This document discusses various types of all-ceramic biomaterials used in dentistry. It describes 6 types of all-ceramic materials: 1) sintered ceramics, 2) castable glass ceramics, 3) heat-pressed ceramics, 4) glass-infiltrated ceramics, 5) machined ceramics, and 6) CAD/CAM ceramics. Each type contains different subtypes that are made of materials like alumina, zirconia, lithium disilicate, and leucite to provide different mechanical properties for various dental applications. The document provides details on the composition, fabrication process, strengths and uses of each material.

1. All-ceramic biomaterials
(Part one)
2017

2.  All-ceramics contain a large amount of crystalline
phase (35–99 vol%), which is responsible for
improving mechanical properties.

3. Types of all-ceramic materials
1. Sintered all-ceramic materials
2. Castable glass ceramics
3. Heat-pressed ceramics
4. Glass-infiltrated ceramics (slip-cast ceramics)
5. Machined ceramics

4. Types Subtypes Crystals percentage
1. Sintered
(not available)
Alumina-based Alumina 40–50 wt%
Leucite-reinforced Leucite 45 vol%
2. Castable
(not available)
Mica 45%
3. Heat-
pressed
Leucite-reinforced Leucite 35–45 vol%
Lithium disilicate Lithium disilicate 65 vol%
4. Glass-
infiltrated
(slip-cast)
In-Ceram Alumina Alumina 68 vol%
In-Ceram Spinel Magnesia & alumina
In-Ceram Zirconia Alumina
12Ce-TZP
34 vol%
33 vol%
12Ce-TZP: zirconia stabilized with 12 mol% ceria .
All-ceramic materials

5. Translucency
Leucite > Lithium disilicate & Magnesia > Alumina > Zirconia-based ceramics.
Flexural strength
Leucite < Lithium disilicate & Magnesia < Alumina < Zirconia-based ceramics.
(150) (300) (350–400) (550–600) (650–1400 Mpa)
Highest fracture toughness: zirconia-based ceramics (3Y-TZP & Ce-TZP/A).
 3Y-TZP: Yttria partially stabilized tetragonal zirconia polycrystals.
 Ce-TZP/A: ceria stabilized zirconia/alumina nanocomposite .
Highest elastic modulus: alumina-based ceramics (Procera).

6. 1. Sintered all-ceramic materials
Types
1.1. Alumina-based ceramics
1.2. Leucite-reinforced ceramics

7. Porcelain furnace

8. 1.1. Alumina-based ceramics
 By McLean in 1965.
 Alumina crystals: 40–50% by weight.
 Flexural strength: about 140 MPa (about
twice that of feldspathic porcelain).

9. 1.1. Alumina-based ceramics
(continued)
 Higher elastic modulus and fracture toughness
compared to feldspathic porcelain.
 Veneered with matched-expansion porcelain.

10. 1.2. Leucite-reinforced ceramics
* Leucite crystals: up to 45 vol%.
* Flexural strength: 104 MPa.
* High thermal contraction coefficient.

11. 1.2. Leucite-reinforced ceramics
(continued)
 Large mismatch in thermal contraction between
leucite crystals and glass matrix results in
tangential compressive stresses in the glass
around leucite crystals.
 These stresses act as crack deflectors and
increase the resistance to crack propagation.

12. Note: Sintered all-ceramic restorations are now
being replaced by heat pressed or machined all-
ceramic restorations.

13. 2. Castable glass ceramics
 In 1980s.
 Example: Dicor (Dentsply).
 Tetrasilicic fluormica crystals: 45%
& glass matrix.

14. 2. Castable glass ceramics
(continued)
 Made using the lost-wax technique.
 Flexural strength: about 150 MPa.
 No longer available in the market.

15. 3. Heat-pressed ceramics
 In the early 1990s.
 Pressed at high temperature (920–1180°C)
for 20 min in a phosphate-bonded investment
mold produced by the lost-wax technique.
 Advantages: * Short processing times.
* Good esthetics.

16. 3. Heat-pressed ceramics
(continued)
Disadvantages
 Relatively lower strength compared to alumina
and zirconia slip-cast and machinable.
 Relatively inexpensive equipments.
Types: 3.1. Leucite-reinforced glass ceramics.
3.2. Lithium disilicate glass-ceramics.

17. Lost-wax and heat-pressing techniques

18. Heat-pressing furnace

19. 3.1. Leucite-reinforced glass ceramics
 First generation.
 Example: IPS Empress (Ivoclar Vivadent).
 Leucite crystals: 35–45 vol%
dispersed in a glassy matrix.
 Porosity: about 9%.
 The molding procedure is conducted at 1080°C
for about 20 min.

20. (A) Feldspathic dental porcelain. (B) Leucite-reinforced ceramic.

21. 3.1. Leucite-reinforced glass ceramics
(continued)
 Tangential compressive stresses develop
around the crystals on cooling because of the
difference in the coefficient of thermal expansion
(CTE) between leucite crystals and the glassy
matrix.
 These stresses contribute to crack deflection
and improved mechanical performance.

22. 3.1. Leucite-reinforced glass ceramics
(continued)
 Flexural strength and fracture toughness values
are about double those of feldspathic porcelains.
 Flexural strength: about 150 MPa.
 Indications: inlays, onlays, veneers and anterior
crowns.

23. 3.1. Leucite-reinforced glass ceramics
(continued)
 The use of leucite-reinforced glass ceramic
has declined because of the introduction of
lithium disilicate glass ceramics with improved
mechanical properties.

24. 3.2. Lithium disilicate glass-ceramics
 Second generation.
 In 1998.
 Example: IPS Empress 2 (Ivoclar Vivadent).
 Lithium disilicate crystals: About 65 vol%
dispersed in a glassy matrix.

25. Lithium disilicate crowns (IPS Empress 2).

26. 3.2. Lithium disilicate glass-ceramics
(continued)
 Porosity: about 1 vol%.
 A glass-ceramic ingot is plasticized at 920°C
and pressed into an investment mold under
vacuum and pressure.
 Their strength is more than twice that of
leucite-reinforced all-ceramics.
 Flexural strength: about 300 MPa.

27. 3.2. Lithium disilicate glass-ceramics
(continued)
 Veneered with fluoroapatite-based porcelain
(IPS Eris; Ivoclar Vivadent).
 Indication: 3-unit FPD in the anterior area, and
can extend to the second premolar.

28. Microstructure of heat-pressed lithium disilicate glass-ceramic.

29. IPS e.max Press (Ivoclar Vivadent)
 A newly pressable lithium disilicate glass ceramic.
 In 2005.
 Improved mechanical properties (flexural strength:
440 MPa) and translucency.
 Indications: * Inlays, onlays, and monolithic (full
contour) anterior crowns.
* A core material for crowns and 3-
unit FPD in the anterior region.

30. 4. Glass-infiltrated ceramics
(slip-cast ceramics)
 In the 1990s.
 Condensation of a porcelain slip on a porous
refractory die, which absorbs water from the slip
by capillary action.
 After sintering, the refractory die shrinks more
than the slip. This allows easy separation.

31. 4. Glass-infiltrated ceramics
(continued)
 The sintered porous slip is later infiltrated with a
lanthanum-containing glass, producing two
interpenetrating networks.
 Advantage: higher strength than heat-pressed.
 Disadvantage: long processing times.

32. 4. Glass-infiltrated ceramics
(continued)
Types
4.1. In-Ceram Alumina
4.2. In-Ceram Spinel
4.3. In-Ceram Zirconia

33. 4.1. In-Ceram Alumina (VITA Zahnfabrik)
 In 1989.
 Alumina: 68 vol %, glass: 27 vol %
and porosity: 5 vol %.
 A slurry of densely packed (70–80 wt%) Al2O3
is applied.
Note: slurry means a thick mixture of water and
another substance.

34. 4.1. In-Ceram Alumina
(continued)
 Drying at 120°C for 6 hours.
 Sintered at 1120°C for 2 hours and 1180°C for 2
hours.
 The porous slip is infiltrated with lanthanum glass
at 1100°C for 2 hours to eliminate porosity and
increase strength.

35. 4.1. In-Ceram Alumina
(continued)
 The presence of alumina crystals with a high
refractive index and 5% porosity account for
some degree of opacity.
 Flexural strength: about 550 MPa.
 The core is veneered with feldspathic porcelain.
 Indications: the first all-ceramic system available
for crowns and 3-unit anterior FPDs.

36. Microstructure of alumina slip-cast ceramic.

37. 4.2. In-Ceram Spinel
 In 1994.
 Mixture of magnesia and alumina (MgAl2O4).
 Better translucency, similar to that of lithium
disilicate heat-pressed ceramics, at the expense
of mechanical properties.

38. 4.2. In-Ceram Spinel
(continued)
 Flexural strength: 350–400 MPa.
 Indication: only recommended for anterior
crowns.

39. 4.3. In-Ceram Zirconia (VITA Zahnfabrik)
 Alumina: 34 vol%.
 zirconia stabilized with 12 mol% ceria (12Ce-
TZP): 33 vol%.
 Glass phase: 23 vol%.
 Porosity: about 8 vol%.

40. 4.3. In-Ceram Zirconia
(continued)
 Highest flexural strength and fracture toughness
of all slip-cast ceramics.
 Flexural strength: about 650 MPa.
 Two types of strengthening mechanisms:
(1) Zirconia stress-induced transformation
toughening.
(2) Alumina crack deflection.

41. Microstructure of zirconia-toughened alumina slip-cast ceramic.
A: alumina grains, Z: zirconia grains, Arrow indicates pore.

42. 4.3. In-Ceram Zirconia
(continued)
 The core is veneered with feldspathic porcelain.
 Indications: posterior crown and FPD framework.
 Containdication: anterior regions, since the core
is opaque.

43. 5. Machined ceramics
Types
5.1. Computer aided design/computer aided
machining (CAD/CAM) [CEREC system]
5.2. Copy milling [Celay system]

44. CEREC AC, Sirona Dental System

45. 5.1. CAD/CAM (CEREC system)
 In the early 1970s.
 Types: 5.1.1. Hard machining
5.1.2. Soft machining
 The abutment or die is first scanned.
 The computer software designs the restoration.
 Then, milling the ceramic block by a computer-
aided machine.

46. 5.1.1. Hard machining
 For fully sintered ceramic blocks.
 Final dimensions of the frameworks can be
milled directly.
 Advantages
* Superior fit (in comparison to soft machining),
because no shrinkage is involved in the process.
* Produce restorations in one visit.

47. 5.1.2 Soft machining
 For partially sintered ceramic blocks, followed
by sintering at high temperature.
 In 2001.
 Enlarged frameworks (about 25%) are milled to
compensate for sintering shrinkage.

48. 5.1.2 Soft machining
(continued)
 Advantages: - Easy to mill.
- Save time and tool wear.
 Disadvantage: the benefit of fabricating the
restoration in one visit is lost,
because it requires sintering
after machining.
 Indications: ceramics difficult to machine such
as alumina and zirconia.

49. 5.2. Copy milling [Celay system]
 Milled restorations by duplicating a resin
pattern using a pantographic device similar to
those used for duplicating house keys.
 Unable to approach the sophistication of the
digital systems (CEREC 3D; Sirona Dental
Systems), the Celay system is now obsolete.

50. Types Subtypes Flexural strength
(Mpa)
Uses
1. Sintered
(not available)
Alumina-based 140 Replaced by heat pressed or
machined all-ceramic restorations
Leucite-reinforced 104
2. Castable
(not available)
150 Not available
3. Heat-
pressed
Leucite-reinforced 150 Inlays, onlays, veneers and
anterior crowns
Lithium disilicate 300 3-unit anterior FPDs, and can
extend to the second premolar
4. Glass-
infiltrated
(slip-cast)
In-Ceram Spinel 350–400 Only recommended for anterior
crowns
In-Ceram Alumina 550 Crowns and 3-unit anterior FPDs
In-Ceram Zirconia 650 Posterior crowns and FPDs
5. Machinable
(CAD/CAM) 3Y-TZP 900–1200
- Crowns & FPDs.
- Orthodontic brackets.
- Endodontic posts.
- Implants and implant abutments.
All-ceramic materials

51. CAD/CAM ceramics
(Part two)
2017

52.  All-ceramic restorations can be fabricated by both
traditional laboratory methods and CAD/CAM.
 The traditional laboratory methods
* Time consuming.
* Technique sensitive.
* Unpredictable.
* Could not process high strength polycrystalline
ceramics such as partially stabilized zirconia.

53. CAD/CAM
 Reduce the fabrication time.
 A good alternative for both the dentists and
laboratories.
 Industrially fabricated blocks are more
homogenous with minimal flaws.
 Can be used for fabrication of both all-ceramic
and the veneering porcelain.

54. Types of CAD/CAM ceramics
1. CAD/CAM with feldspathic ceramics
2. CAD/CAM with mica-based ceramics
3. CAD/CAM with leucite-reinforced ceramics
4. CAD/CAM with lithium disilicate reinforced
ceramics
5. CAD/CAM with glass-infiltrated alumina and
zirconia ceramics

55. 6. CAD/CAM with polycrystalline alumina and
zirconia
6.1. Alumina-based polycrystalline ceramics
6.2. Stabilized zirconia-based polycrystalline
ceramics
6.2.1. Yttria partially stabilized tetragonal
zirconia polycrystals (3Y-TZP)
6.2.2. Magnesia partially stabilized zirconia
6.2.3. Ceria stabilized zirconia/alumina
nanocomposite (Ce-TZP/A)

56. 1. CAD/CAM with feldspathic ceramics
 Feldspar (Na,K Al Si3O8) as a major
crystalline phase: 30 vol%.
 Flexural strength: 120 MPa.
 Excellent aesthetic properties
 Indications: veneers, inlays, onlays and
anterior crowns.

57. 1. CAD/CAM with feldspathic ceramics
(Continued)
1.1. VitaTM Mark I (Vita Zahnfabrik)
 In 1985.
 The first CAD/CAM produced inlay & onlay.
 Fine grain feldspathic ceramic block.
 Fully sintered for hard machining.

58. 1. CAD/CAM with feldspathic ceramics
(Continued)
1.2. VitaTM Mark II (Vita Zahnfabrik)
 In 1991.
 Better mechanical properties.
 Flexural strength: 100–160 Mpa.
 Made of materials similar to conventional
feldspathic ceramic.

59. 2. CAD/CAM with mica-based ceramics
 Example: DicorTM MGC.
 Mica crystals: 70%.
 Flexural strength: about 229 MPa.
 Cumulative breakage at 2 years was higher
than for VitaTM Mark II.
 No longer in the market.

60. 3. CAD/CAM with leucite-reinforced ceramics
 Similar in microstructure and mechanical
properties to the first generation heat pressed
leucite-reinforced ceramics.
3.1. ProCAD (Ivoclar-Vivadent).
 In 1998.
 Similar in structure, marginal gap and fracture
load to the heat-pressed ceramic EmpressTM
(Ivoclar-Vivadent).

61. Before and after treatment with all-ceramic restorations (lithium disilicate
IPS e.max Press Tooth 24 inlay; onlays 26, 27; and crowns14, 15, 25)
and CAD/CAM-fabricated leucite ProCAD onlay 16, 26.

62. 3. CAD/CAM with leucite-reinforced ceramics
(continued)
3.2. EmpressTM CAD (Ivoclar-Vivadent)
 In 2006.
 Leucite crystals: about 45%.
 Finer particle size of about 1–5 μm that helps
resist machining damages.
 The powder is first pressed into blocks and
then sintered.

63. 3.2. EmpressTM CAD (continued)
 Flexural strength: about 160 MPa.
 Indication: chair-side single unit restorations.
 Available in:
- High Translucency (EmpressTM CAD HT)
- Low Translucency (EmpressTM CAD LT)
- Polychromatic (EmpressTM CAD Multi)
 The milled restoration can be stained and
glazed.

64. 4. CAD/CAM with lithium disilicate
reinforced ceramics
 Example: IPSTM e.max CAD (Ivoclar-Vivadent).
 In 2006.
 Fully sintered, but partially crystallized.
 The block exhibits a flexural strength of 130–
150 MPa in the pre-crystallized (blue) state.
 Allows simplified machining and intraoral
occlusal adjustment.

65. 4. CAD/CAM with lithium disilicate
reinforced ceramics (continued)
 Crystallize in a chair-side ceramic oven at 850°C
in vacuum for 20–25 min, and changes from blue
to the selected shade.
 Lithium disilicate crystals: 70 vol%.
 Final flexural strength: 300–360 MPa.
 Indication: - Chair-side monolithic (full anatomic)
anterior and posterior crowns.
- Inlay, onlay, and veneer.

66. 5. CAD/CAM with glass-infiltrated ceramics
 In 1993.
 Presintered blocks to fabricate copings which are
further glass-infiltrated.
5.1. CAD/ CAM InCeramTM Spinell
 The most translucent of this group .
 Flexural strength: 350 MPa.
 Indication: anterior crowns.

67. 5.2. CAD/CAM InCeramTM Alumina
 Flexural strength: 450–600 MPa.
 Marginal gap: 70 μm (clinically acceptable).
 Indications: - Anterior and posterior crowns.
- 3-unit anterior FPD.

68. 5.3. CAD/CAM InCeramTM Zirconia
 Flexural strength: 700 MPa.
 Better fit than the slip cast InCeramTM Zirconia.
 Indications: the opacity of zirconia has limited
its use to the posterior crowns and
FPDs.

69. 6. CAD/CAM with polycrystalline
alumina and zirconia
 Polycrystalline ceramics, such as alumina and
zirconia, have no intervening etchable glassy
matrix.
 The crystals are densely packed, and then
sintered.
 The dense crystal lattice reduces crack
propagation resulting in excellent mechanical
properties.
 Indications: crown and bridge copings.

70. 6.1. Alumina-based polycrystalline ceramics
 Example: ProceraTM AllCeram (Nobel Biocare).
 The first fully dense dental polycrystalline
ceramic.
 In 1993.
 More than 99.9% alumina.
 Computer-aided production of enlarged die
(20%) to compensate for the sintering
shrinkage.

71. 6.1. Alumina-based polycrystalline ceramics
(continued)
 Alumina is densely packed (dry pressed) and
then sintered at 1550°C.
 Flexural strength: about 600 MPa.
 The highest strength of the alumina-based
materials, but lower than zirconia.
 The highest elastic modulus and hardness of all-
ceramic materials.

72. 6.1. Alumina-based polycrystalline ceramics
(continued)
 Veneered with matched expansion porcelain.
 Marginal fit: 70 μm (within the range of clinical
acceptance).
 Indications: - Veneers.
- Crowns.
- Anterior FPDs.

73. 6.2. Stabilized zirconia-based
polycrystalline ceramics
Introduction
Advantages of zirconia
 High biocompatibility.
 High strength and fracture toughness.
 Low bacterial surface adhesion
 Low thermal conductivity.
 Low corrosion potential.
 Good radiopacity.

74.  Zirconia is a polymorphic material.
 It has three crystallographic forms:
* Monoclinic (M): from room temperature to
1170°C.
* Tetragonal (T): from 1170°C to 2370°C.
* Cubic (C): from 2370°C to the melting point
(2715°C).

75.  With the addition of stabilizing oxides such as
ceria (CeO2), magnesia (MgO) or yttria (Y2O3),
a partially stabilized zirconia (PSZ) is formed
at room temperature with cubic crystals as the
major phase, and monoclinic and tetragonal
crystals as the minor phases.

76.  It is also possible to form a mono-phasic
material consisting of tetragonal crystals only,
and the material is called tetragonal zirconia
polycrystal (TZP).

77. Transformation toughening of zirconia
 Stress at the crack tip will trigger transformation
from tetragonal to monoclinic phase (T–M
transformation).
 Accompanied by an increase in volume (about
4.5%) as monoclinic crystals are larger in size.
 Induce compressive stress at the crack tip.

78.  Hinder (not totally prevent) the crack propagation.
 Resulting in an increase in mechanical properties.
 Zirconia has:
- High fracture toughness: 9–10 MPa m-1
- High Flexural strength: 900–1200 Mpa
(about twice that of alumina).

79. Low temperature degradation (LTD) of zirconia
 Progressive spontaneous slow transformation
of the metastable tetragonal phase into the
monoclinic phase in the presence of water at
relatively low temperatures (150–400°C).
 Yttria reacts with water vapor to form yttrium
hydroxide, resulting in instability of the
tetragonal zirconia.

80.  LTD initiates at the surface and subsequently
progresses into the bulk of the material.
 Accompanied by an increase in volume, which
causes stress and microcracking.
 Microcracking results in:
* Grain pullout.
* Surface roughness.
* Water penetration.
* Decrease in strength (strength degradation).

81.  Factors affecting LTD
* Stabilizer type, concentration and distribution.
* Grain size.
* Residual stresses.
 Above a critical grain size, 3Y-TZP is less
stable and more susceptible to spontaneous
transformation.
 Smaller grain sizes are associated with a lower
transformation rate.

82.  Higher sintering temperature and time lead to:
- Larger grain size.
- Higher translucency.
- More susceptible to transformation and LTD.

83. Scanning electron micrographs showing the effect of sintering temperature on
grain size in 3Y-TZP sintered for 2 hr. (A) 1,300°C; (B) 1,350°C; (C) 1,400°C;
(D) 1,450°C; (E) 1,500°C; (F) 1,550°C; (G) 1,600°C; and (H) 1,650°C.

84.  Although some concern was raised by the
degradation of femoral heads 20 years ago, no
direct correlation has been established between
LTD and clinical failure of zirconia in dentistry.

85. 6.2.1. Yttria partially stabilized tetragonal
zirconia polycrystals (3Y-TZP)
 Yttria: 3 mol%.
 Radiopacity is comparable to metal.
 Applications
- Crowns & FPDs.
- Orthodontic brackets.
- Endodontic posts.
- Implants and implant abutments.
- Its use in the esthetic zone is limited to the
fabrication of frameworks.

86. 3Y-TZP (continued)
 Colored zirconia frameworks are now available,
and produce a more clinically acceptable color
match.
 Examples for partially sintered blanks
- LAVATM (3M ESPE).
- CerconTM (Dentsply).
- e.maxTM ZirCAD (Ivoclar-Vivadent).
- ProceraTM Zirconia (NobelBiocare).
- VitaTM YZ blocks (Vita Zahnfabrik).

87. 3Y-TZP (continued)
 Examples for fully sintered zirconia blocks: DC
ZirkonTM (Smartfit Austenal).
 Milling the softer partially sintered blanks (green
state): - Shortens the milling time.
- Reduces the wear of milling tools.
 Soft machining of dental restorations requires
sintering at 1350–1550°C for 2–6 hours.

88. 3Y-TZP (continued)
 Porosity after sintering: less than 0.5 vol%.
 Flexural strength: 900–1200 MPa.
 Fracture toughness: 9–10 MPa.m0.5
 Fully sintered Y-TZP blocks have been processed
by hot isostatic pressing.
Note: isostatic means equal pressure from every
side.

89. 3Y-TZP (continued)
 Because of the hardness and poor machinability
of fully sintered Y-TZP, a robust milling system
and extended milling periods are required.
 Milling fully sintered zirconia may compromise the
microstructure and strength of the material.

90. 6.2.2. Magnesium partially stabilized
zirconia (Mg-PSZ)
 Magnesia: 8–10 mol%.
 Tetragonal crystals in a cubic matrix.
 Decreased stability of the tetragonal phase in a
wet environment when compared to 3Y-TZP
after veneering.

91. Mg-PSZ (continued)
 Lower mechanical properties.
 Porosity and large grain size has limited its
success.
 Example: Denzir-MTM (Dentronic) for hard
machining.

92. 6.2.3. Ceria stabilized zirconia/alumina
nanocomposite (Ce-TZP/A)
 Example: NANOZR.
 Alumina: 30 vol%.
 Ceria: 10 mol%.
 Alumina nanoparticles (10–100 nm) are trapped
within zirconia grains,
and zirconia nanoparticles (10 nm) are trapped
within alumina grains.

93. Microstructure of a conventional Y-TZP (left) and
a Ce-TZP/alumina nanocomposite (right).

94. Ce-TZP/A (continued)
 Excellent resistance to LTD.
 Better mechanical properties than Y-TZP.
 Highest flexural strength: about 1400 MPa.
 Highest fracture toughness: 19 MPa.m0.5.
 Reliable framework for posterior FPDs.

95. Inhibition of crack propagation by stress-induced
phase transformation.