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DMS Flashcards

1
Q

adv of non-y2 amalgam

A

high corrosion resistance
more durable
less creep
compressive strength
longer rests
lower marginal breakdown and ditching
reduced post-op sensitivity

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2
Q

how do you remove y2 from amalgam structure

A

high copper alloy >=12%, allowing tin to preferentially react with copper instead of mercury

formation of Cu5Sn6 phase instead of y2

lathe cut particles

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3
Q

originally, why was it necessary to add zinc to amalgam

A

as a scavenger/oxidiser to remove oxygen during manufacturing process
prevent oxidisation of other metals
improve handling and longevity

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4
Q

what effect could occur in freshly placed amalgam rest as result of presence of zinc in amalgam

A

moisture contamination leading to gradual expansion, marginal discrepancies, fractures, microleakage

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5
Q

explain the mechanism of expanding zinc amalgam

A

moisture contamination
zinc and water react to form zinc hydroxide and hydrogen gas
build up of gas causes internal expansion of amalgam, causing dimensional change

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6
Q

symptom of zinc amalgam expansion

A

pulpal pain

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7
Q

what is amalgam setting reaction

A

ag3sn + Hg

Ag3Sn + Ag2Hg3 + Sn8Hg

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8
Q

adv of amalgam

A

high compressive strength
long lasting
cost effective
durable
ease of use
less technique sensitive
high abrasion resistance

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9
Q

disadv of amalgam

A

poor aesthetics
more destructive
high thermal expansion
high thermal conductivity
toxic mercury

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10
Q

adv of composite over amalgam

A

better aesthetics
reduced thermal expansion/conductivity
less destructive
biocompatible
chemical bonding with tooth

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11
Q

components of composite

A

filler particles =
silica, glass, quartz

resin =
BISGMA

camphorquinone =
initiator, light cure activated

low weight dimethacrylate =
TEDGMA

silane coupling agent

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12
Q

name different types of composite

A

flowable
bulk fill
hyrbid
microfilled
macrofilled
nano

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13
Q

what are clinical disadvantages of composite and how are they minimised

A

technique/moisture sensitive =
adequate isolation w cotton wools, dam

polymerisation shrinkage =
place in increments

adhesive bonding =
correct etch bond cure technique

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14
Q

indications for resin bonded bridge

A

favourable occlusion
good quality enamel abutments
large surface area abutments
short span
young
good OH
simplifies RPD

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15
Q

contraindications for resin bonded bridge

A

unfavourable occlusion
poor OH
long span
parafunction
heavily restored abutments
poor abutment alignment
perio involved
mobility
excess soft tissue loss
contact sports

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16
Q

how do you cement a porcelain bridge

A

panavia
etch with hydrofluoric acid
dual cure resin cement with 10MDP monomer

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17
Q

how do you cement a metal bridge

A

sandblast with alumina oxide
GIC cement

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18
Q

how is the surface of porcelain veneer treated in lab to improve adhesion

A

etched with hydrofluoric acid
silane coupling agent

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19
Q

if using composite resin cement, what material ensures good bond to porcelain

A

silane coupling agent

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20
Q

chemically, how does silane coupling agent work to ensure good bond to porcelain

A

chemical bond
silane chemical bond to porcelain, reactive group bonds w composite

silane reacts with silica on porcelain, forming siloxane bond

methacrylate group of silane bonds with composite resin by free radical polymerisation

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21
Q

when is silane coupling agent used in dentistry

A

fibre posts
ceramic
porcelain crowns
inlays/onlays
LiDiSi

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22
Q

when is a dual cure cement indicated

A

both light and self needed
where light will not be able to fully penetrate

porcelain/emax crowns onlays
fibre posts

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23
Q

what concerns do pt have about use of amalgam

A

poor aesthetics
toxic
mercury content
allergy
health risk
side effects
news

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24
Q

how to give pt reassurance on amalgam

A

may release small amounts of gaseous mercury
remains at safe level
isn’t enough for toxic effects
no evidence it has harmful health effects
extensive research + regulatory approval
use for decades

25
what aspects of cavity prep ensure -> caries adequately removed -> finished restoration margins are cleansable
high speed to full extent, clear ADJ, explore soft/stained clear contact area, matrix band fully adapted and tight, tightly pack amalgam, anatomical features e.g. undercuts, Cavo-surface 90-120*
26
describe the mechanism composite bonds to dentine
acid etch 37% phosphoric to remove smear layer demineralisation and creates microporosities exposure collagen fibre rough + increased bonding surface bonding agent with hydrophilic monomers penetrate collagen network for infiltration for chemical bond hybrid layer formation where dentine collagen fibres are penetrated by resin monomers, creates mechanical + chemical bond polymerisation by light cure creates mechanical interlocking from microporosities by etching chemical bond from resin monomers
27
ideal properties of denture base
fracture resistance high compressive strength, abrasion biocompatible dimensionally stable good aesthetics unaffected by oral fluids
28
constituents of PMMA
powder = PMMA particles, benzoyl peroxide initiator, plasticisers, pigments, co-polymers liquid = MMA monomer, inhibitor hydroquinone, co-polymer
29
give 4 possible faults during PMMA production and explain why they occur
gaseous porosity = air trapped in mixing, not heated equally, fast curing contraction porosity = too much monomer granularity = too little monomer crazing = internal stress due to fast cooling undercuring = free monomer
30
adv of CoCr as a denture base
superior compressive strength/hardness high wear resistance smaller cross section needed corrosion resistance lightweight
31
disadv of CoCr as denture base
difficult to adjust, add teeth to cost aesthetics
32
what undercuts for SS, CoCr, Au clasps
cocr = 0.25 au = 0.5 ss = 0.75
33
ideal properties of impression material
dimensionally stable accurate ease of handling biocompatible adequate working/setting time tear resistance elastic recovery on removal acceptable taste/smell good flowabiltiy surface detail reproduction
34
name 2 non-elastic impression materials
impression compound impression paste
35
name 4 elastomers
polyether addition silicone condensation silicone polysulphide
36
name 2 hydrocolloids
agar alginate
37
what are the constituents of alginate
sodium alginate calcium sulphate silica, fillers, water
38
alginate setting reaction
sodium alginate + calcium sulphate = calcium alginate + sodium sulphate
39
adv of alginate
cheap acceptable taste/smell non-irritant non toxic ease of use
40
disadv of alginate
poor tear strength not 100% elastic recovery dimensionally unstable limited detail accuracy
41
uses of alginate
primary imps secondary imps ortho study models
42
advantages of elastomeric impression
higher dimensional stability better detail reproduction reduced water sorption + shrinkage
43
GI composition
acid/liquid = poly acrylic acid base/powder = calcium fluoroaluminosilicate glass, silica, alumina
44
describe the setting reaction of GI
dissolution = H+ ions attack glass, ca/al/f ions released, leaves unreacted silica gelation = initial setting due to ca2+ ions crosslinking with poly acrylic acid by chelation with carboxyl group hardening = trivalent al increases crosslinking, al polyacrylate formation, takes few days
45
use of GIC
restorative cavity liner stainless steel crown cementation metal onlay cementation
46
properties of GIC
fluoride release ok aesthetics thermal expansion similar to dentine biocompatible
47
RMGI vs GI liner
rmgi better - on demand set - increased physical prop e.g. strength, resistance - better bonding to dentine
48
why bad idea to use filler material GI as a luting agent
thicker, can stop correct seating too viscous increased fracture risk less flexural strength
49
luting cement for metal post cure
GIC
50
luting cement for porcelain veneer
dual cure resin cement
51
carbon fibre post
dual cure resin cement
52
ideal properties of luting cement
good adhesion biocompatible low solubility adequate working time good mech props
53
why is RMGI not as good luting cement
contains HEMA which is cytotoxic swells, no bonding with indirect lower bond strength compared to resin
54
how do you bond a porcelain veneer
etch with hydrofluoric acid 4-9% silane coupling agent dual cure resin cement
55
how do you bond non-precious metal
surface prep via sandblast with aluminium oxide GI cement
56
temp bond components
zinc oxide eugoenol resin fillers
57
can you bond zirconia??
no needs sandblasted with aluminium oxide GIC cement
58
why are lithium disilicate crowns so strong
high crystalline content interlocking crystals reinforce glass matrix and block crack propagation high fracture resistance 400MPa flexural strength

BDS4 PP (12 decks)

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