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Fixed Pros > EMAX Crowns > Flashcards

EMAX Crowns Flashcards

1
Q

What types of ceramic are there?

A

Glass (contains silica):
-feldspathic (contains high percentage of silica)

Reinforced glass (silica reinforced by filler):

  • Leucite reinforced
  • Lithium Disilicate (Emax)
  • Glass infiltrated alumina

Glass free:
Zirconium oxide (Emax)
Aluminia

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2
Q

What Emax products are used in the adh?

A

IPS Emax CAD and Press
-Lithium disilicate (used to create monolithic/single unit restorations in adh)
(the rest of the cards refer to this type of crown)

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3
Q

Why do glass free ceramics not require a metal coping?

A

Higher flexural strength

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4
Q

What ceramic is used for PBM’s? What is their flexural strengtH?

A

Feldspathic: 60-70 MPa

Leucite reinforced: 120 MPa

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5
Q

What is the flexural strength of lithium disilicate?

A

400MPa

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6
Q

What is the flexural strength of glass filled ceramic?

A

250-650 MPa

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7
Q

What is the flexural strength of glass free ceramics?

A

Aluminia: 600-700MPa
Zirconia: 1120MPa

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8
Q

What is the size of the lithium disilicate crystals which compose lithium disilicate cermaics?

A

5 micrometres x 0.8 micrometres

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9
Q

How do lithium disilicate crowns retain good translucency?

A

Low refractive index

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10
Q

What is special about the crystal alignment in emax crowns?

A

Limit crack propogation

crack deflection

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11
Q

What are the indications for emax press lithium disilicate crowns?

A

All single unit restorations:

  • Anterior, posterior crowns
  • Veneers
  • Thin veneers
  • Inlays, onlays
  • Implants

Short span bridges in low stress environment:
-Anterior bridges

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12
Q

What are the contraindications of emax press lithium disilicate crowns?

A 
Posterior bridges
Long span bridges
Subgingival margins
Severely reduced residual dentition 
Bruxism
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13
Q

What 3 factors should an operator be aware of in shade selection?

A
  • Shade of tooth/restoration
  • Shade of preparation (assists technician in producing final shade of restoration)
  • Shade of cement

(Due to translucency shade of cement can affect shade of final crown)

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14
Q

What are the rules dictating Emax preps?

A
  • Supragingival margins
  • No sharp points/edges
  • All margins should be chamfer
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15
Q

What are the reduction dimensions for anterior emax crowns?

A
  • Incisal: 1.5mm
  • Labial+ lingual incisal 2/3: 1.2mm
  • 1mm chamfer around circumference of tooth
  • Margins should not be in occlusal contact
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16
Q

What are the reduction depths for an emax veneer?

A
  • Labial: 0.6mm for both incisal and gingival 1/3 / 2/3
  • Incisal: 0.7mm
  • Margins should not be in occlusal contact
17
Q

What are the reduction dimensions for an emax posterior crown?

A
  • 1mm chamfer around circumference of tooth
  • Buccal + lingual occlusal 2/3: 1.5mm
  • Occlusal: 1.5mm
  • Margins should not be in occlusal contact
18
Q

What are the minimum dimensions and rules for onlay/inlay preps with lithium disilicate emax crowns?

A

1mm deep x 1mm wide
Proximal boxes should be flared (divergent) and form 100-120 degree angle with outer surface
Cusp reduction 1mm

19
Q

What is the stone used to pour study models for lithium disilicate crowns?

A

Diestone

20
Q

What should be included in the lab form?

A
  1. Pour upper tooth preparation in diestone
  2. Section 11 die
  3. Construct emax crown as per shade description (illustrate a digaram)
  4. Match shape of 11 crown to 21
21
Q

What should be checked at teh cementation appointment?

A
  • Fit
  • Margin
  • Occlusion
  • contact points
  • Contour
  • Aesthetics
22
Q

What conventional cements can be used and when can they be used?

A

Resin, RMGIC, GIC

  • High strength material (lithium disilicate, metal and metal ceramic, oxide/glass free ceramic)
  • Adequate retention (less than 8 degree taper and 4mm+ height)
  • Adequate thickness (1.0mm + anterior, 1.5mm+ posterior)
23
Q

When can adhesive cements be used?

A

All types (including feldspathic and leucite reinforced)

24
Q

How should the fitting surface of the crown be treated prior to cementation

A

Etch with 5% HF acid (ADH have 9%) for 20 seconds

25
Q

What extra step should be taken in using adhesive cement vs. conventional cement?

A

-Silane coupling agent applied to surface, left for 60 seconds and lightly air dried+ follow manufacturer’s instruction (vs just following manufacturer’s instruction)

26
Q

What is the means survival rate of emax crowns?

A

98.4% at 4 years

27
Q

What are the reasons for failure of emax crowns?

A

Fracture: 0.4%
Endodontic: 0.2%
Secondary caries: 0.2%

28
Q

What are the advantages of emax crowns over PBM crowns?

A
  • Metal free thus better aesthetics
  • Can be adhesively cemented
  • Lithium disilicate structure can prevent crack propogation
29
Q

What are the disadvantages of emax crowns vs PBM crowns?

A
  • Not as strong
  • Limited data as to longevity
  • Can not be burnished at margins (PBM lingual metal surface can)
  • Not suitable for long span and posterior bridges

Fixed Pros (20 decks)

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