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1 - BDS4 finals - big topics > DMS > Flashcards

DMS Flashcards

1
Q

stages of acrylic polymerisation

A

activation
- of initiator to provide free radicals
initiation
- free radicals break C=C bond in monomer and transfer free radicals
propagation
- growing polymer chain
termination
- of polymerisation

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2
Q

what types of porosity can occur from the polymerisation reaction of PMMA?

A

gaseous porosity
contraction porosity
granular porosity

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3
Q

How can gaseous porosity occur when making acrylic resin?

A

monomer boiling (100 degrees C)
occurs in bulkier parts
gas bubbles form under resin

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4
Q

how to avoid gaseous porosity (PMMA)

A

Cure slowly

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5
Q

How can contraction porosity occur when making acrylic resin?

A

too much monomer used
insufficient excess material
insufficient clamp pressure

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6
Q

how can granular porosity occur when making acrylic resin?

A

too little monomer used

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7
Q

How does porosity of acrylic resin affect the denture properties?

A

affects strength
affects appearance
rough sensation to tongue
absorbs saliva
- poor hygiene

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8
Q

What are the components of composite resin

A

filler particles - glass
resin
monomer
camphorquinone
low weight dimethacryalates
silane coupling agent

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9
Q

function of camphorquinone in composite resin

A

photoinitiator
activated by blue light
produces radical molecules
- initiates free radical addition polymerisation leading to changes in resin properties

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10
Q

effects of adding filler particles to composite

A

improved mechanical properties
lower thermal expansion
lower polymerisation shrinkage
less heat of polymerisation
improves aesthetics
some are radiopaque

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11
Q

define ‘depth of dure’

A

the depth to which the composite resin polymerises sufficiently

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12
Q

components of a total etch dentine bonding agent

A

dentine conditioner
- 35% phosphoric acid
primer
- adhesive part of agent
- has a hydrophobic/hydrophillic molecule
adhesive
- resin that penetrates into surface of dentine attaching to the primers hydrophobic surface

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13
Q

what is dental amalgam

A

an alloy formed by the reaction of
- mercury (liquid)
- silver, tin, copper and other metals (powder)

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14
Q

properties of y1 amalgam

A

good corrosion resistance

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15
Q

properties of y2 amalgam

A

weak and poor corrosion resistance

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16
Q

why was zinc originally added to amalgam?

A

scavenger during production
preferentially oxidises and slag formed/removed

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17
Q

why is zinc free amalgam now preferred?

A

interacts with blood and saliva
results in H2 bubbled formed within amalgam
- pressure build up causes expansion
- downward pressure leads to pulpal pain
- upwards pressure - restoration proud of surface

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18
Q

what is creep?

A

when a material experiences repeated low level stress levels *below elastic limit)
causes material to flow resulting in permanent deformation

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19
Q

benefits of copper enriched amalgam

A

higher early strength
less creep
higher corrosion resistance
increased durability of margins

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20
Q

give an example of a non-gamma 2 amalgam

A

permite

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21
Q

advantages of amalgam

A

strong
hard
durable
radiopaque
user friendly

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22
Q

disadvantages of amalgam

A

corrosion
leakage
- does not bond
poor aesthetics
mercury
- perceived toxicity
- environmental impact

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24
Q

downsides of zinc phosphate cement

A

low initial pH of 2
- can cause pulpal irritation
- can take 24 hours to return to normal pH
exothermic setting reaction
not adhesive to tooth or restoration
not cariostatic
24 hour set
brittle
opaque

25
downsides of zinc polycarboxylate cement
difficult to mix difficult to manipulate soluble in oral environment at lower pH opaque lower modulus and compressive strength than zinc phosphate
26
how does GIC/RMGIC differ from GI/RMGI filling material?
smaller glass particle size to allow for suitable film thickness
27
how does GIC bond to tooth surface?
ion exchange with calcium in enamel and dentine hydrogen bonding with collagen in dentine
28
advantages of GIC
low shrinkage long term stability relatively insoluble once set aesthetically better than traditional dental cement fluoride releasing cheap self adhesive to tooth substance
29
advantages of RMGIC
incorporation of resin improves material properties shorter setting time longer working time higher compressive and tensile strengths decreased solubility higher bond strength to tooth
30
potential problems with RMGI
HEMA is cytotoxic - residual monomer may irritate/damage pulp HEMA swells in wet environment - can cause conventional porcelain crown to fracture - cannot be used to cement posts as may split root no bond to indirect restoration
31
downsides of composite luting agents
technique sensitive dual cured physical properties reduced by 25% if they are not light cured
32
advantages of composite luting agents
bette physical properties lower solubility better aesthetics
33
function of silane coupling agent when bonding to porcelain
acts as a surface wetting agent strong oxide bond between oxide groups on porcelain surface and silane C=C bond on silane coupling agent reacts with composite resin luting agent
34
What do you need to do to porcelain prior to cementing it as a restoration?
etched with HF add silane coupling agent - as surface is still not hydrophobic after etching
35
How are metals etched?
by sandblasting
36
materials used for bonding to non-precious metals
MDP and 4-META
37
Features of self adhesive composite resin
metal coupling agent is incorporated into composite resin to simplify bonding process - MDP is used in Panavia anaerobic self cure material good film thickness
38
downsides of self adhesive composite resin
moisture sensitive expensive
39
properties of a temporary cement
soft for easy removal - some do not set at all - prep must be physically retentive
40
Why should eugenol containing cements now be used to cement a provisional restoration where the permanent restoration will be cemented with a resin cement?
residual eugenol may interfere with the setting of this type of luting agent
41
limitations of sandblasting
roughens surface but doesn't give the undercut surface of etching - chemical bond required to strengthen bond
42
Ideal luting agents for an MCC?
GIC RMGIC
43
Ideal luting agent for a metal post?
GIC
44
ideal luting agents for a fibre post?
- dual cure composite and dentine bonding agent - self adhesive composite
45
ideal luting agent for a veneer?
light cure composite + dentine bonding agent
46
ideal luting agent for an adhesive bridge
anaerobic cure composite
47
ideal luting agents for a zirconia crown
- GIC - RMGIC - dual cure composite + DBA - anaerobic cure composite - self adhesive composite
48
ideal luting agents for a composite inlay?
- dual cure composite + DBA - self adhesive composite
49
ideal luting agents for a porcelain inlay?
- dual cure composite + DBA - self adhesive composite
50
ideal luting agents for a gold restoration?
- GIC - RMGIC
51
constituents of temporary cements
supplied as two paste systems - base and catalyst/accelerator - base contains ZnO, starch and mineral oil - accelerator contains resins, eugenol or ortho-EBA and carnauba wax
52
GIC uses
filling material core build up - prior to restoration with crown lining - underneath permanent fillings luting - cementing indirect restorations
53
Components of GIC
acid - Polyacrylic acid - tartaric acid base (powder) - silica - alumina - calcium fluoride - aluminium phosphate - sodium fluoride
54
Outline the 3 phases of GIC setting reaction
dissolution - acid into solution - H+ ions attack glass surface - leaves silica gel around unreacted glass gelation - calcium ion cross linking with poly acid hardening - aluminium ion crosslinking
55
downsides of glass ionomer filling material
poor tensile strength lower compressive strength than composite poorer wear resistance than composite lower hardness higher solubility than composite
56
Benefits of gIC
similar thermal expansion to dentine no contraction on setting fluoride release stable chemical bond to enamel and dentine low micro leakage
57
Resin modified glass ionomer uses
dressing fissure sealant temporary Endodontics access cavity filling luting orthodontic cement restoration of deciduous and permanent teeth base or lining

1 - BDS4 finals - big topics (17 decks)

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