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BDS4 University of Adelaide Dentistry > Fixed Pros PCPC > Flashcards

Fixed Pros PCPC Flashcards

1
Q

What are the reductions for a PBZ anterior prep?

A 
Occlusal: 2.0mm
Buccal (Occlusal 2/3): 1.5mm
Buccal (Gingival 1/3): 1.0-1.5mm
Proximal: 1.0-1.5mm
Lingual (Occlusal 2/3): 1-1.5mm
Lingual (Gingival 1/3): 1.5mm

Margins: 1.3mm rounded shoulder all around

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2
Q

What are the reductions for a PBM anterior prep?

A 
Occlusal: 2.0mm
Buccal (Occlusal 2/3): 1.5mm
Buccal (Gingival 1/3): 1.0-1.3mm
Proximal: 0.5-1mm
Lingual (Occlusal 2/3): 1mm [Metal + Ceramic], 0.5-0.8 [Metal Only]
Lingual (Gingival 1/3): 0.5mm

Margins:
B: 1mm Flat Shoulder
P+L: 0.5mm Chamfer

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3
Q

What are the reductions for a FGC anterior prep?

A 
Occlusal: 1.0mm (NF cusp), 1.5mm (F cusp)
Buccal (Occlusal 2/3): 1.0-1.5mm
Buccal (Gingival 1/3): 0.5
Proximal: 0.5-1mm
Lingual (Occlusal 2/3): 1mm 
Lingual (Gingival 1/3): 0.5mm

Margins:
0.5mm Chamfer

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4
Q

What material is consider mid way on the spectrum for aesthetics and strength?

A

PBM

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5
Q

When are PBMs indicated?

A
  • Natural Tooth like appearance
  • Max protection for worn/broken/heavily restored teeth (60%+ tooth restored)
  • Other conservative approaches lack structural durability
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6
Q

When are PBMs contraindicated?

A
  • Insufficient Tooth Structure
  • Affordability
  • ## For Superior Aesthetics
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7
Q

What are suitable clinical applications for PBMs?

A
  1. Full Coverage for Cracked/Fractured Teeth [Best]
  2. High Stress/Heavy Occlusion: Deep Overbite, Bruxism
  3. Single Crowns: either anterior/posterior
  4. Retainers/Pontics for fixed Bridge
  5. Reshaping Abutment Teeth for RPD (tilted teeth)
  6. Splinting Periodontally Weakened Teeth (Rare)
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8
Q

T/F: PBM typically has a low gold content

A

False: Gold Content is 50-60%

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9
Q

What is the implication of using higher concentration of base metals in a PBM?

A
  • Cheaper
  • Poorer casting properties
  • Poor control with oxide layer => debonding of porcelain
  • Nickel Sensitivity in patients
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10
Q

What is the implication of using higher concentration of gold in a PBM?

A
  • Optimum bonding to ceramic through thicker oxide layer
  • Superior casting properties
  • Better Colour
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11
Q

What is the thickness of the metal coping in a PBM?

A

0.3-0.5mm

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12
Q

What colour is the metal coping in PBM?

A

Opaque metallic grey

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13
Q

What are the 4 types of ceramic layers in a PBM?

A
  1. Opaque Porcelain: masks metal
  2. Dentine (Body) Porcelain: provides main colour
  3. Enamel (Incisal) Porcelain: provides translucency
  4. Shade layers for furthers aesthetics
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14
Q

What is the thickness of the ceramic in a PBM?

A
  1. 7mm Minimum

1. 0mm Optimum

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15
Q

Why are aesthetics of PBMs inferior to all ceramic crowns?

A

No Light Transmission through metal + opaque porcelain

Light Reflects rather than Refracts

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16
Q

T/F: Modern PBMs have similar wear coefficients to Enamel

A

True, older styles had poor wear coefficients being liable to wear in heavy occlusion

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17
Q

What are the 2 major methods of metal to ceramic bonding?

A
  1. Micromechanical (Clean Metal Surface + Air Abrasion)

2. Chemical Bonding: (At high temperature, metal oxides dissolve into the soften glass phase of porcelain)

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18
Q

What are the 2 minor methods of metal to ceramic bonding?

A
  1. Compressive Forces (Metal Coping Thermal Coefficient > Porcelain)
  2. Molecular Forces (Van Der Vaals initiate)
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19
Q

What are the 8 fabrication lab steps for PBMs?

A
  1. Prepare Tooth
  2. Take Impression
  3. Construct Die
  4. Wax Up
  5. Cast Metal Coping + Oxidise Surface at high temp
  6. Apply Opaque Porcelain (to hide grey metal)
  7. Build up Dentine + Enamel Porcelains for aesthetics (3-4 layers)
  8. Furnacing
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20
Q

What are the shrinkage rates for ceramics during furnacing coalescence?

A

15-20%

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21
Q

What are structure causes of porcelain fractures?

A
  1. Porcelain unsupported by Metal Coping
  2. Stress/Thermal Shock
  3. Thicker porcelain increases sub-surface porosities
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22
Q

What temperature does Porcelain fuse to Metal?

A

960 degrees

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23
Q

What temperature do Noble Metals melt?

A

1260 degrees +

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24
Q

What bur is used for the labial surface of an anterior PBM?

A

Teknik 847

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25
Q

What bur is used for the proximal surface of an anterior PBM?

A

L10

Komet 8877

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26
Q

What bur is used for the palatal surface of an anterior PBM?

A

Komet 8877
Horico 239
F40 (Jasper Special)

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27
Q

What bur is used for the buccal surface of an posterior PBM?

A

Teknik 847

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28
Q

What bur is used for the proximal surface of an posterior PBM?

A

L10

Komet 8877

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29
Q

What bur is used for the palatal surface of an posterior PBM?

A

Komet 8877

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30
Q

What bur is used for the occlusal surface of an anterior PBM?

31
Q

What bur is used for the occlusal surface of an posterior PBM?

A

Teknik 847

32
Q

What bur is used to make a ceramic radial shoulder for a PBM?

A

Teknik 847

33
Q

What bur is used to make a ceramic heavy chamfer for a PBM?

A

Teknik 856

34
Q

What bur is used to make a ceramic rounded shoulder for a PBM?

A

Komet 8877

35
Q

What is the purpose of a functional cusp bevel on a posterior PBM?

A

Ensures 2mm thickness on the functional cusp and reduces risk of fracture

36
Q

What margin is made on the buccal surface of a posterior PBM?

A

1.3mm Radial Shoulder (Teknik 847)

37
Q

What margin is made on the proximal surface of a posterior PBM?

A

Transition from Radial Shoulder to 0.5mm Chamfer margin (Komet 8877)

38
Q

What margin is made on the lingual surface of a posterior PBM?

A

0.5mm Chamfer Margin (Komet 8877)

39
Q

What is the composition of PBZ crowns?

A
  1. Zirconia Oxide ceramic framework

2. Multiple layers of compatible veneering feldspathic porcelain providing aesthetic veneering

40
Q

What are advantages of PBZ crowns?

A

Cheaper cost than PBM
No Metal Allergies
Better Aesthetics (no metal framework)
Faster production time than PBM

41
Q

What are disadvantages of PBZ crowns?

A

Difficult to polish
Scanner unable to interpret sharp line angles
Preparations are more destructive than PBMs

42
Q

What are the lab steps for PBZ crowns?

A

Computer assisted design: Scanned Preps using CAD-CAM

  1. Prepare Tooth
  2. Take Impression
  3. Construct Temporary Crown
  4. Pour Model and Create Die
  5. Wax up Coping + Scan using Piccolo Scanner
    Physical “pointer” runs over the die to take dimensions

Computer assisted manufacturing: Die is milled/cut electronically

  1. Sent Electronically to Manufacturing Site
    Coping milled by machine
    Furnace Sintering
    QA inspection
  2. Return mail to Dental Lab for Ceramic Layering (Eg Nobel Rondo)
43
Q

T/F: Laminating ceramic not base zirconia is liable to fracture

44
Q

What are the reductions for a PBZ posterior prep?

A 
Occlusal: 2.0mm
Buccal (Occlusal 2/3): 1.5-2.0mm
Buccal (Gingival 1/3): 1.0-1.5mm
Proximal: 1.0-1.5mm
Lingual (Occlusal 2/3): 1.5-2.0mm
Lingual (Gingival 1/3): 1.0mm

Margins: 1.3mm rounded shoulder all around

45
Q

What is the functional cusp on a Mx Molar?

A

Palatal Cusp

46
Q

What is the functional cusp on a Mn Molar?

A

Buccal Cusp

47
Q

What are Full Contour Zirconia Crowns?

A

Crowns purely made of Zirconia Ceramics

  • Limited Aesthetics and Colours
  • No ceramic layering (lower risk of fracturing)
  • Strong but more destructive prep than FGC
48
Q

What are features of posterior PBZ crowns?

A
  • Alternatives to FGC: but zirconia only, so limitation in colour
  • Better Aesthetics than PBM
  • Good Strength: but opt for FGC in heavy bruxism cases
  • Cost Effective
49
Q

What are features to consider when prepping an anterior PBZ crown?

A
  1. Smooth, flowing preparation with no sharp points
  2. Rounded Shoulder 1.3mm all way around teeth
  3. Labial and Palatal gingival reductions should be parallel to each other
50
Q

What are features to consider when prepping a posterior PBZ crown?

A
  1. Smooth, flowing preparation with no sharp points

2. Rounded Shoulder 1.3mm all way around teeth

51
Q

How think is the zirconia layer in a PBZ crown?

A

0.6mm. Any layering above this is the laminating ceramic

52
Q

What is the “full” in Full Gold Crown?

A

Full refers to the coverage over the whole crown, not the composition of the metal being fully gold

53
Q

What are indications for FGCs?

A
  1. Where surfaces are weakened/restored
    FGC can tie together remaining tooth structure
    Protects against future fracture
    Can replace existing tooth structure
  2. Short Crowns / Young Teeth
    Where other incisal reductions are too destructive
  3. Heavy Bruxism (Best for)
  4. Bridge Abutment
  5. Reshaping
  6. Splinting Periodontally Mobile Teeth (Not Commonly done anymore)
  7. Low Height Crowns: as less prep is needed
54
Q

Which type of crown should be considered when there is a low height crown?

55
Q

What alloy type is used for FGCs?

A

Type 3: Hard

- 60-70% Gold

56
Q

What are the 4 types of alloy composition for gold crowns?

A 
Type 1 (Soft): 85% Au, Inlays
Type 2 (Medium): 75% Au: Inlays/Onlays
Type 3 (Hard): 60-70%: used for FGC (eg Argenco 2) [EXAM ALERT]
Type 4 (Extra Hard): < 60%
57
Q

What alloy type is used for gold Inlays?

58
Q

What alloy type is used for gold Inlays + Onlays?

59
Q

What alloy type is used for full gold crowns?

60
Q

Why would lower gold alloys be considered

A

Increased hardness

Lower Cost

61
Q

What are the properties of low gold alloys (40-60%)?

A 
Less Ductile (don’t work in thin increments)
Casting Discrepancies
Greater Hardness
Less Corrosion Resistance
Allergy Risk
Toxicity
62
Q

What percentage gold constitutes a low gold alloy?

A

40-60% Gold

63
Q

What properties does gold contribute to FGCs?

A 
Corrosion Resistance
Resists acid attack
Strong in thin sections
Minimum Thickness 0.5mm
Ductility: allowing for smooth burnished margins
64
Q

What properties does copper contribute to FGCs?

65
Q

What properties does silver contribute to FGCs?

A

Reduces melting point, modifies red colour (from gold/copper)

66
Q

What properties does platinum contribute to FGCs?

A

Reduces CTE (Coefficient Thermal Expansion), Increases melting point

67
Q

What properties does palladium contribute to FGCs?

A

Increased hardness, Whitens, Improves Castability

68
Q

What properties does Zinc contribute to FGCs?

A

Improves Castability, Prevents Corrosion

69
Q

What metals comprise the alloys found in FGCs?

A 
Gold
Copper
Silver
Platinum
Palladium
Indium
Zinc
Nickel
70
Q

What are advantages of FGCs?

A
  1. Less Destructive Prep
  2. High Strength
  3. Modification of Tooth Shape / Angulation
  4. Longevity: 97% 1-9 years, Still 94.1% at 40 years: consider when longevity over aesthetics is the main goal of patient
  5. Less destructive than PBMs
71
Q

What are disadvantages of FGCs?

A
  1. Still not conservative: Worse than veneers, better than FGC
  2. Not Aesthetic
  3. High Cost
  4. Galvanic Current: sometimes causes by electricity conductivity difference between gold + amalgam core
  5. Require more technical skills - margins are thinner
  6. Future Pulp Testing Difficult
  7. Iatrogenic Damage Risk
72
Q

What occlusal reduction is done for a functional cusp reduction in a FGC?

73
Q

What occlusal reduction is done for a non-functional cusp reduction in a FGC?

74
Q

What are the steps of a FGC prep

A
  1. Occlusal Reduction
  2. Functional Cusp Bevel
  3. Buccal and Lingual Axial Reduction
  4. Proximal Axial Reduction
  5. Axial Smoothing
  6. Seating Grooves if extra retention needed

BDS4 University of Adelaide Dentistry (2 decks)

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