Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A RESTORATIVE SOT > Cons indirect materials > Flashcards

Cons indirect materials Flashcards

1
Q

what material categories are there for indirect restorations?

A

metals, ceramics, metal-ceramics, resin composites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what things affect the selection of metal alloys?

A

cost
castability and handling
physical properties
resin bonding
corrosion and tarnish
biocompatibility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is a constituent of many precious alloys?

A

palladium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

when does palladium have a strong whitening effect?

A

most will appear silver unless gold content is >40% and palladium is <6%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

which alloys are more prone to corrosion?

A

those of low noble metal content

(noble metals are metals that resist chemical action and do not corrode and are not readily attacked by acids)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the noble metals? (relevant to dent)

A

silver gold platinum palladium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

can crowns cause lichenoid reactions?

A

cheap alloys may but currently unknown effects
amalgams commonly cause lichen planus (and lichen planus near crowns may be due to an amalgam core)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe nickel-chromium alloys - strength with luting agents? stiffness? sensitivity?

A
  • good bond strength can be achieved between certain Ni-Cr alloys and resin luting agents
  • they are stiffer than most noble alloys and thus can be used in slightly thinner sections
  • avoid inhalation of Ni-Cr casting fumes
  • avoid if sensitive to nickel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why might beryllium be used in Ni-Cr alloys?

A

improve physical properties of the alloy eg hardener and structure refiner

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are Ni-Cr actually used for?

A

they are base metal alloys used to make indirect restorations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

when is rigidity in thin section needed?

A

preventing flexion of long span bridges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe titanium

A

biocompatible
requires high temp for casting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what material properties must the alloy for cast post and cores need and why?

A

high modulus of elasticity
high yield strength

to avoid the post bending or breaking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why should you avoid cheap alloys for cast post and cores?

A

they may corrode or cast poorly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what does proper heat treatment of gold alloys for posts and cores ensure?

A

it will ensure a stiff post which is less likely to bend

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are dental ceramics are what is their structure?

A

also termed porcelains
composite structure consisting of crystalline phases or phases within a glassy matrix
consist of oxides, largely metals and silicsa, essentially inert materals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what can ceramics (although inert) be attacked by?

A

APF gel
(acidulated phosphate fluoride) gel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the most common material used for PJCs?

A

aluminous porcelain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

aluminous porcelain is highly aesthetic. should we use it to restore teeth?

A

prone to fracture so not reliable for restoring posterior teeth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how are porcelains strengthened these days?

A

rely on having a crystalline phase dispersed within a glassy matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what porcelain materials are suitable for posterior crowns?

A

in-ceram and procera allceram

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the most common technique of making PJCs and veneers?

A

sintering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how can ceramics be classified?

A

based on fusion temperature and mode of manufacture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what should you consider when choosing a ceramic (7)?

A

strength of the ceramic
tooth reduction
marginal fit
aesthetics
abrasion of opposing tooth
supported by studies?
cost

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is an important consideration for strength of ceramics?

A

resin cements - esp with veneers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what can affect the effectiveness of resin bonding?

A

a poor bond will not enhance strength of the restoration
some ceramic cores are smooth internally and resistant to etching which prevents effective resin bonding unless specific silanisation techniques are used (eg In-Ceram)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is a typical PJC reduction?

A

1mm shoulder and 1.5mm incisal reduction for anterior teeth
2mm occlusal reduction for posterior teeth

destructive!!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what does loss of cement lute under crowns have indications for?

A

secondary caries and periodontal disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what affects aesthetics of crowns?

A

glazing (adjustments and wear might ruin this)
translucency
colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

which metal-ceramic allots have advantages when rigidity is needed?

A

high palladium low gold alloys have significant advantages over high gold alloys where rigidity is needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what can stress concentrations within PJCs lead to and what can stop this?

A

stress concentrations within PJCs often lead to cracks propagating outwards from the sit surface of the restoration
a tough metal coping bonded to the ceramic will help stop cracks developing in this way

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is used to promote adhesion of alloy to ceramic?

A

oxides of gallium, indium and tin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what might too thick an oxide layer result in?

A

too thick an oxide layer can result in ceramic debonding or discolouration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is a coping?

A

a thin metal, resin or ceramic cap covering a prepared tooth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

pros and cons of cast copings

A

good aesthetics hard to achieve
good method of strengthening porcelain
can create a metal occlusal surface (unlike foil copings)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

are foil copings strong enough for posterior restorations?

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

are feldspathic porcelains strong or weak?

A

feldspathic porcelains are weak in tension and strong in compression

rely on bonding to metal and coping design to disspitate tensile stresses

38
Q

composites vs porcelains for crowns

A

composites induce less wear against opposing teeth than porcelains
research still unclear

39
Q

what pre-operative considerations must be made before making a crown?

A
  • expectations of the pt, eg aesthetics, tooth retention,
  • can pt tolerate the restoration eg can pt lie flat for long, degree of mouth opening, maintenance of restorations (from neuromuscular or skeletal disease)
  • operator skill
  • justification for the damage to the tooth
  • can risk of disease/long term damage be minimised?
  • is plaque control good enough?
  • has risk of future caries been addressed? (ESP ROOT CARIES)
  • has risk of damage from occlusion been minimised
  • are the foundations biologically and mechanically sound? periodontal tissues, endodontic state?
  • is tooth strong enough to receive a crown?
  • will preparation be retentive enough?
  • is there enough space for the restoration?
40
Q

which teeth are most likely to suffer from restorations?

A

posterior teeth - furcations and multiple roots difficulty to clean, inaccesible locations

41
Q

how do we combat posterior teeth being an issue?

A

shortened dental arch - give priority to anterior and premolar teeth (meets aesthetic and mechanical function)

42
Q

what factors determine success of a crown to do with the oral environment?

A

plaque control, caries risk, occlusion

43
Q

what can marginal deficiencies lead to?

A

rapid caries progression and potential tooth loss
esp in patients with inadequate plaque control

44
Q

what is caries risk related to?

A

plaque and diet (and the presence of an RPD for root caries)

45
Q

what is the solution for managing root caries?

A

biological not mechanical eg
hygeine and diet

46
Q

how do you eliminate occlusion problems from crowns?

A

know where the contacts are on the tooth you are treating. especially those involved in guiding the jaw movement in lateral and protrusive excursions.
- teeth involved in guidance
- is the tooth a deflective contact or interference to guidance

47
Q

what things can result in gingival problems to do with crowns?

A

poor crown margins
inccorect emergency profiles

48
Q

where should crown margins be placed?

A

SUPRAGINGIVALLY

49
Q

what should you consider when placing a subgingival margin?

A

placed within the limits of the sulcus and the biological width is not encroached on

50
Q

what is the biological width?

A

2.04mm of supracrestal connective tissue attachment and junctional epithelium

51
Q

what happens if a restoration encroaches upon the biological width?

A

an inflammatory response occurs resulting in:
- attachment loss
- apical migration
- pocket formation

52
Q

apart from periodontal issues, what other issues can placement of a subgingival restoration cause?

A

issues with accurate impression taking - causing poor marginal fit

53
Q

what can poorly contoured temporaries cause?

A

problems with impressions because of poor gingival condition

54
Q

what factors affect strength of a tooth for provision of a crown?

A
  • endodontics weakens a tooth
  • extent of existing restoration
55
Q

what factors affect retention of preparation?

A

adequate crown height

56
Q

if there is not enough space for a crown in OVD what can you do?

A

reduce height of opposing tooth (not recommended but maybe in toothwear cases)
make a local temporary increase in vertical dimension to promote axial orthodontic tooth movements (eg Dahl appliance or occlusal composite buildup) - can take several months

57
Q

what should you do before placing your definitive crown when getting it back from the lab?

A

check it on the die
check it in pt mouth without cement

58
Q

what common lab errors can occur affecting marginal fit of the crown?

A

tight proximal contacts
casting blebs on fit surface
overextended crown margins
underextended crown margins
damaged dies
no die spacer

59
Q

what are the 3 types of hard cement?

A

conventional, resin, hybrid of the 2

60
Q

examples of conventional cements and what do they rely on?

A

zinc phosphate
zinc polycarboxylate
glass ionomer

rely on acid-base reaction resulting in the formation of an insoluble salt (cement) and water

61
Q

what do resin based cements set by?

A

polymerisation

62
Q

what mechanisms are there by which cements secure restoration to prepared tooth?

A

non-adhesive luting
micro-mechanical bonding
molecular adhesion

63
Q

what mechanisms correlate to what cements?

A

non adhesive luting and micromechanical retention are main actions for conventional cements
molecular adhesion for resin and hybrid cements

64
Q

what are the advantages of zinc phosphate cement?

A

long track record
good compressive strength
good film thickness
reasonable working time
resistant to water dissolution
(initially acidic) but no adverse effect on pulp

65
Q

disadvantages of zinc phosphate cement

A

low tensile strength
no chemical bonding
not resistant to acid dissolution

66
Q

when would you recommend a zinc phosphate cement?

A

good for conventional crowns and posts with retentive preparations

67
Q

action of zinc phosphate cement

A

micromechanical interlocking between surface irregularities of the crown and tooth

68
Q

are ZOE cements hard or soft?

A

soft - not for definitive cementation of restorations

69
Q

what are soft cements used for?

A

provisional cementation of definitive restorations when a trial assessment period is needed
eg if occlusion or aesthetics are being majorly altered

70
Q

advantages of polycarboxylate cements

A

reasonable track record
good compressive strength
adequate working time
bonds to enamel and dentine
adequate resistance to water dissolution (not as good as ZP)
no adverse pulp effects, less acidic than ZP on mixing

71
Q

disadvantages of polycarboxylate cements

A

low tensile strength
can deform under loading
can be difficult to obtain low film thickness
not resistant to acid dissolution

72
Q

recommendations for polycarboxylate cements

A

traditionally for vital or sensitive teeth
occasionally useful to retain an unretentive provisional crown

73
Q

action of zinc polycarboxylate cements

A

luting cement but can also bond to tooth tissue (and stainless steel!)

74
Q

advantages of glass ionomer cements

A

same as polycarboxylate cement but similar acidity to zinc phosphate on mixing
good compressive strength (higher than ZP?)
fluoride release

75
Q

disadvantages of glass ionomer cements

A

sensitive to early moisture contamination
low tensile strength (higher than ZP)
not resistant to acid dissolution
has been accused of causing post-op sensitivity (but no worse than ZP)

76
Q

recommendations for GIC

A

conventional crowns where pt has had previously high caries rate
alternative default cement to zinc phosphate

77
Q

action of GIC

A

forms considerable bond to tooth tissue

78
Q

advantages of RMGI and compomers

A

good compressive and tensile strengths
reasonable working time
rsistant to water dissolution
fluoride release

79
Q

disadvantages of RMGI and compomers

A

short track record
may expand and crack overlying porcelain because of water absorption

80
Q

recommendations for RMGI and compomers

A

worth trying for metal or metal-ceramic crowns esp where preparation retention is borderline
unclear which RMGI cements can be used safely with ceramic crowns

81
Q

what are the advantages of resin cements?

A

good compressive and tensile strengths
high tensile strength (in comparison to conventional)
resistant to water dissolution
relatively resistant to acid dissolution
can enhance strength of ceramic restoration if bond obtained

82
Q

disadvantages of resin cements

A

film thickness varies substantially between materials
excess material extruded at margin may be difficult to remove especially proximally
marginal leakage due to setting shrinkage?

83
Q

recommendations for resin cements

A

porcelain veneers, ceramic onlays, resin-bonded ceramic crowns
must be used with effective dentine bonding agent
good for when rententive preps are not possible

84
Q

what is richwil crown remover?

A

material not unlike a sticky sweet

85
Q

how can you remove definitive crowns that have been temporarily bonded on?

A

richwil crown remover
finger pressure
matrix band
impact mallet

86
Q

what does die spacing do?

A

achieves space for the cement lute

87
Q

technique for cementing a crown

A

clean prep amd crown with water spray
airdry but do not dessicate prep
mix cement according to manufacturer instruction
coat fit surface with cement - do not overfill
only apply cement to the preparation if cementing a post
seat quickly with firm pressure until all excess cement pressed from margins

88
Q

when should you remove the cement

A

conventional - excess cement left until after cement sets
resin-based - removal before setting

89
Q

when should adequate moisture control be maintained?

A

until cement has set to prevent moisture contamination of the unset material at the crown margin

90
Q

how can you prevent interproximal cement excess?

A

floss down and pass through interdental space

91
Q
A

A RESTORATIVE SOT (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions