L8 Ceramics NOTES.pdf

Dental Ceramics
D6318 Biomaterials
2011
Ceramics
1. Ceramic: any product essentially made from metallic and non-metallic minerals by firing at high
temperatures
2. Porcelain: specific type of ceramic
a. Kaolin, quartz, and feldspar mixture fired at high temperature
b. Used for denture teeth, porcelain jackets, ceramic/metal restorations (PFM), veneer ceramic
for some types of all-ceramic restorations
Application of Dental Ceramics
1. Porcelain denture teeth
2. Ceramic-metal restorations, porcelain fused to metal restorations (PFM)
3. All-ceramic restorations
a. Monoceramic (monolithic) restoration (veneer, inlay/onlay, some types of crowns)
b. Porcelain fused to ceramic (zirconia): PFZ (crowns, FPDs)
1) Bilayered restoration: coping veneered with porcelain/ceramic layer
Classification of Dental Ceramics
1. Fusion Temperature
a. High-fusing: 1300-1370C
b. Medium-fusing: 1110-1250C
c. Low-fusing: 870-1050C
d. Ultra-low-fusing:

Ceramic denture teeth
1. Disadvantages:
a. Higher fracture rate
b. No bond to PMMA denture resin base: Mechanical retention (pegs or holes in teeth)
c. More difficult to adjust
d. Abrade tooth structure and other non-ceramic restorations
2. Advantages
a. Minimal denture tooth wear with max/mand complete denture, as opposed to polymer
denture teeth.
Vertical dimension changes are related to what factors
Historical background ceramic restorations
1. 1900’s, porcelain jackets; Low strength, limited to anterior teeth
2. 1960’s, porcelain fused to metal restorations
a. Higher strength due to metal framework
b. Better match of coefficient of thermal expansion between alloy & ceramic
3. Late 1990’s all-ceramic restorations
a. Glass ceramics (monoceramic-no coping/framework)
b. Porcelain fused to alumina (ceramic coping/framework)
c. Porcelain fused to zirconia (ceramic coping/framework)
Ceramics for ceramo-metal restorations (PFM)
1. Low and ultra-low fusing ceramics
a. Melting temperature of the alloy must not be exceeded during ceramic firing process
b. Coefficient of thermal expansion (CTE) of alloy slightly greater than ceramic
c. Ultra-low fusing ceramics are less abrasive than low fusing.
1) Important consideration when ceramic restorations are used in anterior mandible and will
occlude with maxillary natural dentition.
2) In contrast, less of a problem with anterior maxillary restorations, because can have
lingual metal occluding with anterior mandibular natural dentition.
d. UMKC ceramic: Ceramco 3, Low-fusing.
2. Feldspathic dental porcelain
a. Composition: Feldspar 75-85%; Kaolin ~5%; Silica 15%; Metallic Oxides ≤ 3%
b. Powder contains glass components and crystals (leucite)
1) Metallic oxides (pigments/opaquers) added to powder
c. Sintering (Firing)
1) Used in crown/FPD fabrication process; porcelain sintered onto the metal framework
2) Powder particles sintered together to form a continuous mass
a) Glassy matrix with leucite crystals = Porcelain
3) Although porcelain is a glass matrix with crystals, it is not a true “Glass Ceramic”
a) Glass ceramic: during heating process, some glass is converted into crystal.
3. Microstructure feldspathic porcelain
a. Glassy matrix surrounding leucite crystals (10-20% crystalline)
4. Ceramic adhesion to metal
a. Chemical bonding of ceramic metallic oxides with oxides of alloy structure
b. Micro-mechanical interlock
c. Macro-mechanical interlock
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All-ceramic restorations
1. All-ceramic materials
a. Glass ceramics
1) Start with glass to form restoration and crystalline phase forms during processing (heatpressing).
a) Final material has higher crystalline percentage than dental porcelain.
2) Can be monoceramic/monolithic restoration: no separate framework, no porcelain
veneering step
3) Some too opaque and must be veneered with porcelain
b. Glass-infiltrated ceramics
1) Molten glass is infused into porous, crystalline ceramic
2) Higher crystallinity than glass ceramic
3) Serve as a framework that is veneered with porcelain
c. Glass-free, Polycrystalline ceramics
1) 100% crystalline material
2) Framework material that must be veneered with porcelain
2. All-ceramic processing techniques
a. Heat-pressed: Glass ceramics
b. Machined (CAD/CAM):
1) Glass ceramics, Glass-infiltrated ceramics, Polycrystalline (glass-free) ceramics
Current All-Ceramic Systems
1. Heat-pressed all-ceramic restoration
a. Lost-wax technique, injection molding of ceramic
b. Glass ceramics used
1) Leucite-based ceramic
a) 35-55% crystalline (higher crystalline % than feldspathic porcelain,10-20%)
b) Options:
(1) Used alone—monolithic (must be stained)
(2) Veneered with CTE compatible ceramic
c) Examples: Empress (Ivoclar); OPC (Pentron), Cerinate (DenMat)
d) Flexural strength: ~110-140 MPa
e) Applications: Anterior crowns, onlays, inlays, veneers (Single units)
Lumineers (Cerinate, www.cerinate.com)
1. Veneering system which can be fabricated so thin that tooth reduction may not be necessary.
2. 0.3-0.7 mm thick veneers, returned to the dental office etched and ready for bonding to uncut,
etched tooth structure
3. Cerinate porcelain composition is a closely guarded trade secret.
a. Apparently, contains a high proportion of leucite crystalline inclusions
b. Crystals contact each other and form a nearly contiguous internal skeleton to support and
strengthen the surrounding glass matrix
c. Microstructural examination showed leucite crystals clusters (1.5 microns) in Empress.
Cerinate porcelain exhibited a uniform distribution of fine leucite crystals (1 micron).
(Cattell et al 1997)
4. Flexural strength (MPa): Cerinate 110; Empress 135; Feldspathic porcelain 75
2) Lithium disilicate-based ceramic
a) ~60-70% crystalline: stronger, more opaque than leucite-based heat-pressed
b) Examples: IPS e.max (Ivoclar); OPC 3G (Pentron)
c) Options:
(1) Monolithic restoration
(2) Ceramic core with CTE compatible porcelain
d) Flexural strength: 350 MPa
e) Applications: Crowns and FPDs
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2. Machined all-ceramic restoration
a. Computer-aided manufacturing (CAM) (most dental applications use machining process)
Typically linked to computer-aided design (CAD), restoration design
b. Depending on the material and application, can be machined as a monolithic restoration or
as a coping/framework that is veneered with a CTE compatible porcelain
c. In-office CAD/CAM systems, such as CEREC, machined single-unit monolithic/monoceramic
restorations (not crown coping or FPD framework).
d. Only specific materials are appropriate for copings/frameworks with added porcelain layer
(bilayered restorations).
1) Zirconia is commonly used today as framework material, but must be machined with an
in-lab CAM system (not in-office)
2) *Y-TZP = Yttria stabilized-tetragonal zirconia polycrystals
3. All-ceramic materials flexural strength comparisons
Product Material Application Flexural Strength (MPa)
Coping/Framework:
Zirconia (Y-TZP)*
for crowns,
950
(Polycrystalline, Glass-free)
anterior/posterior FPDs
Lava, Cercon,
Procera AllZirkon
e.maxZirCAD
Procera AllCeram
inCoris Al (Cerec)
inCeram Zirconia
e.Max CAD
Empress
Vita Mark II
Alumina
(Polycrystalline, Glass-free)
Alumina/Zirconia
(Glass-infilitrated)
Lithium disilicate
Leucite-based
(Glass ceramic)
Feldspar-based
(Glass ceramic)
Coping/Framework:
for crowns, anterior FPDs
Coping/Framework:
for crowns, post FPDs
Coping/Framework:
for crowns, ant FPDs
OR Crowns, onlays
Restorations: Crowns,
veneers, onlays, inlays
Restorations: Crowns,
veneers, onlays, inlays
650
600
350
150
100
4. Zirconia properties
a. Zirconia = Zirconium dioxide (ZrO 2 ) Key Properties
1) High density, High wear resistance, High fracture toughness, High hardness
b. Ceramic strength differences related to differences in crystallinity. Higher crystallinity, higher
strength. Crystals inhibit crack/fracture propagation. However, with increased strength, also
increased opacity and typically requires a porcelain veneer.
c. Polycrystalline materials exhibit the highest strength. Takes more energy for the
crack/fracture to go around the crystals.
1) Although both alumina and zirconia are polycrystalline higher strength ceramics, zirconia
exhibits the highest fracture resistance, which is related to load-induced phase
transformation. Cracks that might form during loading are closed due to a load-induced
change in the crystalline structure, i.e. smaller crystals become larger with loading and
close the crack. (Rose 1987)
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5. All-ceramic, zirconia-based restoration (PFZ) considerations
a. CAD software: coping/framework is automatically designed to be 0.5 mm thick.
1) However, in situations where excess tooth structure has been lost, a 0.5 mm thick
coping/framework results in thick, unsupported veneer porcelain that is susceptible to
fracture.
2) Most systems have been modified to allow override for coping/framework design.
b. Very thin coping
c. Internal adjustments
6. All-ceramic restoration overview
a. Monoceramic/monolithic restoration (does not include high-strength core/framework)
1) VitaMark II (machined feldspar glass ceramic)
2) Empress (pressed or machined (CAD) leucite glass ceramic)
3) e.max (Press or CAD) lithium disilicate ceramic)
b. Ceramic core veneered with compatible porcelain/ceramic veneer
1) Empress (see above, can also be used as single material)
2) e.max (lithium disilicate glass ceramic)
3) InCeram (machined Glass-infilitrated ceramics)
4) AllCeram (machined Polycrystalline alumina)
5) Lava; Cercon; AllZirkon, e.maxZirCAD (machined polycrystalline zirconia)
Clinical Performance of Ceramo-metal and All-Ceramic Restorations
1. Ceramo-metal crowns and FPD (PFM)
a. High strength; less translucent due to metal coping
b. FPD survival: 96% at 5 yrs, 87% at 10 yrs; 85% at 15 yrs (Walton et al 2002)
c. Failure modes: Tooth fracture, 38%; Perio breakdown, 27%; retention loss, 13%;
caries, 11%. Small percentage, loss of veneer porcelain.
d. When less than optimal occlusal clearance, can modify coping/framework to have partial
metal occlusion.
2. All-ceramic restorations
a. More esthetic
b. Improved strength with newer systems (PFZ)
c. No long-term (>10 yrs) survival studies:
d. Crowns
1) Greatest survival with incisors
2) Decreases progressively to a maximum failure level (fracture) with 2nd molars
3) ProCera AllCeram crowns (6-year study, 60 anterior, 46 posterior crowns):
a) Survival: anterior, 96%; posterior, 91%, does not include fractured posterior crowns
repaired with composite and not replaced (Walter et al 2006)
4) Empress: 95% survival 5-10 years (Update on All-Ceramic Products, JADA supplement Sept 2008)
e. All-ceramic FPD less successful than all-ceramic crowns
1) Empress 2 (e. Max), 30-50% fracture within 2 years (Marquardt & Strub 2006; Taskonak & Sertgoz 2005)
2) InCeram Alumina, 88-90% survival, 3-5 years (vonSteyern et al 2001; Olsson et al 2003)
3) InCeram Zirconia (35%ZrO/65%AlO), 95% survival, 3 yrs (Suarez et al 2004)
4) Lava (PFZ), 100% frame work survival, 3-6 yrs (Dental Advisor 2009-Blackboard)
5) Catastrophic failure mode: fracture at connector
a) Critical factors: material strength and connector size
6) Other failures, porcelain/veneer chipping
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f. All-ceramic FPD failures
1) Posterior FPD require higher strength material
a) Occlusal forces: Anterior 150-300 N vs Posterior 400-800 N
b) Most potential for posterior FPD success: using machined polycrystalline zirconia
framework veneered with compatible ceramic (PFZ)
2) Connector size (height) very critical (height > width)
a) Measure space available from interproximal papilla to incisal edge or marginal ridge
b) Anterior: need 5 mm; Posterior: need 4-5 mm depending on material used
Material
e.Max CAD
InCeram alumina
InCeram zirconia
Procera AllCeram
Application
c) Is there adequate space for the connector Important clinical decision in treatment
planning.
(1) How do you measure the space
(2) Which dimension is more critical
3. Considerations: Zirconia-based restorations
a. Veneer porcelain chipping is a problem with PFZ restorations.
1) Initially used porcelain for PFMs; coefficient of thermal expansion mismatch resulted in
porcelain fracture
2) Porcelain reformulated, specific for ZrO-based restorations (PFZ)
3) Veneer fracture related to CAD software issues
a) Coping/framework automatically designed 0.5 mm thick.
b) Problem if thick unsupported porcelain
c) System override to design as needed
b. Porcelain veneer options for PFZ restorations
1) Powdered, sintered veneer on CAD/CAM ZrO framework
(same porcelain process as PFM)
2) Pressed ceramic veneer on ZrO framework
a) e.max ZirCAD (ZrO): CAD/CAM frame
b) e.max ZirPress: ceramic veneer pressed onto the ZrO frame
3) CAD-on veneer
a) e.max ZirCAD (ZrO): CAD/CAM framework
b) e.max CAD (lithium disilicate): CAD/CAM (machined) ceramic veneer
c) Glass sintering ‘cement’ is used to fuse the framework and the veneer together
c. Despite updates, chipping continues to be a problem with PFZ.
d. PFZ adequate occlusal clearance required
1) Occlusion on ZrO framework not recommended. Why
Connector Dimensions
Occlusal x Buccal
Total area (mm 2 )
(mm)
3-unit Anterior FPD 4-5 x 3-4 12-20
3-unit Posterior FPD
(not adequate esthetics for anterior)
3-unit Anterior FPD
(Maximum 11-mm edentulous space)
4-5 x 3-4 12-20
3 x 3 9
Lava, Cercon
3-unit
3 x 3
9
Procera AllZirkon,
4-unit (2 pontics)
4 x 3 (min)
12 (min)
e.max ZirCAD Anterior or Posterior FPD
Ceramo-metal FPD connectors: Occl/Bucc dimensions, 2.5X2.5 mm=6.25mm 2 (Raigrodski 2004; Ivoclar 2009)
2) With PFM, framework can be in occlusion, if limited occlusal clearance.
e. Full-contour zirconia restorations now available
1) No porcelain veneer (eliminate porcelain chipping problem)
2) ZrO high hardness, concern for wear of opposing dentition
3) Applications: ZrO opposing ZrO restorations; Bruxers (BruxZir Brand)
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All-ceramic crown/abutment preparation (See 3M ESPE LAVA Handout Bb)
1. Anterior: Incisal reduction: 1.5-2.0 mm; Labial/Lingual reduction: 1.0-1.5mm; Chamfer/shoulder
margin: 1.0 mm
2. Posterior: Occlusal reduction: 1.5-2.0 mm; Axial reduction: 1.0-1.5 mm; Chamfer/shoulder
margin: 1.0 mm
All-ceramic restoration cementation procedures
1. Glass and glass-infiltrated ceramics (Ex: VitaMark II, Empress, e.max, InCeram)
a. After restoration fit adjustments, clean internal surface, etch with hydrofluoric acid (HF),
rinse, and place silanating agent
1) Why use HF with these materials What’s etched
b. Conventional resin cement (shades) with dentin bond agent (DBA) (not an adhesive RC)
1) These are typically dual-cure, light-cure initially and any deeper areas will cure over time.
2) Due to restoration translucency, cements with shade options are beneficial especially for
crowns in the anterior/esthestic zone. (High bond strength not a requirement, so
adhesive RCs, which are not as esthetic, not required)
3) Example cement options:
a) Calibra/NT Prime & Bond (Dentsply)
b) Variolink II/Syntac (Ivoclar)
c) RelyX ARC/Single Bond (3M ESPE)
4) RMGI problems with causing fracture of glass/glass infiltrated ceramic restorations
c. Excess cement cleaned, then light cure
d. With lower strength materials, occlusal adjustments after cementation
1) Increased strength from bonding to tooth
2. Polycrystalline Alumina or Zirconia coping/framework restorations (most are PFZ)
(AllCeram, Lava, Cercon, AllZirkon, e.maxZirCAD)
a. After restoration fit adjustments
1) Clean internal surface with phosphoric acid (remove saliva proteins), rinse and dry
2) Dehydrate with isopropyl alcohol, air dry
3) These restorations are NOT etched with HF and silane is NOT used. Why not
b. Cement Options:
1) GI (Ketac), RMGI (RelyX)
2) Adhesive resin cement/ no DBA (Panavia, RelyX Unicem)
a) Adhesive RC will bond to AlO or ZrO.
b) RMGI not cause fracture of high strength polycrystalline coping/framework
Clinical Studies
1. 640 Lava restorations (Dental Advisor 2009-Bb)
a. 42% molars
b. 39% premolars
c. 12% anterior
d. 6% bridges
e. 1% implants
Most cemented with RelyX Unicem cement
2. 100 posterior FPDs (3- or 4-unit), 4-yr study a
(Roediger et al. 2010)
3. 15 posterior FPDs (3- or 4-unit), 51 individual units,
4-yr study b
(Schmitt et al. 2010)
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Reference materials:
Craig’s Restorative Dental Materials, 12 th ed, 2006, Ch 18 Ceramics
Blackboard Resources:
Lava All-Ceramic System Clinical Preparation, 3M ESPE
Dental Advisor 2009, 3M ESPE Lava Crowns and Bridges 6-year Clinical Performance
Objectives and Study Questions:
1. Know dental ceramic applications.
2. Understand the basic dental ceramic composition and properties.
a. For example,
1) What are the phases present in most ceramics
2) How does the percentage of each phase affect the ceramic properties
3. Be familiar with ceramo-metal porcelains that are less abrasive and situations when those
materials are more appropriate.
4. Understand the differences in crystallinity, strength, and translucency between feldspathic
porcelain, glass ceramics, glass-infiltrated ceramics, and polycrystalline ceramics.
5. Understand the importance of the coefficient of thermal expansion (CTE) for porcelain-fused to
metal (PFM) restorations and porcelain-fused to zirconia restorations (PFZ).
6. Have a basic understanding of the different fabrication techniques for all-ceramic restorations.
7. Compare flexural strength of materials used for PFM and various types of all-ceramic
restorations.
8. Be able to identify which current all-ceramic materials appear to be most appropriate for various
applications.
a. Understand the difference between a monoceramic/monolithic restoration (no porcelain
veneer) and an all-ceramic restoration with a ceramic framework that must be veneered with
porcelain.
b. What materials are appropriate for Single crowns vs FPD applications
c. Which material appears to be most appropriate for posterior FPD use
d. What are common complications associated with all-ceramic restorations
1) Understand why despite using high strength zirconia as a coping or framework for allceramic
crowns or FPDs, the CAD-CAM restorations can be susceptible to veneer
ceramic fracture.
9. Discuss advantages and disadvantages of ceramo-metal versus all-ceramic FPDs.
a. What are differences related to occlusal clearance between preparation and opposing
dentition and restoration occlusion for PFM and PFZ
b. Zirconia restorations with no porcelain veneer are now available. What potential problem
could occur when these restorations oppose natural dentition or other non-zirconia
materials Why For what applications could these restorations be considered
c. Besides using high strength material, what is the most critical fabrication factor for allceramic
FPD success How does this differ from a ceramo-metal FPD How is this factor
evaluated
10. Be familiar with cements and procedures for the different types of all-ceramic materials.
a. Which materials should be etched with hydrofluoric acid (HF) and silanated
1) Understand what component can be etched.
b. Which materials are not HF etched and why not
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