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BDS4 EXAM PREP > DMS > Flashcards

DMS Flashcards

1
Q

describe how to bond to enamel

A

37% phophoric acid - etch/conditioner
acid roughens surface of the dry enamel, allowing micrmechanical interlocking of resin filled materials

etching inc the suface energy of the enamel suface- imrpove wettability - allows resin to adapt better

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2
Q

3 types of bond to dentine

A

mechanical - molecular entanglement
chemical -
vand der Waals (electrostatic interaction)

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3
Q

why do we need DBA

A

dentine is hydrophillic with low surface energey
DBA is required to inc surface energy

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4
Q

how do DBAs work

A

inc surface energy of dentine
* allow comp resins to flow and stick to surface

also primer/coupling agent - bifunctional molecule with hydrophilic and hydrophobic end
* hydrophillic end bonds to dentine and hydrophobic end bonds to comp resin

contain spacer groups allowing for flex during bonding and may contain filler particles to inc strength

HEMA, 4 META, MDP

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5
Q

smear layer

A

adherent layer of organic debris that remain on the dentine surface after tooth prep
0.5-5um thick

removed by dentine conditioners (etch) or penentrated by self-etching primers

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6
Q

adhesion-decalcification concept

A

interaction of bonding materials with HA

minerals removed from dental hard tissues replaced by resin which, when mineralised mechachinally interlocks in these porosities
* molecular entaglement

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7
Q

cavity liner Vs base

A

liner <0.5mm
base is thicker

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8
Q

function of cavity liner

3

A

protect pulp from chemical and thermal stimuli

prevent microleakage (bacteria and endotoxins)
* prevent gaps/voids/air blows

palliative function (reduce symptoms)

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9
Q

indications for when to place a liner

A
  • deep cavities and direct restoratioins
  • close to pulp
  • pulpitis like symptoms
  • small pulp exposures
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10
Q

examples of cavity liners

A

CaOH
GIC/RMGIC
ZnO

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11
Q

how does CaOH set

A

chelation reaction between ZnO and butyl glycol disilicylate

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12
Q

CaOH
adv
disadv

A

adv - bactericidal, forms tertiary dentine, quick set, radiopaque, easy to use

disadv - low compressive strength, unstable and soluble in oral fluids

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13
Q

GIC
adv

A

bonds to tooth
releases fluoride

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14
Q

ZnO cement examples

5 types; adv and diasdv

A

ZnPO4 - cheap, easy to use, non adhesive, non cariostatic

Zn polycarboxylate - ZnPO4 but bonds to tooth

ZOE - low strenght, highly soluble

RMZOE - inc comp strenght, lower solubility

EBA ZOE - reduced solubility, inc strength

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15
Q

dental ceramic

A

solid material compromising of inorgaic compound of metal, non metal and metalloid atoms primariliy held in ionic and covalent bonds

less kaolin and more feldspar than decroative ceramics

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16
Q

feldspar

how are feldspathic ceramics formed

A

fluxing agents lowers fusion and softening temp of glass

formed from leucite when heated to 1150-1550C
powder melts together to form crown, powder and water mixed and applied to die, heaters in furnance causing sintering

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17
Q

features of conventional felspathic ceramics

4 adv and diadvs

A

best aesthetics
smooth surface
chemcially stable
high comp strength

high hardness - can damage opposing natural teeth

low tensile strength
low flexural strength
low fracture resistancen

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18
Q

static fatigue

A

time dependent reduction in strength even in absence of applied load
likely due to hydrolysis of is-O groups within the material over time in acqueous enviroments

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19
Q

function of metal cored ceramic

A

inc fracture resistance and toughness

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20
Q

how are metal cores bonded

A

metal oxides
helps eliminate defects/cracks on the porcelain surface, micro mechanical, chemical bonds, stressed skin effects

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21
Q

examples alloys and ideal properties of MCC metal/alloys

6

A

CoCr, NiCr, AgPd, high gold allow, low gold alloy

high bond strength
high hardness
high elastic modulus
similar thermal expansion coefficient to porcelin
should avoid discolouring porcelain

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22
Q

features of alumina cores

A

strong
opaque
excellent aesthetics
relatively cheap

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23
Q

what do alumina particles act as

alumina cores

A

crack stoppers
preventing cracks propagating through material and causing fracture

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24
Q

where can alumina cored MCCs be used

A

single posterior crown

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25
Q

what type of zirconia is used and descrive the benefit of this type

A

ytteria stabilised zirconia

normal zirconia mooclinic crystal at room temp - if crack begins when stress crack tip reaches critical level, crystal transforms to monoclinic structure
causes slight expansion of materials adn closes up crack tip

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26
Q

properties of zirconia cores
where can they be used

A

very hard
strong
tough
best aesthetics

crowns and bridges throughout mouth

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27
Q

properties of zirconia cores
where can they be used

A

very hard
strong
tough
best aesthetics

crowns and bridges throughout mouth

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28
Q

how are silica containg ceramics luted to teeth

A

etched with hydrofluroic to produce a retentive suface
ethced surface can be bonded to using a silane coupling agent and bonded to totoh using a bonding agent

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29
Q

how are zirconia cored ceramics luted to teeth

A

no silica and not affected by acid (inert fitting surface)
strong enough to be self supporting and can be luted with conventional cements

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30
Q

impression material
def

A

material used to produce an accurate negative replica of the suface and shape of hard and soft oral tissues

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31
Q

mucostatic

A

displace soft tissues slightly and give an impression of undisplaced mucosa

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32
Q

mucocompressive

A

materials the record an impression of mucosa under load and give an impression of displaced soft tissue

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33
Q

ideal properties of IM

A

accuracy
low viscosity
good surface detail
good surface wetting
able to be disinfected
non toxic and non irritant
complete elastic recovery
low settting shrinkage
flexible
low stiffness

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34
Q

ideal elastic behaviour

A

upon removal
material reaches max amount of strain almost instantly
max strain held during removal
when fully removed, materal instantly return to original strain and returns to pre removal shape

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35
Q

observed elastic behaviour (viscoelastic)

A

upon and during removal
material strain gradually iinc to just below the max amount of strain
when fully remove materials return to almost the initial strain
results in permanent strain/deformation and a permanent change in dimension

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36
Q

possible problems in imp taking

A

poor bond to tray (no adhesive)
lack of occlusal detail (inadequate setting)
ledges
drags
air blows
voids
delimitation
seating error
suface inhibition
inconsistent mixing and surface contamination

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37
Q

alginate

material type

A

irrversible hydrocolloid
elastic
mucostatic

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38
Q

features of alginate

A

non toxic/non irritant
adquate setting time
easy to use
adequate flow
good elastic recovery
poor tear strength
poor stability

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39
Q

components of alginate

6

A

sodium alginate
trisodium phophate
calcium phophoate
filler
flavourings
colours

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40
Q

setting reaction of alginate

A

sodium alginate + calcium sulphate -> calcium alginate + sodium sulphate

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41
Q

polyether e.g.

A

impregum

42
Q

impregum

A

elastomer
polyehter
mucostatic - RIGID when set

43
Q

addition silicone

A

polyether
elastic elastomers
mucostatic

44
Q

how are elastomers formed

A

polymerisation with cross linking of polymer chains
generating elastic properties

45
Q

features of impregum

A

adequate tear resistance
hydrophillic - good if poor moisture control
dimensionally stable
good accuracy
non irritant/toxic

rigid when set - avoid undercuts, hard to remove
long set time

46
Q

features of addition silicones

A

good elastic recovery
reduced shrinkage
high dimensional stabilty
accurate
variety of forms - light, medium body PVS
good tear resistance
non irritant/toxic

hydrophobic - dry teeth to avoid air blows
expensive

47
Q

investment materials
types

A

Refractory material used to surround the wax pattern during the procedure of fabricating the metallic permanent restoration. Forms the mould into which the alloy is cast after the wax has been eliminated

Gypsum-bonded, phosphate-bonded, silica-bonded

48
Q

ideal features of investment materials

A

Expand, porous, strong, smooth surface, chemically stable, easy to remove from cast, easy to use, cheap

49
Q

components of investment materials

A

Binder (form coherent mass),

refractory component (withstands high temp, gives expansion)

50
Q

indications for gypsum bonded investment materials

and types

A

Create study models and casts,
record position and shape of teeth,
treatment planning,
diagnostic wax up,
prostheses construction

Plaster, stone, improved stone (densite)

50
Q

indications for gypsum bonded investment materials

and types

A

Create study models and casts,
record position and shape of teeth,
treatment planning,
diagnostic wax up,
prostheses construction

Plaster, stone, improved stone (densite)

51
Q

features of gympsum bonded investment materials

A

Low hardness,
low strength,
very brittle,
porous,
dimensionally adequate,
stable,
adequate for fine detail reproduction,
convenient setting time

52
Q

setting reaction for gympsum bonded investment material

factors that dec setting time

A

(CaSO4)2.H2O -> 2CaSO4.2H2O

Increased powder, spatulation, impurities, temperature, chemical additives (potassium sulphate; borax increases setting time)

53
Q

hydroscopic expansion

A

Water molecules attracted between crystals by capillary forces, forcing crystals apart.

Increased by low powder/water ratio, increased silica content. higher water temp, longer immersion time

54
Q

lost wax technique

A

Sprue, wax pattern, invest, set, wax burnt out leaving space, expansion, molten alloy cast under pressure, trapped gases escape, cooling to room temp, alloy shrinkage, de-vestment

55
Q

types of luting agents

A

conventional cements (ZnO based)
GIC
comp resins
self adhesive comp resins

56
Q

ideal features of luting agents

A

low viscosity
easy to use
radiopaque
good aesthetics
low/no solubilitiy
biocompatible
cariostatic
good mech properties

57
Q

indications for comp luting agents

A

indirect composites
porcelin
metals (precious and non)

thick so light not penetrate fully

57
Q

indications for dual cure comp luting agents

A

fibre posts
comp inlays
porcelain inlays

thick so light not penetrate fully

58
Q

indication for light cure comp luting agents

A

veneers

59
Q

indications for GIC luting agents

A

MCC
metal posts
zirconia crowns
gold

60
Q

types of metal cooling
consequences of each

2

A

quenching/fast cooling - more nuclei, more grains, small and fine grains

slow cooling - fewer nuclei, fewer grains, large coarse grains

61
Q

why are small fine metal grains better

A

high elastic limit
inc UTS and hardness
dec ductility

62
Q

dislocations

metal

A

imperfections/defects in metal lattic
weak points which lead to an alteration of lattice structure and shape
resistable, occur due to slip
accumulate at grain boundaries

63
Q

impeded dislocation movement
causes

A

inc elastic limit
inc UTS
hardness

dec ductility and impact resistance

64
Q

cold working

metal

A

work hardening/strain hardening

work been on metal/alloy at low temp - below recyrstallisation temp
causes slip - leading to stronger harder metal
e.g. bending, rolling, swaging

65
Q

cold working effect on mech properties of metal

A

inc elastic limit, UTS, hardness
dec ductility, impact strength and corroision resistance

strengthening metal by plastic deformation, dislocations interact and create obstructions in cystal lattice, resistance to dislocation formation develops

66
Q

annealing

metal

A

heating of metal/alloy so that greater thermal vibration allow migration of atoms and atoms rearrange

67
Q

stress relief annealing

metal

A

eliminates internal stresses caused by cold work by allowing atms to rearrange within grains

68
Q

recrystallisation

A

occurs when metal/alloy is heated
leads to smaller equi-axed grains reducing EL, UTS, hardness and inc ductility

spoils benefits of cold working but allows for further cold working

69
Q

alloys
adv

A

improved mechanical properties
lower melting points

70
Q

solid solution

A

common lattice structure containing two metals that are soluble in one another

subsitutional - atomes of 1 metal replace other in crystal lattice; randomed or ordered
interstitial - atoms are markedly different in size and smaller are located in sapces of larger atoms

71
Q

types of alloy cooling

2

A

slowly - metal atoms diffuse through lattice, ensuring grain composition is homogenous but large grains

rapidly - prevents atoms diffusion through lattice, causes coring as composition varies throughouot grain (undesirable) - smaller grains impeded dislocation

72
Q

homogenising annealing

alloys

A

reverse coring

reheats alloy to allow atoms to diffuse and cause grain composition to become homogenous

73
Q

composition and function of stainless steel

A

72% Fe - forms steel
18% Cr - chromium oxide layer inc corroision resistance
7% Ni - improves UTS and corrosion resistance
1.7% Ti - corrosion resistance
0.3% C - forms steel

74
Q

what makes steel stainless

A

> 13% Cr

75
Q

properties of stainless steel

A

light
#resistance
corrosion resistance
high thermal conductivity
impact strength
abrasion resistance
thin in cross section

can # if overworked, mechanical abrasion, fatigue or weld decay

76
Q

PMMA setting reaction

A

free radical addition polymersiation reaction

activation - of initiator to provide free radicals

initiation - free radicals break C=C bonds in monomer and transfer free radical

propagation - growing polymer chain

termination - polymerisation

77
Q

constiuents of PMMA

A

powder
* bezyoyl peroxide iniator
* pre polymerised PMMA beads
* co-polymers
* pigments

liquids
* methacrylate monomer
* inhibitor
* co-polymers

78
Q

properties of PMMA

A

high softening temperature - but avoid boiling water
high termal conductivity
rigid
aesthetics
adeqaute thermal expansion
good abrasion resistance
low fracture toughness
insoluble in oral fluids
cheap
easy to repair
non irritant

79
Q

gaseous porosity

A

monomer boiling
causes gas bubbles in PMMA

80
Q

contraction porosity

A

insufficient pressure during processing or too much monomer

polymerisation shrinkage causes voids

81
Q

constituents of amalgam

A

liquid mercury

silver, tin, copper, zinc

82
Q

types of amalgam and which is best

A

Traditional
Copper-enriched - increased strength and hardness >6%

particle types types
* Lathe-cut
* Spherical (less mercury, higher tensile and early compressive strengths, less sensitive to condensation, easier to carve)

83
Q

setting reaction for amalgam

A

Ag3Sn + Hg -> Ag3Sn + Ag2Hg3 + Sn7Hg9

Copper enriched:AgSnCu + Hg -> AgSnCu + gamma-1 + Cu6Sn5

Weak strength, poor corrosion resistance.

Copper-enriched removes gamma-2 phase, making it stronger and causing less creep
Silver copper is mixed with gamma-2 to make it stronger and less corrosive.

Other methods to reduce corrosion includes polishing margins and avoiding galvanic cells

check

83
Q

setting reaction for amalgam

A

Ag3Sn + Hg -> Ag3Sn + Ag2Hg3 + Sn7Hg9
powder+liquids -> unreacted particles (gamma)+ gamma1 + gamma2

Copper enriched:AgSnCu + Hg -> AgSnCu + gamma-1 + Cu6Sn5

Gamma2 =Weak strength, poor corrosion resistance.

Copper-enriched removes gamma-2 phase, making it stronger and causing less creep
Silver copper is mixed with gamma-2 to make it stronger and less corrosive.

Other methods to reduce corrosion includes polishing margins and avoiding galvanic cells

check

84
Q

indications and contraindications for amalgam

A

Moderate and large-sized cavities in posterior teeth, ability to seat matrix and wedges around tooth, moisture control not brilliant

Anterior teeth, aesthetics paramount, mercury sensitivity, inability to produce retentive cavity, pregnant, child

85
Q

advantages and disadvantages for amalgam

A

User-friendly, strong, durable, good LT clinical performance, radiopaque, high elastic modulus, high
hardness, cheap

Poor aesthetics, no bond to tooth, high thermal diffusivity, destructive prep, marginal breakdown, tooth discolouration, ditching (LT corrosion at margin), lichenoid reactions, amalgam tattoo

86
Q

why are amalgams now zinc free

A

Zinc is a scavenger during production - preferentially oxidises and slag formed/removed.

Materials are now zinc-free due to the reaction of zinc with saliva/blood: Zn + H2O -> ZnO + H2
* Bubbles of hydrogen gas is formed within amalgam.
* Pressure build-up causes expansion. Downward pressure causes pulpal pain. Upward pressure causes the restoration to sit proud of the surface/protrude

87
Q

3 types of composite resin

A

Conventional,
microfine,
hybrid (best - compromise)

88
Q

components of composite

5

A

Filler particles - improve mechanical properties, aesthetics, abrasion resistance, reduce PCS. Glass silica/quartz

Resin - bifunctional molecules that undergo free radical addition polymerisation - bis-GMA

Light activator - photo-active atom catalyst that initiates polymerisation of resins when activated by blue light (430-490nm) - camphorquinone

Low weight dimethacrylates - adjust viscosity and reactivity of resin monomer. TEGDMA

Silane coupling agent - bifunctional molecule binding resin and filler particles

89
Q

indications and contraindications for composite

A

Anterior teeth, where aesthetics important, cores, veneers, indirect inlays/onlays, luting agents, class III, IV, V restorations,

Moisture control impossible, limited tooth structure remaining, posterior teeth with limited finances

90
Q

advantages and disadvantages of composite

A

Good aesthetics, conservative prep, support for remaining tooth tissue, good bond to tooth, low thermal conductivity, good LT clinical performance, no galvanism

PCS (causing micro leakage, etc.), marginal integrity, post-op sensitivity (due to PCS, contraction, insufficient cure - prevent by <2mm increments), low fracture toughness, high elastic deformation, technique sensitive, hydrolytic breakdown, limited depth of cure, high thermal expansion coefficient

91
Q

components of GIC

A

Polyacrylic acid,
tartaric acid,

silica,
alumina,
calcium fluoride
alumnium fluoride

92
Q

setting reaction for GIC

A

MO,SiO2 + H2A -> MA + SiO2 + H2O

Dissolution. Acid added to solution; hydrogen ions interact and attack the glass surface, causing glass ions to be released/leached out. This leaves silica gel around unreacted glass

Gelation. Initial set. Calcium ions crosslink with the polyacid by chelation with the carboxyl groups, forming calcium polyacrylate. Calcium ions are bivalent, so can react with two molecules

Hardening. Trivalent aluminium ions ensure good crosslinking with an increase in strength - takes up to 7 days

93
Q

indications and contraindications for GIC

A

Temporary restoration, luting agent, shallow cervical restorations, where moisture control difficult, dressing, FS, ortho cement, cavity base/liner

Definitive restoration of large posterior cavities, where composite can be placed

94
Q

adv and disadv of GIC

A

Relatively good aesthetics, fluoride release/reservoir, stable strong bond to enamel and dentine, low micro leakage, good thermal properties, no setting contraction

Brittle, poor wear resistance, initial moisture susceptibility, poor handling characteristic s, not excellent aesthetics, susceptible to acid attack and drying out over time 8. Ion exchange with calcium in enamel and dentine and hydrogen bonding with collagen in dentine

95
Q

how does GIC bond to tooth tissue

A

ion exchange with calcium in enamel and dentine and hydrogen bonding with collagen in dentine

CHELATION

96
Q

components for RMGIC

A

Fluoro-alumino-silicate glass, barium glass, pigments

poly acrylic acid, HEMA, tartaric acid, camphorquinone, H2O

97
Q

types of RMGIC

A

Dual cure - acid base, light activation

Tri cure - acid base, light activation, redox reaction

98
Q

RMGIC vs GIC

A

advantages - Better aesthetics, better handling properties, better strength

disadv - PCS, exothermic setting reaction, reduced strength if unreacted monomer (if not light cured)

99
Q

RMGIC vs Composite

A

adv - Easier to use, less moisture sensitive, fluoride reservoir

disadv - Reduced strength, worse aesthetics

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