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Bdj Questions > Crowns And Other Extra Oral Restorations > Flashcards

Crowns And Other Extra Oral Restorations Flashcards

1
Q

What are the categories of materials available for crowns and other extra coronal Restorations

A

All metal
Ceramics
Metal ceramics
Resin composites

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2
Q

What are the different types of cement?

A

Conventional or adhesive

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3
Q

What are all metal Restorations

A

These include crowns onlays and shims

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4
Q

Do onlays rely solely on adhesive retention?

A

Yes

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5
Q

What alloys are used in all metal Restorations

A

Low conc of noble metals or entirely base metals

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6
Q

What factors influence alloy selection

A 
Cost
Castability and handling
Physical properties
Resin binding
Corrosion and tarnish
Biocompatibility
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7
Q

What is palladium

A 
Palladium is a silvery white metal used to form a cheaper white gold. It was the fist noble metal used to form precious alloys
Palladium silver
Palladium silver gold
Gold silver copper palladium
Palladium copper
Palladium tin
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8
Q

What does palladium look like

A

Palladium has a strong whitening effect which means that most of these alloys will have a silvery appearance unless the gold content is greater than 40% and the palladium less than 6%

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9
Q

What is the disadvantage of using palladium?

A

Unfortunately palladium and silver absorb oxygen with molten which can result in porous castings especially if casting buttons are reused

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10
Q

What effect does reducing the gold content have on the alloy

A

Owners the specific gravity (density) which may make casting less reliable than with high gold alloys
Why?
Because Less dense alloys have lower kinetic energy during casting which in turn reduces the penetration of moten metal into the mould.

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11
Q

Advantages of high gold alloys

A

High gold alloys have excellenr Corrosion resistance which implies that few metal ions are eluted from Restorations
Allergies are rare

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12
Q

Gold and palladium alloy key points:
Porous castings can result from _____
Some alloys especially those of low noble metal content are prone to ______
The potential for cheap alloys to cause a ____ reaction is unknown but must be kept in mind

A

Porous castings can result from reusing casting buttons

Some alloys especially those of low noble metal content are prone to Corrosion

Lichenoid

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13
Q

What base metal alloys are used to make indirect Restorations

A

Nickel chromium
Nickel chromium beryllium
Titanium
Pro gold

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14
Q

What are the most commonly used alloys

A

Nickel chromium and nickel chromium beryllium

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15
Q

Why is beryllium added

A

To improve the alloys physical properties: it’s used as a hardner grain structure refiner and to reduce the alloys fusion temperature

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16
Q

Why might some alloys contain molybdenum instead of beryllium

A

The concerns over health

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17
Q

All the base metal alloys have a higher modulus of elasticity than noble alloys?

A

True

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18
Q

What are the base metal alloys

A

Nickel chromium
Nickel chromium beryllium
Titanium
Pro gold

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19
Q

Is nickel chromium a base metal alloy used to make indirect restorations

A

Yes

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20
Q

What is the advantage of using base metal alloys over the precious metal alloys given the higher modulus of elasticity?

A

The advantage of using base metal alloy given the higher modulus of elasticity than noble alloys means they are more rigid
Which is helpful in preventing flexion of long span bridges

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21
Q

Why is rigidity in thin section necessary?

A

For adhesive Bridge frameworks and for adhesivelh retained shims used to restore the palatal surfaces of worn incisors

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22
Q

What advantage do base metal alloys with high modulus of elasticity have in resin bonded bridgework

A

It is possible with selected resin adhesives to obtain high bond strengths to the surface of the sandblasted alloy
Eg nery et Al reported a bond strength of 22 Mpa for a nickel chromium alloy bonded to dentine with AllBond2

23
Q

True or false precious metal alloys have a lower bond strength than base metal alloys

A

True base metal alloys have a higher bond strength

24
Q

True or false a good bond strength can be achieved between Ni Cr alloys and resin luring cements

A

True

25
Q

Can Ni Cr alloys achieve a good bond strength with resin luring cements

A

Yes

26
Q

Are Ni Cr alloys stuffer than most notable alloys

A

Yes

27
Q

Why can Ni Cr alloys be used in slightly thinner section than other alloys

A

Ni Cr alloys are stigger than most noble alloys so can be used in thin section

28
Q

Why is there a health concern with using some base metal alloys in fabricating indirect restorations?

A

Technicians and dentists possibly inhaling Ni Cr casting fumes or grindinf dust especially if the alloy contains beryllium

29
Q

If the pt is sensitive to nickel what should be avoided

A

Using Ni Cr alloys should be avoided on pts 2ith hypersensitive to Ni

30
Q

What is the concern with using nickel as a base metal alloy

A

Nickel is known to cause contact dermatitis

31
Q

What are the health risks associated with beryllium

A

Acute: conjunctivitis dermatitis bronchitis

Chronic beryllium disease may not express itself for several years after exposure

32
Q

What are the health risks of nickel

A

Dermatogical and lung problems
High levels of nickel or nickel compounds are carcinogenic
Tumous: rhabdomyosarcoma nasopharyngeal and lung carcinoma

33
Q

What precautions can technicians and dentists take when working with beryllium and nickel

A

Ensure adequate exhaust and filtration system. So the grinding and cast fumes of beryllium are removed.
And when fitting a Ni Cr restoration use adequate aspiration during adjustment

34
Q

What is the technical difficulty technicians have with base metal alloys

A

Basse metal alloys are hard to adjust and difficukt to finjsh

35
Q

What is the percentage in the population of sensitivity to nickel

A

10-20% women

1-2% men

36
Q

Titanium key points
Specialised casting requires what?
Restorations can alse be ____________ using spark erosion

A

Specialised casting requires an argon arc under vacuum

Restorations can also be electroformed using spark erosion

37
Q

Cast post and cores key points
Avoid cheap alloys which may _________ or ________ _________
The alloy needs to have a high modulus of elasticity and high yield strength
Proper heat treatment ensures ________________________________

A

Cast post and cores::
Avoid cheap alloys which may corrode and cast poorly
The alloy needs to have a high modulus of elasticity and high yield strength
Proper heat treatment ensures a stiff post which is less likely to bend

38
Q

What qualities are needed for materials used as cast post and cores

A

High modulus of elasticity
High yield strength
Proper heat tx to ensure stiff post less likely to bend
Corrosion resistant

39
Q

What properties does titanium have?

A

Biocompatibility
Restorations can be either cast or electro formed (milling of titanium blank by spark erosion)
Casting requires high temp (1650¢) and a special magnesium investment
Must be cast under vacuum to prevent oxidation of titanium

40
Q

What is required in the casting of magnesium

A

Hugh temperature 1650 degrees
Magnesium investment
Argon arc

41
Q

What is ‘progold’

A

Like brass
Consist largely of copper zinc
So tarnishes easily

42
Q

Does progold tarnish easily? Why

A

Yes because progold is an alloy like brass made from copper and zinc so tarnishes

43
Q

What are the material requirements for cast post and cores

A

High hardness, proportional limit, ultimate tensile stength
Affordable
Easy Castability
Corrosion resistant

44
Q

What allows a more rigid casting, capable of resisting distortion from occlusal forces

A

Proper alloy selection

Heat tx

45
Q

Porosity within a cast post can result in

A

Post fracture with unfortunate consequences

Thin posts are more likely to suffer critical porosity than thicker ones

46
Q

True or false: many gold alloys used for post and cores can be either soft or hard depending on heat tx

A

True

47
Q

A soft post will ______&______ more easily under occlusal load than a hard one

A

Bend and break

48
Q

How may labs unwittingly make a soft post

A

Quenching the hot casting ring to allow the investment to be easily removed
If this is done the casting must be heat treated according to manufacturers specifications

49
Q

What is the usual temperature for heat treating gold alloys

A

400 degrees for 40 minutes

50
Q

How can the need to heat tx be avoided

A

Allowing the casting ring to bench cool

Slowly to room temperature

51
Q

True or false

Some of the alloys used for all metal Restorations can also be used as metal ceramic Restorations

A

True

52
Q

What are dental ceramics

A

Porcelains consisting of oxides largely of metals and silica, and are essentially inert materials
Have a composite structure
Consist of a crystalline phase or phases within a glassy matrix

53
Q

Can dental ceramics be affected by APF gel

A

Yes can be attacked by acidulated phosphate fluoride gel

54
Q

Can ceramic Restorations break under occlusal load

A

Yes
Ceramics are susceptible to stress Corrosion
Slow crack growth

Bdj Questions (14 decks)

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