This document provides information on zirconia, including its structure, properties, applications, and manufacturing procedures. It discusses that zirconia can exist in three crystal structures (cubic, tetragonal, monoclinic) and that the addition of stabilizing oxides like yttria allows the tetragonal phase to exist at room temperature. It also summarizes that zirconia has good biocompatibility and mechanical properties like high flexural strength and fracture toughness due to transformation toughening, though its properties can degrade over time in the presence of water.
6. ⢠The main sources of zirconium are zirconate (ZrO2-SiO2,
ZrSiO4) and baddelyite (ZrO2).
⢠The zirconate is more abundant, but less pure,
requiring significant processing to get zirconia. (Picone &
Maccauro, 1999).
⢠Baddelyite contains levels of zirconia ranging from
96.5% to 98.5%,so it is a source of extreme purity in
obtaining zirconium metal and its compounds.
⢠Zirconium dioxide (ZrO2) resulting from baddelyite,
which is also known as zirconia.
7. ⢠Use of zirconia as a biomaterial (orthopedic) started in
the late sixties of last century.
⢠In the field of restorative dentistry, zirconia has been
used for root canal posts since 1989, for abutment since
1995, and for all ceramic posterior FPD's since 1998, the
first use of zirconia as a dental implant material in
humans was reported in 2004. (Coli P, Karlsson S.,2004)
9. Crystal chemistry
⢠The fluorite structure, named
after CaF2:
o cubic
o shows alternate stacking of full
and empty boxes, with anions at
every corner and a cation in the
middle of each full box .
⢠The coordination number of the
cation is eight (anions at corner
of cube) and that of the anion is
four, reflecting the stoichiometry
of two anions for each cation.
10. ⢠In oxides, the stoichiometry is A4+
O2, and CeO2,UO2,
ThO2, and PuO2 crystallize in the fluorite structure at all
temperatures.
⢠For ZrO2 , the room temperature monoclinic
(baddeleyite) structure is a distortion of the parent
structure, and high temperature transitions transform
these oxides to a tetragonal form and finally, shortly
before melting, to the cubic fluorite structure.
⢠The distortions in the monoclinic structure give the
cation a coordination number of seven.
11. Unstabilized Zirconia
⢠White crystalline oxide of zirconium.
⢠Zirconium oxide crystals are arranged in crystalline
cells (mesh) which can be categorized in three
crystallographic phases: (polymorphism)
(temp.dependent)
1. Cubic.
2. Tetragonal.
3. Monoclinic.
12. â˘Reduced mechanical
performance
â˘Reduction in the
cohesion of the ceramic
particles and density
â˘Allows a ceramic with
improved mechanical
properties to be
obtained
â˘Moderate mechanical
properties
volume
Large Small
13. ⢠These lattice transformations are martensitic, ch.by :
1. Diffusionless (i.e. involving only coordinated shifts
in lattice positions versus transport of atoms).
2. Occurring thermally implying the need for a
temperature change over a range rather than at a
speciďŹc temperature .
3. Involving a shape deformation .
14. ⢠During cooling, a T-M transformation occurs in a
temperature range from 670 to 1070°C,followed by a
volume expansion of approximately 3 to 4%.
⢠This phase transformation generates stresses that result
in Crack formation.
⢠Because the phase transitions in zirconia have large
volume changes, pure zirconia cannot be used as a high
temperature structural ceramic without Stabilization.
15. Stabilization
⢠The addition of stabilizing oxides is important because it
allows the maintenance of the tetragonal form at room
temperature. (Hannink et al., 2000).
⢠Different oxides, such as (Y2O), (CaO) or (MgO), can be
added to zirconia to stabilize it, allowing the tetragonal
form to exist at room temperature after sintering.
HOW??????
⢠These c* and t* phases are analogous to those in pure
zirconia but have dopant ions substituted on đđ4+
sites
and have a fraction of oxygen sites vacant to retain
charge neutrality
16. ⢠The addition of varying amounts of stabilizers allows
the formation of partially or fully stabilized zirconia
which, when combined with changes in processes,
may result in ceramics with exceptional properties
such as high flexural strength and fracture toughness,
high hardness, excellent chemical resistance and
good conductivity ions.
17. ⢠A fully stabilized zirconia is obtained by adding
sufficient amounts of stabilizing oxides, such as
16mol% (MgO), 16mol% of (CaO) or 8 mol% yttria
(Y2O3) and it has a cubic form.
⢠Since the partial stabilization of zirconia is
obtained with the same oxides, but in smaller
amounts (e.g. 2 mol% to 3mol% yttria), a multiphase
structure is created, which usually consists of
tetragonal and cubic zirconia majority / monoclinic
precipitated in small amounts. (Picone & Maccauro, 1999).
19. ⢠As foreseen by Garvie wide latitude was found in the
application of the zirconia t âm transformation in
ceramics, leading to development of three different
materials
1. Zirconia (dispersed phase) toughened ceramics ZTA
2.Partially stabilized zirconia PSZ (e.g. Ca-PSZ, Mg-PSZ, Y-
PSZ)
3.Tetragonal zirconia polycrystals TZP (e.g. Y-TZP, Ce-TZP)
⢠The origin and details of stabilization of the t phase differs
among these three toughened microstructures.
⢠The three materials share that stabilization of t occurs and
that toughness involves the martensitic t â m
transformation.
20. 1. Dispersion-toughened ceramics
⢠Dispersion of zirconia particles in
another matrix.
⢠These dispersion-toughened
materials, such as ZrO2-toughened
alumina (Al2O3)or ZrO2-toughend
mullite (3Al2O3¡2SiO2 )have been
termed ZTA and ZTM .
⢠Stability of the t* phase to room
temperature does not primarily
involve the use of dopants but is
controlled instead by particle size,
particle morphology and location
(intra- or intergranular).
21. ⢠In ZTA, for example, particles above a critical size will
transform to monoclinic symmetry upon cooling to room
temperature .
⢠This t âm transformation is martensitic, a useful way to
describe particle size effects has been to examine their
inďŹuence on the martensitic start (M) temperature;
essentially all t-phase stabilization can be viewed as
decreasing the Ms to below room temperature.
⢠Such investigation has suggested that the particle size
effect is likely due to difďŹculties in nucleating the
transformation, although considerations have also been
given to the possible effects of surface and strain energy
and chemical free energy driving forces .
22. ⢠porosity (between 8 to 11%)
⢠In-Ceram Zirconia
(Vita Zahnfabrik)
⢠30% glass and 70% polycrystalline
ceramic consisting of Al2O3:ZrO2 in
a vol.% ratio of approximately
70:30.
23. 2. Partially stabilized zirconia
⢠In these ceramics t-ZrO2 intra-
granular precipitates exist
within a matrix of stabilized c-
ZrO2.
⢠Stabilization involves dopant
addition, such as with CaO,
MgO and Y2O3 , in
concentrations lower than that
required for full c-ZrO2
stabilization.
⢠Precipitates are fully coherent
with the cubic lattice, forming
on a nanometer scale with
lenticular morphology
(approximately 200 nm
diameter and 75 nm thick)
parallel to the three cubic axes .
24. Mg-PSZ (magnesia partially stabilized zirconia)
⢠consists of an array of cubic zirconia partially
stabilized by 8 to 10mol% of magnesium oxide.
⢠Due to difficulty in obtaining free silica Mg-PSZ
precursors (SiO ), magnesium silicates can form a low
content of magnesia, favoring the transformation
from tetragonal to monoclinic (tâm) and resulting in
lower mechanical properties and stability of the
material.
25. ⢠porosities and large grain
size (30â60 Îźm) that may
lead to surface wear.
⢠Denzir-M, Dentronic AB,
Sweden
26. 3.Tetragonal zirconia polycrystals
TZP
Single-phase
⢠Made of 100% small
metastable tetragonal
grains (Y-TZP) after the
addition of approximately 2
to 3 mol% yttrium oxide
(Y2O3) as a stabilizing agent.
(Lindemann W.2000)
27. ⢠The fraction of the T-phase retained at room temperature
depends on:
1. the processing temperature,
2.the yttrium content,
3.the grain size,
4. the grade of constraint exerted on them by the matrix.
⢠Above a critical grain size, which is primarily related to the
yttrium oxide concentration, spontaneous T-M
transformation of the grains can take place, whereas this
transformation would be inhibited in a finely grained
structure.
28. ⢠Reduction in grain size and/or increase in concentration of
the stabilizing oxide(s) can reduce the transformation rate.
⢠To obtain a tetragonal metastable phase at room
temperature, the grain size must be less than 0.8 mm and
the amount of stabilizing oxide not more than 3 mol%.
⢠Y-TZP ceramics can be produced with the co-precipitation
of Y2O3 with ZrO2 salts or by coating of the ZrO2 grains
with Y2O3.
29. ⢠high refractive index, low
absorption coefficient and
high opacity in the visible
and infrared spectrum.
⢠DC Zirkon (DCS Precident,
Schreuder & Co)
⢠Cercon
(Dentsply Prosthetics)
⢠Lava (3M ESPE)
⢠In-Ceram YZ
(Vita Zahnfabrik)
31. Biological characteristics
1. Biocompatibility:
⢠high biocompatibility , especially when it is
completely purified of its radioactive contents.
(Gahlert et al., 2007; Andreiolli et al., 2009).
⢠Zirconia based ceramics are chemically inert
materials, allowing good cell adhesion.
32. 2. Degree of toxicity:
⢠zirconia has a lower toxicity than titanium oxide.
⢠NO cytotoxicity, carcinogenicity, mutagenic or
chromosomal alterations in fibroblasts or blood
cells. (Vagkopoulou et al., 2009).
33. 3. Radioactivity:
⢠Zirconia powder contains small amounts of
radionuclides from the uranium-radium (226Ra) and
thorium (228Th) actinide series. Concern medically
⢠However, after purifying procedures, zirconia powders
with low radioactivity (< 100 Gyh-1 ) can be achieved.
considered suitable for biomedical applications.
⢠Recommended to be validated before use for
biologic applications.
34. Mechanical characteristics
1. Flexural strength:
⢠Flexural strength is an important mechanical property
that aids in predicting the performance of fragile
materials.
⢠Strongly affected by the size of flaws and defects on the
surface of the material tested.
⢠Milling may introduce residual surface compressive
stresses that can significantly increase the resistance of
zirconia ceramics.
⢠On the other hand, severe wear can make profound
defects, which act as stress concentrating areas.
35. ⢠Alternative methods, such as the partially sintered
method of ceramics manufacturing, as well as wear-
free procedures, should be developed to obtain
crowns and bridges of the Y-TPZ system that increases
strength and reliability.
⢠Accumulation of microcracks resulting from loading in
an aqueous environment (oral cavity), can cause
surface defects that act as enhancers of tension in
areas of local concentration, facilitating the initiation
of fracture under low level applied stresses. (Lee et al.,
2000).
36. 2. Phase transformation and transformation toughening
⢠Fracture toughness indicates the material's ability
to resist rapid crack propagation. (Scherrer et al., 1998)
⢠In zirconia, During cooling, a T-M transformation
occurs in a temperature range from 670 to 1070°C.
⢠Of martensite type: -transformation without mass
transfer.
- range of temperatures.
- changes the shape of the nucleus.
37. ⢠In the presence of a small amount of stabilizing oxide
additives , the tetragonal particles provided are small
enough and can be maintained in a metastable state at
temperatures below the t m transformation
temperature.
⢠Under stresses, i.e, when a crack propagates within the
material mass, the tetragonal grains can be transformed
to monoclinic. This particular transformation is
associated with a volume expansion of 3 to 5% of the
grains, which ultimately leads to compressive stresses at
the edge of the induced crack front.
38. ⢠The enhancement in toughness is obtained, because the
energy associated with crack propagation is dissipated
both in the T-M transformation and in the overcoming
of the compressive stresses due to volume expansion.
39. 3. Toughening:
⢠The addition of alumina to zirconia Y-TZP :
presence of impurities of alumina at the edges
provides an increase in transgranular fracture mode.
⢠T-m transformation under stresses:
increase in the volume of the particle compressive
stresses on the surface of the cracks in regions close to
their terminus close the cracks.
⢠crack deflection:
crack changes its propagation direction after
encountering a particle of the second phase, pore or
grain boundaries.
40. 4. Aging (LTD):
⢠progressive and spontaneous phenomenon
results in the degradation of the mechanical
properties of Y-TZP and is exacerbated in the
presence of water, steam or fluids.
⢠Aging occurs through a slow surface
transformation to the monoclinic stable phase.
42. 2. The transformation occurs
through nucleation and growth
processes a cascade of
events occurring in
neighboring particles
increase in volume stresses
the particles subcritical
crack growth (SCG), offering a
way for water to penetrate
inside the material.
nucleation
growth
SCG
43. Three hypotheses of the low
temperature degradation
1. Diffusion of water
species (OH-) into the
lattice via oxygen
vacancies and change of
lattice parameters.
(Chevalier J 2009)
44. 2. H2O reacts with Y2O3 to
form clusters rich in Y(OH)3 .
(Lange FF, et al. 1986)
3. The water vapor attacks the
Zr-O bond, breaking it and
leading to a stress
accumulation due to
movement of -OH.
This in turn generates lattice
defects acting as nucleating
agents for the subsequent T-
M transformation. (Yoshimura M
1987)
45. to minimize the degradation of 3Y-TZP
⢠reducing the particle size.
⢠increasing the content of a stabilizing oxide.
⢠formation of composites with aluminum oxide (Al2O3).
⢠Fine polishing of the surface can reduce surface defects
created in the finishing, improving the mechanical
properties of the surface.
46. Optical characteristics
⢠adequate translucency + adequate strength .
⢠Considering the currently available ceramic materials,
these two properties cannot be obtained by a single
material.
⢠Infrastructures of zirconia provide good masking of
darkened substrates due to an adequate level of opacity,
and they also allow a controlled translucency after
lamination, due to their homogeneity and high density .
47. ⢠Opaque optical behaviorâŚ..due to:
grain size is greater than the length of light, high
refractive index, low absorption coefficient and high
opacity in the visible and infrared spectrum.
⢠Currently, colored zirconia cores are offered by some
manufacturers to enhance esthetic outcomes. Different
coloring agents are introduced for a better esthetic
performance of the white shade zirconia frameworks.
49. ⢠Clinical applications of zirconia includes:
1. veneers.
2. full and partial coverage crowns or fixed partial
dentures(FPDs)
3. posts and/or cores
4. primary double crowns
5. implants
6. implant abutments.
⢠auxiliary components :
cutting burs , surgical drills, extra-coronal attachments,
and orthodontic brackets .
50. 1.Bilayer veneers:
⢠veneered high-toughness ceramic core enhance both
esthetics and strength.
⢠due to the inherent opacity of the zirconia core(0.2 mm to
0.4 mm) , the clinical application of zirconia bilayer
veneers may offer a high-strength veneer restoration with
better masking ability for a given discoloration.
51. 2. Zirconia crowns:
⢠Tooth preparation(1.5 mm to 2.0
mm incisal or occlusal reduction and
1.2 mm to 1.5 mm axial reduction).
3. Zirconia fixed partial dentures:
⢠high flexural strength and fracture
resistance.
⢠anterior and posterior .
52. 4. Zirconia posts:
⢠translucency and tooth-colored
shade
⢠higher rigidity results in more of
root fractures than fracture of posts
⢠difficult to remove
⢠VALLPOST⢠Zirconia Posts
53. 5. Zirconia implants:
⢠Excellent esthetics as metal free
⢠Natural white color
⢠Biocompatible
⢠Better gingival health
⢠Neutral
⢠First choice in patients with
titanium allergy.
54. ⢠Commercial zirconia
implant systems currently
available are the
following:
⢠Ceraroot (Spain)
⢠Sigma (Switzerland)
⢠White Sky (Germany)
⢠Z-Systems (Germany)
⢠Zit-Z (Germany)
55. 6. Zirconia implant abutments:
⢠prefabricated and custom-made.
⢠enhanced biocompatibility, metal-
like radiopacity , reduced bacterial
adhesion, plaque accumulation,
and inflammation risk.
57. Zirconia dental auxiliary components
⢠Orthodontic brackets:
⢠enhanced strength, superior
resistance to deformation and wear,
reduced plaque adhesion, and
improved esthetics, good sliding
properties with arch wires.
⢠bond strengthâŚ.. acceptable (using
light-cured adhesives) , however,
bond failure is detected at the
bracket/adhesive interface.
⢠Commercially:
⢠COBY, YDM Corp. Tokyo Japan.
⢠Harmony-Hudson ltd. Sheffield UK.
⢠Toray-Yamura corp. Tokyo Japan.
58. ⢠Cutting and surgical
instruments:
⢠used in implantology, maxillofacial
surgery, operative dentistry, and soft
tissue trimming.
⢠optimal cutting efficiency , reduced
vibration ,resistance to chemical
corrosion.
⢠surgical instruments : scalpels, tweezers,
periosteal elevators, and depth gauges.
(ZLook3 Instruments, Z-Systems).
59. ⢠Precision attachments:
⢠wear and strength
characteristics
⢠a ball attachment for
overdentures (Biosnap, Incermed)
⢠extracoronal, cylindrical, or ball
attachment for removable partial
dentures (Proxisnap, Incermed).
64. 1. Technique of ceramic infiltration
(slip casting)
⢠InCeram Zirconia
⢠A porous infrastructure is
produced by slip-casting,
sintered, and later
infiltrated with a
lanthanum-based glass,
producing two
interpenetrating continuous
networks, one composed of
the glassy phase and the
other being the crystalline
infrastructure.
65. Fabrication technique
1. Die preparation
2. Mixing zirconia powder with water to
produce slip
3. The slip is painted onto the die
with a brush.
4. sintering
The water is removed by the capillary
action of the porous gypsum, which
packs the particles into a rigid porous
network
Porous
network
66. 5. lanthanum alumino-silicate glass is
used to fill the pores in the zirconia
core.
6. The glass becomes molten and flows into
the pores by capillary diffusion.
7. Removal of excess glass 8. Veneering with esthetic veneer
67. 2.Machined ceramics:
⢠Computer Aided Design/Computer Aided Manufacturing
(CAD/CAM) technology was introduced in dentistry by
Duret in the early 70âs .
⢠The technology was originally intended for fully sintered
ceramic blocks (hard machining), it has now been
expanded to partially sintered ceramics (soft machining),
that are later fully heat treated to ensure adequate
sintering.
68.
69. ďś Hard machining:
⢠Fully-sintered 3Y-TZP blocks are
used (presintering & hot isostatic
pressing HIP)
⢠high hardness and low machinability
⢠needs an extended milling period
compared to the soft-milling process
as well as demands the rigidity of
the cutting instruments. ( Isabelle Denry
et al.2008-Fernanado Zarone et al.2011).
⢠DC-Zirkon
⢠Denzir.
70. ďśSoft machining:
⢠Pre-sintered blanks, at the so-
called âgreen stateâ, are used
( compacting, cold isostatic pressing).
⢠a CAM milling of a framework
with enlarged dimension .
⢠The sintering of the framework is
completed at high
temperature(shrinkage 25%)
⢠Lava,
⢠Procera zirconia,
⢠IPS e.max ZirCAD
⢠Cercon.
72. ⢠InďŹltration of various metal salts at low concentrations:
- non uniform color (porosity gradients, limited diffusion depth of
coloring solutions ).
⢠Y- TZP blocks could be custom â colored:
- inďŹltration of the machined restoration at the presintered
stage -a highly porous state -with special coloring solutions to
produce work pieces of various shades.
- After drying and at the initial stage of heating of the
immersed porous presintered zirconia blocks, the acetic,
chloric and nitric ions probably vaporized and disappear on
the surface of the pores. The metal ions form an oxide layer
on the surface of the pores of zirconia blocks.
73. ⢠The ability to control the shade of the zirconia core
may eliminate the need to veneer the lingual and
gingival aspects of the connectors in difďŹcult
situations like limited interocclusal distance and the
required connector dimensions are minimally
achieved.
⢠Also, the palatal aspect of anterior crowns and FPDs
may be fabricated of the core material only in cases
like extensive vertical overlap and lack of space for
lingual veneering porcelain
75. ⢠Zirconia core is covered by veneering porcelains to
achieve suitable esthetics.
⢠The veneering of the zirconia ceramic
-a layering technique, or a press technique, or
combination of these techniques.
- Bond: mechanical interlocking and compressive stress.
⢠Chipping or lamination of the veneer material was
recorded as one of the most common complications of
zirconia restorations.(core ďŹexure , bond failure& lack of
uniform support of the veneer by the core).
77. ⢠The use of zirconia surface modiďŹcation techniques to
achieve strong bond between coping and veneering
ceramic could improve the clinical failure rates
observed.
1. Application of a silicate intermediate layer
2. vapour deposition approach
3. Application of a liner(modify the color +bond strength )
4. Sandblasting?????
79. ⢠Zirconia cores are almost unaffected by any
processing because of their high hardness and
crystallinity. (Amaral R,2008)
⢠Several studies investigated different bonding
methods as surface roughening, silica coating,
silanization and the use of different bonding agents
to zirconia ceramic.
80. micromechanical
interlocking
1. Sandblasting:
2. Hot chemical
etching
3. Laser
treatment
4. Nano-
structured
alumina coating
chemical adhesion
1. Silane coupling
agents
2. Other coupling
agents
3. Resins and resin
composites
4. Gas ďŹuorination:
chemical bonding
&
micro-mechanical
interlocking
1. Silica coating
2. Selective
inďŹltration
etching(SIE)
81. Surface treatment methods causing
micromechanical interlocking:
1. Sandblasting:
- Surface roughness the surface area, wettability
- Clean the surface substrate
- its effect on mechanical properties is controversial
2. Hot chemical etching:
-selectively etches the zirconia ceramic surface rough
surface and enhances the possibility of mechanical
interlocking with resin cements.
-The etchant used modiďŹes the grain boundaries by removing
the less arranged high energy grain boundaries.
82. 3. Laser treatment:
⢠Absorption of laser energy by zirconia ceramic
resulted in a smooth surface with irregular
microcracks .
⢠Such surface treatment was investigated and the
results were controversial.
4. Nano-structured alumina coating:
⢠application of a nano-structured alumina coating with a high
surface area and good wettability.
⢠signiďŹcantly improve the bond strength to resin cements
83. Surface treatment methods causing
chemical adhesion
1. Silane coupling agents:
⢠Used to enhance the bonding of the resin composite to HF-
etchable ceramics or silica coated oxide ceramics .
⢠Zirconia ceramics are not silica based. SO, they present a physico-
chemical challenge for reliable and durable resin bonding.
⢠2. Other coupling agents:
⢠A new primer (AZ Primer, Japan) containing a phosphonic acid
monomer promoting bonding resin cements to zirconia ceramics.
84. ⢠primers containing a phosphonic acid monomer (6-
MHPA and MDP) effective in promoting bonding of resin
cements to zirconia ceramic
85. 3. Resins and resin composites:
⢠The use of a phosphate monomer containing luting resin for
cementation of zirconia restorations provides signiďŹcantly higher
retention of zirconia ceramic crowns than conventional luting
cements and surface treatments are not necessary.
⢠RelyX Unicem
4. Gas ďŹuorination:
⢠oxyďŹuoride conversion layer was created on the surface of
zirconia ceramic and thus increase its reactivity.
⢠oxiďŹuoration conversion layer formed was effective in bonding to
silane coupling agent.
86. Surface treatment methods causing
chemical bonding &
micro-mechanical interlocking
1. Silica coating:
⢠Aims: clean the surface, create a highly retentive surface
,promote good bonding to resin cement through silane
application.
87. There are many methods used for silica coating:
1. A thermal silica coating system:
⢠Sandblasting followed by silica-coating. Then, the surface was
coated with silane which formed at increased temperature silica
coating for the substrate.
⢠(Silicoater MD system)
2. Tribochemical silica coating:
⢠the same principle with a speciďŹcally surface-modiďŹed alumina
with SiO2 coating.
⢠creating chemical bonds by applying kinetic energy in the form of
sandblasting, without additional heat or light.
88. ⢠The ďŹrst tribochemical silica-
coating system for dental use
(Rocatecâ˘system, 3 MESPE,
Seefeld, Germany)
⢠Tribochemical silica-coating using
CoJet⢠at the dental ofďŹce is a
widely used now as a
conditioning method for both
ceramic and metal alloy.
⢠Disadv: subcritical crack
propagation in thin restorations.
89. 3. Silicoater-technology:
⢠ďŹame from mixture of butane gas and
tetra ethoxysilane (TEOS)
pyrolysis of silanes
⢠Tetraethoxysilane decomposes in the
ďŹame to produce =Si-O-C= type
species , the surface will be covered
by a layer of these fragments which
bond adhesively to the substrate
surfaces.
⢠PyrosilPenâ˘
90. 2. Selective inďŹltration etching(SIE):
⢠Transform zirconia surface into a retentive one by promoting the
inter-grain nanoporosity. Such porosity will be inďŹltrated and
interlocked by the resin cements.
⢠SIE utilizes a speciďŹc glass inďŹltration agent that is capable of
diffusing between the grains and results in nano-inter-grain
porosity.
⢠thin layer of a glass conditioning agent is coated onto the zirconia
surface heated to above the glass transition temperature. The
molten glass particles may infiltrate between the surface grains
specimens are allowed to cool at room temperature. The
conditioning agent is then removed by applying hydrofluoric acid
and rinsing it off. This creates a new retentive surface for resinâ
zirconia bonding.
92. ⢠Full Zirconia is a monolithic zirconia crown, bridge,
screw-retained implant crown, inlay or onlay with no
porcelain overlay.
⢠Perfect for bruxers and grinders.
⢠these shear resistant, all-zirconia crowns are designed
and milled using CAD/CAM technology for accuracy
and predictability.
⢠With these virtually unbreakable all-ceramic crowns,
you can provide your patients the strength to
withstand severe parafunctional activity and avoid
metal restorations.
93. Technical considerations
⢠Monolithic zirconia restorations begin as chalky
white blocks. They are milled to their designed shape
and then dyed to the required shade.
⢠Staining:
- Staining is done in one of two ways
1.Monochrome tech.
2.Gradient shading.
94. 1.Monochrome tech.
⢠The restoration is
soaked in a dyeing
liquid for 2 minutes to
approximate the
desired shade .
⢠Being chalky and
porous, the restoration
absorbs the stain.
â˘
95. 2.Gradient shading.
⢠In the three-zone gradient
shading technique:
1.The unsintered restoration is
first brushed with the desired
final color around the cervical
zone of the crown.
2.The body of the the crown is
brushed with the desired body
shade.
3.Effect shades are used to
characterize the occlusal area
of the crown.
