Ceramic Restorations Flashcards
Ceramics: Applications
(5)
-All-ceramic crowns, inlays, onlays,
veneers, FPDs
-Metal-ceramic crowns and FPDs
-Implant abutments (and implants)
-Denture teeth
-Ceramic orthodontic brackets
Ceramics: Benefits
(3)
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 the ceramic
Ceramics: Benefits
Physiologic —
response when properly
contoured and highly
glazed/polished.
gingival
Why and How does ceramic look so much like a real tooth?
(3)
-Color Replication
-Refraction
-Translucency
-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)
Flexural Strength – ceramics are brittle!
-Defined as the strength of a material in bending
-Stress on the outermost fibers of a bent test specimen, at failure
Fracture Toughness
-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
Ceramics — as they are fired
shrink
Thermal insulator
(2)
–poor conductor of heat
-Coefficient of thermal expansion (CTE) is low. Does not expand and contract
much with heat and cold.
Ceramics are brittle
Griffith flaws
-A.A. Griffith (1921) suggested that the low fracture strength of glass is
due to the presence of
microscopic flaws in the bulk material. Surface
flaws act as stress initiators and cause widening and propagation of
microcracks through the ceramic material.
Griffith flaws
-A.A. Griffith (1921) suggested that the low fracture strength of glass is
due to the presence of microscopic flaws in the bulk material. Surface
flaws act as stress initiators and cause widening and propagation of
microcracks through the ceramic material.
-Porosities in the porcelain propagate —
-Damage from
-These porosities can be
cracks
grinding, heat propagate cracks
external or within the material
Crack propagation
(why ceramics fail at lower than
expected stress)
-Crack will propagate through material, or until a particle
is met which stops the crack growth.
Stress Corrosion
-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).
Sintering:
(4)
-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.
Glass Transition Temperature: (Tg)
(4)
-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.
Heat Pressing:
-Relies on
-Restoration is made from
-Also known as
external pressure to sinter and shape the ceramic at high temperature
a Wax pattern (lost wax technique)
High Temperature Injection Molding
CAD/CAM
(2)
-Computer Aided Design
-Computer Aided Manufacture
Hard Milling
(2)
-Already densely sintered material
-Silicate, glass ceramics, resin-based
ceramics
-Soft Milling
(3)
-Partially sintered material
-Zirconia and Lithium Disilicate (e.Max)
-Sintering to be completed in oven AFTER
manufacture
— are used for the milling process
Blocks
n the past, there have been limited shade selections. However,
newer multishade blocks have improved esthetics
-Also a stain and glaze done with a furnace can improve
esthetics.
Types of blocks available:
(3)
Glass Ceramics:
Zirconia:
Resin-ceramics:
skipped
Glass Ceramics:
Vita Mark 2, IPS Emax CAD, Celtra Duo Ultra
skipped
Zirconia:
IPS Emax ZirCAD, 3M Chairside Zirconia, CEREC Zirconia
skipped
Resin-ceramics:
Cerasmart, Vita Enamic
Resin: Telio blocks
skipped
CAD/CAM systems:
Itero, E4D, Trios, Planmeca, Carestream.
-More systems come on the market each year.
Predominately Glass (veneers)
(4)
-Most translucent optical properties
-Weakest material
-Feldspathic porcelain
-Can ETCH
Particle filled Glass Ceramic (eMax)
(4)
-Less translucency
-increased strength
-Lithium Disilicate
-Can ETCH
Polycrystalline Ceramic (zirconia)
(4)
-Low translucency
-Highest strength
-Alumina, Zirconia
-Cannot ETCH
Resin bonding
(3)
-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
Reinforcement of the crystalline structure
of the ceramic
(2)
-Dispersed Crystalline phase – Higher strength
and fracture resistance
-Lithium Disilicate
Transformation Toughening
(3)
-Stress induced transformation
-Unique to zirconia
-Compressive forces at crack tip retard
crack propagation
How again does porcelain break?
(2)
-Flexure
-Improper loading (askew occlusion)
Resin bonding is a high strength cementation procedure, so
bonding ceramics will — the ability of the ceramic to
flex. Therefore, — strength.
decrease
adds
Resin Bonding
-Resin bonding–etchable glass ceramics
—-% increase in glass ceramic crown strength
(4) components
50
HF Etched ceramic surface (retention)
Silane coupling agent (bifunctional monomers form a
chemical bond)
Resin Composite Cement
Etched enamel / dentin –adhesive layer
How the resin cement have so much
strength:
(2)
-The movement of the cement into the
dentin tubules forming microtags and
into the porcelain spaces (above).
This forms a matrix that has great
retention.
Veneers
-Very thin “sheet” of porcelain as thin as
— mm (minimal thickness)
-Tooth preparation is specific and is
aimed at providing
-Veneers are not under
-These are — bonded to enamel
-Can be the most — dental restoration possible
-Can be so thin, underlying tooth color
can affect — properties.
-Most technically — to fabricate
0.3 to 0.5
aesthetics and
physical support for the veneer.
heavy occlusal loads.
resin
esthetic
optical
difficult
Crystalline Reinforcement
-By adding crystalline aspects to the
ceramic, crack propagation is much
more difficult.
Small cracks begin, but
then have a harder time causing
catastrophic failure.
-Enamel flexural strength is around — MPa
-Feldspathic Porcelain flexural strength is much
lower at — MPa
300
60-70
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)!
Material only used for Veneers
Feldspathic Porcelain
-Enamel flexural strength is around 300 Mpa
-Leucite reinforced ceramic flexural strength
is — MPa
120-160
Leucite reinforced Ceramic (Empress)
Would you use this material on a posterior
tooth?
-Crown –
-Onlay/Inlay –
No
maybe (only where
occlusal force is low)
Leucite reinforced Ceramic (Empress)
-Would Resin bonding help strengthen this
material?
-Yes. It can be etched and
therefore retention and strength is
increased with resin bonding
Leucite reinforced Ceramic (Empress)
-Indications –
anterior crowns, veneers
Flexural strength for e.Max is
360-500 Mpa
-Finally stronger than enamel alone!
Due to its increased strength, Lithium Disilicate
is used for:
(4)
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)
-Should you use e.Max for a posterior three
unit bridge?
-Not Indicated
-Increased fracture of material
Zirconia has a — structure
-This provides — strength
-This provides a surface that is not
abrasive like porcelain, but
instead is
Polycrystalline
increased
gentle on opposing
dentition
Resin Bonding will not increase the
— of Zirconia
-Resin bonding will do what for
zirconia?
—-!
strength
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 — is needed for increased bonding
of Zirconia with resin cement
bonding primer
Original Zirconia crown was from Glidewell
Lab 10 years ago.
-3Y zirconia crown called —
-Horrible – aesthetic early on
-Poorly defined – anatomy
Bruxir
translucency
occlusal
3Y Bruxir flexural strength around — Mpa
1200
Ceramics: Zirconia
-Because of its —, any cement can
be used.
-Crown has to be
toughness
”fired” and will shrink to fit.
Shrinks about 25% during firing.
-How are zirconia crowns so strong:
-Transformational Toughening
(4)
-Stress induced transformation
-Unique to zirconia
-Compressive forces at crack
tip retard crack propogation
Crack initiated; tensile stress at crack tip causes
tetragonal→— shape change
monoclinic
Volume increase with associated compressive
stresses in vicinity of crack tip leading to
crack closure
Phase transformation from tetragonal (T) to monoclinic (M)
has associated volume increase (3-5%) →
high internal
stresses.
Making Zirconia more translucent:
(4)
-Adding more Yttria increases
translucency
-This results in decreased strength
-ITS IMPORTANT TO ASK YOUR LAB
WHAT KIND OF ZIRCONIA
YOU ARE USING!!!
Ceramics: Zirconia-Improving on original zirconia
-To improve esthetics,
a zirconia core is
used and then porcelain is fused
to create the tooth shape and
color.
A — is a porcelain fused to
Zirconia.
PFZ crown
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, they were not likely
to be strong
Ceramics: Zirconia
-Failures?
PFZ crowns initially had failures
Mostly in the
posterior
Zirconia would not fail (very rare), it would be the — that would fracture.
porcelain
Zirconia would not fail (very rare), it would be the porcelain that would fracture.
(3)
-Lack of porcelain support in zirconia substructure
-Occlusion, Occlusion, Occlusion
-The bond between the Zirconia and the porcelain would not be able to overcome the
difference in Coefficient of Thermal Expansion between the Zirconia core and the veneering
porcelain
Ceramics: Zirconia
-Additional benefits
With some dark teeth, a zirconia core
PFZ crown can be used to
mask dark
dentin
Ceramics: Zirconia
-Additional benefits
-Because Zirconia is not brittle, any —
technique can be used.
-Zirconia copings can be as thin as —
because Zirconia is strong
-A monolithic zirconia crown preparation can be
very — similar to gold or pfm crown
preparations
-Zirconia is friendly to opposing teeth. It is
considered —
-Can use — finish lines for
preparations
-Zirconia masks dark — and is beginning to
balance that masking with translucency
cement
0.4mm
conservative
“Wear Friendly”.
chamfer or shoulder
dentin
-If Zirconia is the Superman of crown material, what’s Zirconia’s kryptonite?
-Zirconia’s use is now very —. Its only really 10 years old in the market.
While its strength is high, that strength is compromised to make it
aesthetic. What’s the sweet spot for this balance?
heavy
If you want the most esthetic anterior restoration, what material would you choose?
- Veneer –
-Crown –
Feldspathic Porcelain
e.Max or Empress
If you want the most esthetic posterior restoration, what material would you
choose?
-Crown –
-Crown -
e.Max
5Y Zirconia
If you have a bruxing patient, what posterior restoration material would you use?
-Crown –
-Crown –
3Y Zirconia
Gold
Ceramics: Comparison: Occlusion
Anterior Teeth
(2)
-Lower occlusal forces – Less strength requirement – higher esthetic requirement
-Feldpathic Porcelain veneer resin bonded are still the most realistic tooth
restoration
Ceramics: Comparison: Occlusion
Posterior teeth
(2)
-Higher occlusal forces – higher strength requirement – less esthetic requirement
-What does the patient present with? Not a grinder – e.Max or Zirconia
Ceramics: Comparison: Occlusion
Bruxer/Clencher and needs a bridge?
(3)
-fully veneered porcelain not a great option
-Recommend monolithic zirconia or PFM.
-Possible monolithic material with buccal porcelain.
Ceramics: Comparison: Occlusion
Ceramic wear on opposing teeth
(4)
-Be aware of this side affect of ceramics!!
-Ceramics with glass wear opposing teeth.
-Zirconia less so
-Gold and metal occlusal least amount of wear.
Glass Ceramic Veneers
-Only adjust after
-Use
-Polish with
- — surface should not be adjusted if at all possible
seated and bonded with resin cement (too fragile to
adjust outside the mouth predictably.
fine diamonds with a little water
diamond impregnated polishing paste
Internal
e.Max (Lithium Disilicate)
(4)
-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
Zirconia
(4)
-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!
Ceramics: Adjusting
-After adjustment with bur is done:
(3)
-Course polisher
-Fine polisher
-Felt wheel or brush with fine diamond polishing paste
Resin Cements
-Requires — free environment
-Required for
-Requires — for etched
ceramics
moisture
low strength ceramics
silane coupling agent
Primer containing MDP
(methacryloyloxydecyl dihydrogen
phosphate) placed on zirconia can
enhance the
chemical bond to cements
containing resin.
Resin Modified Glass Ionomer
-Contraindicated in
-Acceptable for —
low strength ceramics
-Water absorption with setting of cement
leading to slight expansion and
possible fracture of ceramic at thin
margin area
Zirconia
