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Fixed Prosth 2 > Ceramic Restorations > Flashcards

Ceramic Restorations Flashcards

1
Q

Enhanced esthetics due to the absence of metal
and improved light transmission.
-Looks like a tooth!
-Most beneficial for teeth with normally colored
dentin as the dentin color can affect restoration
through it

A

Ceramics

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2
Q

Most realistic restoration that
looks like a tooth!
HIGH esthetic capabilities

A

Ceramics

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3
Q

(3 ways) Why and How does ceramic look so much like a real tooth?

A 
Color Replication
-Ceramics can be tinted/colored to produce 
nearly any tooth shade
Refraction
-Ceramics reflect and absorb light rays 
simulating enamel
Translucency
-Type of porcelain (incisal/dentin/opaque)
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4
Q

Are ceramics tough or brittle?

A

Brittle

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5
Q
  • Defined as the strength of a material in bending

- Stress on the outermost fibers of a bent test specimen, at failure

A

Flexure strength

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6
Q

-Defined as the resistance to fracture when crack present
-Metals –high FT due to plasticity at tip of crack, absorbs energy, making crack
propagation more difficult
-Ceramics –low FT –little plasticity

A

Fracture toughness

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7
Q

Ceramics _____ as they are fired

A

shrink

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8
Q

Are ceramics more of conductors or insulators?

A

Thermal insulators

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9
Q

Do ceramics have low or high fracture strength?

A

Low fracture strength

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10
Q

(why ceramics fail at lower than
expected stress)
-Crack will propagate through material, or until a particle
is met which stops the crack growth.

A

Crack propagation

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11
Q

Increase in number and size of particles does what for crack propagation?

A

Decreased crack propagation

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12
Q

-Strength is reduced in moist environment.
-Stress-dependent chemical reaction between water
vapor and crack tip, causing crack growth and
fracture with comparatively little occlusal loading
(over long periods).

A

Stress Corrosion

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13
Q

-Ceramic powder/liquid is built up and molded (feldspathic porcelain)
-Process of heating ceramic powder once molded
-Called “Firing” the ceramic
-Sintering is the reduction of porosities between particles as the ceramic
becomes more rubbery.

A

Sintering:

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14
Q
  • This is a range of temperature where porcelain starts to become molten.
  • A transition from solid to rubbery.
  • This is typically between 540 and 610 degrees Celcius.
  • This is below the ceramic melting point.
A

Glass Transition Temperature: (Tg)

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15
Q

What temp range do ceramics start to become rubbery?

A

540-610 C

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16
Q
  • Relies on external pressure to sinter and shape the ceramic at high temperature
  • Restoration is made from a Wax pattern (lost wax technique)
  • Also known as High Temperature Injection Molding
A

Heat Pressing:

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17
Q

-Hard Milling
-Already densely sintered material
-Silicate, glass ceramics, resin-based
ceramics

A
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18
Q 
\_\_\_\_ Milling
-Partially sintered material
-Zirconia and Lithium Disilicate (e.Max)
-Sintering to be completed in oven AFTER
manufacture
A

-Soft milling

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19
Q

_____ Milling
-Already densely sintered material
-Silicate, glass ceramics, resin-based
ceramics

A

-Hard milling

20
Q

_____ ceramics

  • Most translucent optical properties
  • Weakest material
  • Feldspathic porcelain
  • Can ETCH
A

Predominately Glass (veneers)

21
Q

_____ ceramics

  • Less translucency
  • increased strength
  • Lithium Disilicate
  • Can ETCH
A

Particle filled Glass Ceramic (eMax)

22
Q

_____ ceramics

  • Low translucency
  • Highest strength
  • Alumina, Zirconia
  • Cannot ETCH
A

-Polycrystalline Ceramic (zirconia)

23
Q

-Can bond tooth to ceramic with the
etchable ceramics
-Use of a “coupling agent” Silane enhances
bond strength
-Resin cement used – either light cure or dual
cure

A

Resin bonding

24
Q

-Dispersed Crystalline phase
– Higher strength
and fracture resistance
-Lithium Disilicate

A

Reinforcement of the crystalline structure

of the ceramic

25
Q

-Stress induced transformation
-Unique to zirconia
-Compressive forces at crack tip retard
crack propagation

A

Transformation Toughening

26
Q

Resin bonding is a high strength cementation procedure, so
bonding ceramics will _____ the ability of the ceramic to
flex. Therefore, adds strength.

A

decrease

27
Q

___% increase in glass ceramic crown strengthHF Etched ceramic surface (retention)
Silane coupling agent (bifunctional monomers form a
chemical bond)
Resin Composite Cement
Etched enamel / dentin –adhesive layer

A

50%

28
Q

-Very thin “sheet” of porcelain as thin as
0.3 to 0.5 mm (minimal thickness)
-Tooth preparation is specific and is
aimed at providing aesthetics and
physical support for the veneer.
-Veneers are not under heavy occlusal
loads.
-These are resin bonded to enamel
-Can be the most esthetic dental
restoration possible
-Can be so thin, underlying tooth color
can affect optical properties.
-Most technically difficult to fabricate

A

Veneers

29
Q

-Enamel flexural strength is around 300 MPa
-Feldspathic Porcelain flexural strength is much
lower at 60-70 MPa
-We discussed how to strengthen the porcelain
material previously. One additional method
to strengthen this porcelain is to add a metal
substructure.
-Yes! The PFM (porcelain fused to Metal
crowns)!
-

A

Feldspathic porcelain

30
Q

-Enamel flexural strength is around 300 Mpa
-Leucite reinforced ceramic flexural strength
is 120-160 MPa
-Would you use this material on a posterior
tooth?
-Crown – No
-Onlay/Inlay – maybe (only where
occlusal force is low)
-Would Resin bonding help strengthen this
material?
-Yes. It can be etched and
therefore retention and strength is
increased with resin bonding.
-Indications – anterior crowns, veneers

A

-Leucite reinforced Ceramic (Empress)

31
Q

-Enamel flexural strength is around 300 Mpa
-Flexural strength for e.Max is 360-500 Mpa
-Finally stronger than tooth alone!
-Due to its increased strength, Lithium Disilicate
is used for:
Veneers
Anterior and Posterior crowns
Anterior bridges (particular cases)
Inlays/Onlays with low occlusal forces
-Can use resin bonding AND other cements like
Resin Modified Glass Ionomer (RMGI)

A

-Lithium Disilicate Ceramic (e.Max)

32
Q 
has a Polycrystalline structure-This provides increased strength
-This provides a surface that is not 
abrasive like porcelain, but 
instead is gentle on opposing 
dentition.
-Resin Bonding will not increase the 
strength of Zirconia-Resin bonding will do what for 
zirconia?
-Retention!
-Zirconia needs the internal restoration 
surface to be roughened since it 
cannot be etched.  (Zirconia 
contains no glass to etch)-Air abrasion
-diamond bur
A

Zirconia

33
Q

Does porcelain or zirconia need to be roughed on the internal surface nor will resin bonding work on it?

A

Zirconia

34
Q

-Original crown was from Glidewell
Lab 10 years ago.-3Y zirconia crown called Bruxir
-Horrible translucency aesthetic early on
-Poorly defined occlusal anatomy
-3Y Bruxir flexural strength around 1200 Mpa
-Because of its toughness, any cement can
be used.
-Crown has to be ”fired” and will shrink to fit.
Shrinks about 25% during firing.

A

Zirconia

35
Q

-Stress induced transformation
-Unique to zirconia
-Compressive forces at crack
tip retard crack propogation Phase transformation from tetragonal (T) to monoclinic (M)
has associated volume increase (3-5%) →high internal
stresses.
-Crack initiated; tensile stress at crack tip causes
tetragonal→monoclinic shape change
-Volume increase with associated compressive
stresses in vicinity of crack tip leading to
crack closure

A

-Transformational Toughening

36
Q

What is the phase transformation that occurs in zirconia during transformational toughening?

A

tetragonal→monoclinic shape change

37
Q

-Adding more _____increases
translucency
-This results in decreased strength

A

Yttria

38
Q 
A \_\_\_\_\_ crown is a porcelain fused to 
Zirconia.
-Early candidates in this market were 
not very successful.  Lots of 
porcelain fractures.  However, 
newer formulations are finding 
greater success and ethetics!
-Monolithic options were/are not very 
esthetic but are much stronger 
and do not fracture easily.  If they 
were esthetic, were they likely to 
be strong?
  • can mask dark dentin cores
A

PFZ

39
Q

Can ceramic or zirconia be cemented with any type of cement?

A

Zirconia

40
Q

If you want the most esthetic anterior restoration, what material would you choose?

  • Veneer – ?
  • Crown – ?
A
  • Veneer – Feldspathic Porcelain

- Crown – e.Max or Empress

41
Q

-If you want the most esthetic posterior restoration, what material would you
choose?
-Crown – ?
-Crown - ?

A
  • Crown – e.Max

- Crown - 5Y Zirconia

42
Q
  • If you have a bruxing patient, what posterior restoration material would you use?
  • Crown – ?
  • Crown – ?
A
  • Crown – 3Y Zirconia

- Crown – Gold

43
Q

-Only adjust after seated and bonded with resin cement (too fragile to
adjust outside the mouth predictably.
-Use fine diamonds with a little water
-Polish with diamond impregnated polishing paste
-Internal surface should not be adjusted if at all possible

A

Glass Ceramic Veneers

44
Q
  • Adjustment outside the mouth is acceptable
  • Fine diamond with a little water
  • Polish with diamond impregnated polishing paste
  • Internal surface should not be adjusted if at all possible
A

e.Max (Lithium Disilicate)

45
Q

-Adjustment outside the mouth is acceptable
-Fine diamond with a little water
-Polish with diamond impregnated polishing paste
-Internal surface needs either air abrasion or diamond bur roughing prior
to cementing!

A

-Zirconia

46
Q 
\_\_\_\_ cements
-Requires moisture free environment
-Required for low strength ceramics
-Why?
-Requires silane coupling agent for etched 
ceramics
-Primer containing MDP 
(methacryloyloxydecyl dihydrogen 
phosphate) placed on zirconia can 
enhance the chemical bond to cements 
containing resin.
A

Resin Cements

47
Q

-Contraindicated in low strength ceramics
-Water absorption with setting of cement
leading to slight expansion and
possible fracture of ceramic at thin
margin area
-Acceptable for Zirconia

A

Resin Modified Glass Ionomer

Fixed Prosth 2 (12 decks)

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