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2nd Year > Dental Materials > Flashcards

Dental Materials Flashcards

1
Q

what are the types of amalgam?

A

conventional

high copper

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2
Q

what is the composition of conventional amalgam?

A 
65% silver
29% tin
6% copper
2% zinc
3% magnesium
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3
Q

what is the composition of high copper amalgam?

A 
40% silver
32% tin
30% copper
2% zinc
3% magnesium
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4
Q

what are the types of alloy morphology that amalgam can come in?

A

lathe cut

spherical

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5
Q

what is the action of the silver tin compound in the amalgam?

A

undergoes setting reaction

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6
Q

what is the action of the copper in the amalgam?

A

strengthens

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7
Q

what is the action of the zinc in the amalgam?

A

scavenger for oxygen

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8
Q

when does amalgam reach its final strength?

A

24 hours

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9
Q

what is creep?

A

amalgam flows manifesting as protrusions at the restoration margins
= produces fractures and ditching

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10
Q

what causes creep?

A

gamma 2 phase

corrosion of the alloy causes mercury to escape into the crevice = causing expansion

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11
Q

what benefits do corrosion products give?

A

marginal seal

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12
Q

what removes mercury from the amalgam?

A

packing and condensation

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13
Q

what are the benefits of bonded amalgam?

A

reduced prep needed
reduced marginal leakage and post op sensitivity
reinforced tooth structure

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14
Q

what is the composition of the resin matrix in composite?

A

methacrylate/dimethacrylate monomers - BISGMA

comonomers - TEGMA

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15
Q

what is the action of the TEGMA?

A

controls viscosity

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16
Q

what is the action of the C to C double bond in composite?

A

allows free radical polymerisation

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17
Q

what are siloranes?

A

contain oxiranes = ring opening polymerisation

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18
Q

what is cationic curing?

A

camphorquinone causes ring opening polymerisation

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19
Q

what is the filler in composite?

A

quartz, silica, glasses - aluminasilicate, boro silicate, barium oxide

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20
Q

what is the coupling agent in composite?

A

gamma silane

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21
Q

in what ways can composite be activated?

A

chemical

light - camphorquinone

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22
Q

what does camphorquinone do?

A

yields necessary free radicals to start polymerisation

generated by quartz halogen lights `

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23
Q

what is the job of the coupling agent?

A

transfers stess generated under occlusal loading from rigid brittle filler to ductile polymer matrix

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24
Q

what is the job of the filler?

A

shock absorber

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25
what are the 4 types of composite?
conventional microfilled hybrid nanocomposites
26
what is the difference in flowable composite compared to conventional?
less filler
27
what is GI?
ion leachable glass and polycarboxylic acid
28
what is the composition of the powder to liquid GI?
p - sodium aluminasilicate glass + 20% CaF | l - aqueous solution of acrylic acid copolymer and tartaric acid to control the set
29
what is the set reaction of powder and liquid GI?
acid base reaction
30
what is the set reaction of powder and water GI?
p - sodium aluminasilicate glass + 20% CaF, vacuum dried polyacid
31
what does hand spatulation when mixing GI cause?
increased air incorporation | increased porosity
32
how does GI bond to tooth surface?
by calcium ions
33
how does GI bond to collagen?
H bonding - metallic ion bridging
34
how can you boost the tooth to GI bond?
citric acid - removes smear layer | polyacrylic acid - increases bond strength
35
what are the properties of GI?
``` F release and uptake brittle poor abrasion resistance acid eroded non radiopaque ```
36
what is a cermet?
silver pelletized mix of glass and metal particles radiopaque f release increased strength
37
what is RMGIC?
modified composite giomers RMGIC
38
what is modified composite?
filler of aluminasilicate glass = encourages F release | light cured free radical polymerisation
39
what is a giomer?
filler = aluminasilicate glass pre reacted with polyacid is pre reacted with glass polyalkenaote complex
40
what is the composition of RMGIC?
p - ion leachable glass l - methacrylate resin - polymerisation set, polyacid - acid/base reaction, HEMA - allows acid and resin to coexist, water - ionisation for acid/base reaction, polymerisation activators and stabilisers
41
when you start to mix P and L of RMGIC what happens?
acid base reaction starts light activation sets off polymerisation chemical activators - moves more rapidly
42
what can happen to RMGIC's?
shrinkage | expansion in water
43
why is adhesion of RMGIC's limited?
lack of free acid lack of sufficient ionic character lack of mobility of active species
44
what is the make up of a phosphoric acid cement?
p - ZnO and other metallic oxides | l - aqeous solution of phosphoric acids and buffers of aluminasilicate phosphate and zinc phosphate
45
how to phosphoric acid cements set?
sets at surface of powder | rapid and exothermic
46
what are the properties of phosphoric cement?
``` low pH/MW = highly irritant thermal and electrical insulator strong radiopaque good compatibility not obtundant non adhesive - no coronal seal ```
47
what is a variant of phosphoric cement?
silicophosphate cements p - aqueous phosphoric acid and buffers l - zinc oxide and aluminasilicate glass stronger, less soluble, leaches F
48
what is the composition of copper cement?
p - zinc oxide, black copper oxide | l - zinc oxide, aluminosilicate glass
49
what is the composition of zinc oxide eugenol?
p - ZnO and hydrogenated resin, accelerator - zinc oxide and aluminosilicate glass l - eugenol and olive oil to control viscosity
50
how does zinc oxide eugenol set?
chelation
51
what are the properties of zinc eugenol?
``` beneficial irritancy bacteriocidal due to zinc radiopaque zinc incompatible with resin composites non adhesive - no coronal seal insulator obtundant ```
52
what is orthoethoxybenzoic acid?
stronger than zinc oxide eugenol p - quartz l - orthoethoxybenzoic acid/eugenol
53
what is the composition of chemically activated calcium hydroxide?
glycol salicylate | zinc oxide calcium hydroxide
54
what is the composition light activated calcium hydroxide? how is it activated? what increases its rate of set?
methacrylate monomer - BISGMA mixed with HEMA polymerisation activation moisture increases rate of set
55
what are the properties of calcium hydroxide?
``` high pH - beneficial irritancy high pH - bacteriocidal insulates radiopaque compatible not strong and no seal ```
56
what is the composition of polycarboxylates?
``` p = zinc oxide l = aqueous solution of polyacrylic acid ```
57
how do polycarboxylates set?
acid base reaction
58
what are the properties of polycarboxylates?
``` acidic - high MW = reduced penetration and mildly irritant F = bacteriostatic stong, insulative, compatible adhesive no seal, not obtundant ```
59
what are the properties of GI?
high mw = mild irritant bacteriostatic due to F release insulates strong, adhesive, compatible
60
what 3 ways can adhesion be achieved by?
- micromechanical attachment - etch/resins - chem adhesion to enamel and dentine - coupling agents/cements - complex - wetting, penetration - modern bonding agents
61
what is acid etch?
acid gel selective decalcification of enamel prisms micromechanical tags into which bonding resin can flow
62
what are the effects of acid etch?
increased surface roughness increased enamel surface energy - removes surface contaminants, increases wetting, facilitates micromechanical attachment
63
what happens if you etch for too long?
calcium phosphate re precipitate
64
why do you wash away etch?
remove debris
65
why do you dry after washing etch away?
enable hydrophobic resin to penetrate and attach
66
what is a primer?
``` dentine conditioner acid maleic acid, oxalic acid, phosphoric acid, nitric acid acid/base reaction with hydroxyapatite opens tubules ```
67
what is a coupling agent?
primer sticks bonds hyrophobic material to hydrophillic dentine HEMA
68
what is a sealer?
sealant flows into tubules and seals dentine with methacrylates, ensures bond BISGMA TEGMA
69
what are the benefits of ormocers as opposed to composites?
less shrinkage | no residual monomers
70
what are the types of impression materials?
non elastic - impression compound/plaster, zinc oxide and eugenol pastes elastic - hydrocolloids - reversible//irriversible synthetic elastomers - polysulphides, silicone rubbers, polyethers
71
what are hydrocolloids?
colloidal suspension of polysulphides in waterb | soluble or gel
72
what is agar?
complex polysaccharide from seaweed gel borax - gives body potassium sulphate - counteracts retardent effects of gypsum
73
what are the advantages of agar? | disadvantages?
A- reversible, takes up moisture | D - complicated equipment, cost, cross infection
74
what are alginates made up of?
Na/K salt of alginic acid CaSO42H2O - source of Ca for cross linking sodium phosphate - controls working time inert filler - body for manipulation
75
how does sodium phosphate control the working time?
limits the availability of calcium ions

2nd Year (4 decks)

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