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IODC - IRS > Posterior Full Coverage Crowns > Flashcards

Posterior Full Coverage Crowns Flashcards

1
Q

Reason for placing full coverage temporary crowns on compromised teeth?

A

Restore function and morphology
Restore and improve aesthetic
Preserve remaining tooth structure
Improve confidence = psychology

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2
Q

Why are endo tx teeth weak?

A

Loss structural integrity

  1. Prep of access cavity
  2. Loss of roof of pulp chamber
  3. Fragile due to loss dentine elasticity
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3
Q

What are reasons for cusp protection on posterior teeth?

A

For structural integrity

  1. Loss marginal ridge
  2. Substantial loss tooth structure
  3. Heavily restored teeth
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4
Q

What types of restorations are available for posterior teeth?

A
  1. Adhesive
  2. Cusp-coverage cast restoration - onlay, 3/4
  3. Full-coverage
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5
Q

7 points in assessment/ design considerations?

A
  1. Tooth in function
  2. Aesthetic considerations
  3. Adjacent/ opposing teeth
  4. Perio tissue
  5. Pulp, RCT, periodical tissue
  6. Retention of crown
  7. Material
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6
Q

What are ideal perio condition?

A

Optimal plaque control with perio attachment
Alveolar bone levels good
Stabilised perio disease - pocket depth reduction w/ no BOP

If crown placed periodontally compromised tooth may accelerate breakdown perio tissue

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7
Q

Reasons why pulp death may occur following crown prep?

A
  1. Aggressive insult to tooth
  2. Thermal damage
  3. Local anaesthesia - adrenaline reduce blood flow
  4. Desiccation - drying creates negative pressure
  5. Bacterial contamination - tubules large (older pt more sclerosed)
  6. Chemical damage - cements
  7. Osmotic pressure
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8
Q

How many teeth will become non-vital?

A

1-2 in 10 preps

10-20%

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9
Q

How to reduce chance of pulp death?

A

Good pre-op assessment inc. vitality

Shoulder prep of 1.2mm result remaining width of 0.7mm dentine in 50% (50% less 0.7mm) - problem if prominent pulp horns

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10
Q

What should consider when picking material?

A

Balance aesthetic and function

Ceramic: less aesthetic (less translucent) - need thicken stronger material

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11
Q

Adv and disadv of full gold crown?

A

Adv:

  • conservative - minimal reduction
  • gold is strong thin sections
  • ideal bruxism pt
  • can be adjusted intra-orally

Disadv:
- less aesthetic

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12
Q

What are different types of gold and their use?

A

Type I = soft - hard enough stand biting force - used one-surface onlay

Type II = medium - less burnish able but harder - multiple surface onlay

Type III = hard - most common used - metal crowns

Type IV = extra hard = RPDs , not fixed prosthetics

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13
Q

What is the composition of type III gold alloy>

A 
75% gold
10% silver
10% copper 
3% palladium 
2% zinc
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14
Q

Survival rates of gold crowns?

A

97% at 9 years - 94.1% 540 years

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15
Q

Why are metal-ceramic crowns used?

A

Metal core - provide strength
More aesthetic - at cost of tooth tissue

Disadv: extensive buccal reduction, only metal component can be adjusted intra-orally

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16
Q

What are 3 different types of PFM alloys used?

A
  1. High-nobel alloy (min 60% noble metal) - contain small amount tin, indium or ion which provide oxide layer needed for bond w/ porcelain
  2. Nobel alloy (min 25% noble metal) - high strength, durability, hardness, ductility
  3. Base-metal alloy (<25% nobel metal) - less expensive, harder and stronger but less elastic
17
Q

What is noble metal?

A

Gold, palladium, silver - combo

18
Q

What is survival of PFM?

A

5 years = 93.3%

19
Q

What posterior crowns have higher survival?

A

Gold >PFM > all ceramic

20
Q

What/ when all ceramic crown used?

A

High strength ceramic core -layered w/ translucent porcelain
Aestehtic
Low edge strength - need rounded shoulder
Extensive reduction
Intra-oral reduction not possible

21
Q

What is survival of ceramic crown?

A

Acceptable 5 year fracture - 4.4%

Molar > premolar - fracture rate
Posterior >anterior - fracture rate

22
Q

What are Shillingburgs 5 principles?

A
  1. Preservation tooth structure
  2. Retention - prevent dislodgement axial direction
  3. Resistant - resist rotation non-axial direction (lateral load)
  4. Structural durability
  5. Marginal integrity

PolyRatesRasinSlicedMuffins

23
Q

Ideal features of posterior prep?

A
  1. Well-defined and finished margin
  2. Clear finish line
  3. Ceramic margin should be butt-joint round shoulder
  4. Follow gingival contour
  5. Metal margin should be chamfer
  6. Prep line angles best rounded - thin/sharp edge can cause fracture (stress point)
24
Q

How should an all ceramic crown be prepped?

A

Minimal occlusal reduction = 1.5mm (reflect morphology)
Functional cusp reduction = 2mm
Parallel wall for retention - 5 degree taper
Shoulder margin

25
Q

How should PFM crown be prepped?

A

Buccal shoulder - 1.2-1.4mm (accommodate metal and porcelain)
Lingual chamfer- 0.5-0.7mm
Occlusal = 2mm
Functional cusp bevel - structural durability

Where shoulder meet chamfer - wing (chamfer inter proximally) -preserve tooth structure

26
Q

How should full gold crown be prepped?

A

<1mm reduction all way round
Parallel walls - slight taper
Even occlusal reduction
Bevel functional cusp

27
Q

What are the clinical stages of posterior crowns?

A
  1. Phase I
    - Pe-op clinical and radiographic assessment
    - Tx plan and informed consent
  2. Phase II
    - Tooth build up and prep
    - Impression
    - Shade selection
    - Temporisation
  3. Phase III
    - Remove temp and try-in definitive crown
    - Check occlusion and aesthetic
    - Cement and check

IODC - IRS (12 decks)

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