are primers really and what do they do?
conditioners
| acids - alter surface appearance and characterisitics
70
what are some examples of primers and how do they work?
maleic acid, oxalic acid, nitric acid, phosphoric acid
acid base reaction
create tags in dentine/demineralise up to 4 microns
71
what are coupling agents really and what do they do?
primers
do the sticking
bond hydrophobic material to hydrophilic dentine
HEMA
72
what are sealers?
flow into tubules and seal surface rich in methacrylate
| BISGMA and HEMA
73
what is an example of a reversible hydrocolloid?
| irriversible?
agar
| alginate
74
what are alginate and agar both?
colloidal suspensions of polysacharides in water
75
what is agar?
complex polysachharide based on seaweed
borax gives body
sodium phosphate is a retarder
76
what are alginates/components?
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
how does alginate set?
gels by cross linking of calcium ions
78
what is the gelation time of alginate?
spatulation time?
working time?
3-4 mins
1 min
30 seconds
79
what should impressions be disinfected in?
sodium hypochlorite 5-10 mins
| actichlor - 10 tabs per 1 litre - 2 mins immersion
80
how are polysulphides set?
condensation polymerisation
81
what are the components of polysulphide?
base - terminal and pendant thiol groups, polysulphide prepolymer, plasticiser, inert filler
catalyst - lead dioxide, sulphur, inert oil
82
what are the concerns with polysulphides?
lead is a concern
| bad smell and taste
83
how are condensation set silicones set?
by cross linking of hydroxyl terminated polydimethyl siloxane chains
84
what are the components of silicones (condednsation)?
1. hydroxyl terminated polydimethylsiloxane chains and inert fillers
2 alkyl silicate. tin compound
85
what is the by product of condensation silicones?
alcohol
86
what are the components of silicone addition?
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
how is addition cured silicone set?
platinum catalysed set
88
what are the two components of polyether?
```
base = imine terminated prepolymer and inert filler
catalyst = aromatic sulphonic acid ester with paste forming oils and filler
```
89
how are polyethers set?
cationic ring opening polymerisation
90
how is dental plaster made from gypsum?
heated to 120 degrees
91
how is dental stone made from gypsum?
steam 125degrees in an autoclave
92
how is densite made from gypsum?
boil in calcium chloride
93
as you move from plaster to stone to densite what happens to particle size and porosity?
reduced particle size and reduced porosity
94
gypsum may interact with what?
alginate
