chemistry of dental porcelain
TRANSCRIPT
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Chapter 2
Introduction to Metal-Ceramic technology
Lin, Shih-Yun
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This chapter reinforces the value of the continued use of the metal ceramic restorations.
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration
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Ceramics
Glass
Glass ceramic
Dental ceramics
Porcelain
Dental porcelains
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Art or technology of making objects of clay and similar materials treated by firing.
Earthenware Glazed porcelain Dental restorations
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Inorganic crystalline materials that are fired at high temperature(sintered). Broad meaning
Too nonspecific to represent a particular dental product or even a particular category of nonmetallic materials
Including both products Veneer a metal substructure Comprise an entire restoration (substructure and veneer)
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Compounds that contain metallic and nonmetallic elements.
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• Weak structurally • require protection or strengthening
• Resist wear and mechanical forces • Harm to restorative materials and tooth
• Biocompatible • No break down or release elements
• Not transmit electric and thermal change • Protect sensitive pulpal and gingiva
• Withstand high temperatures • Within certain limits-no structural change
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Amorphous(noncrystalline) inorganic material in which atoms and molecule are not arranged in a regular lattice structure as they are in crystalline solids.
lattice structure
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Most are silicate family Based on silica (silicon dioxide, SiO2),
Found in nature as quartz
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Retains a noncrystalline glass phase along with a partially crystallized ceramic phase. Crystal nucleation and growth in the glass matrix is controlled Stronger and tougher than glass phase along.
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Ambiguous to apply to all types of ceramic dental products Anusavice: An inorganic compound of metallic and nonmetallic elements “formulated to produce the whole or part of a ceramic-based prosthesis.”
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Ceramic materials initially derived from a combination of kaolin, quartz, and feldspar sintered at high temperatures.
高嶺土 長石 石英
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Kaolin → Alumina
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Materials science perspective An amorphous glass matrix and at least one crystalline phase such as leucite(K2O-Al2O3-4Si)2
白榴石
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Ingredient (wt%) Early to 1800 High-fusing(wt%)
Feldspar 78 75 to 85
Quartz - 12 to 22
Alumina - ≤ 10
Kaolin 15.3 ≤ 3
Potash silicate 4.7 -
Dehydrated borax 2.0 -
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Yamamoto, acknowledging the glass matrix and complex crystalline phase
Describe metal-ceramic porcelains as “Crystallized glass”
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Composite structure of glasses, ceramics, or glass-ceramics Crystalline ceramic and glass-ceramic
Strengthen and toughen glass phase Ensure veneering materials compatible to substructure
Metallic oxides Opacity glasses and to add color
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Fusion temperature(melting range) High Medium Low fusing
Vastly different application in dentistry Other classification methods are needed
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration
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Metal-ceramic restorations All-porcelain restorations
Land’s all-porcelain jacket crowns McLean’s aluminous porcelain jacket crowns
Contemporary metal-ceramic porcelains Improved esthetics Improved strength Increased linear (CTE) Coefficient of thermal expansion
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熱膨脹係數
物體在單位溫度改變下,材料的長度改卛率。
Metal ↓
porcelain ↑
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1838
Kaolin ↓, color & translucency ↑ Enamel crown Placing dental porcelain on a platinum foil
substrate Adapted metal foil to the prepared teeth No mechanical or chemical attachment
1886
Vacuum firing Atmosphere ↓, color & translucency ↑
Aluminum oxide addition Strength ↑
1949
Bonding low-fusing feldspathic porcelain to metal using a gold-based alloy
Cast metal substructures indirectly using the lost-wax technique
Chemical bond
control addition of leucite crystals feldspathic porcelain
low coefficient of thermal expansion(CTE) raise high enough to maintain a stable bond or attachment between ceramic veneer and the underlying metal
Dr Elias Wildman
Land
1956
Brecker
Dentists Supply Company(Dentsply)
1962
Weinstein
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Land’s all-porcelain jacket crowns McLean’s aluminous porcelain jacket crowns
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Late 1800s Low-fusing feldspathic porcelain
Complete dentures and individual denture teeth Disadvantages
No chemical bond Platinum foil removed
Lack strength and toughness Structural failures
Not gain widespread popularity
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1965 Create special aluminous “core” porcelain
40%~50%(by weight) alumina Fired and veneered with thermally compatibly low-fusing body porcelain
Enamel porcelain Alumina free
Dentin porcelain 5%~10% alumina
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Elimination of kaolin Addition of alumina Vacuum firing leucite-containing component
Esthetics Strength Raise linear CTE
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Wildman 'reformulation vacuum firing metallic oxides
Proved opacity for masking Sufficient color for matching
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Vacuum firing Alumina addition to quartz
McLean and Hughes Dispersion strengthening
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Leucite crystals in the glass matrix High CTE(20 to 25x 10-6/℃) Weinstein, 1962
Mixture of 6 oxides
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration
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Fusion temperature Ultra low-fusing porcelains Contemporary classification f low-fusing porcelains
Fabrication method Crystalline phase(ie. Chemistry) Clinical application
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ceramic particles fuse together range, not discreet temperature Pyroplastic flow(slumping)熱塑性流動
Gradually undergo over several hundred degrees
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glass temperature(Tg) Solid to glass-supercooled liquid Significant increase in the ceramic’s CTE
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Ultra low-fusing porcelains Contemporary classification flow-fusing porcelains
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Denture teeth
Prefabricated pontic(trupontics)
Metal-ceramic & aluminous porcelains
Similar composition & microstructure
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Manual processing Machine processing
Layering, pressing Copy-milling
CAM Slip casting, glass infiltration
CAD/CAM
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Low-fusing ceramic porcelain
Strength Opacity Color CTE increased
Translucency Weaker
structure
Crystalline particle Glass matrix
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All-ceramic systems Alumina, fluorapatite, leucite lithium disilicate , lithium phosphate, mica, spinel, zirconia
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Clinical application Type of ceramic
Porcelain denture teeth High-fusing feldspathic porcelains (manufactured) Medium-fusing feldspathic porcelains (manufactured)
All-ceramic systems Based on alumina, feldspar, fluorapatite, leucite, lithium disilicate, lithium phosphate, mica, spinel, zirconia(heat-pressed, machined[CAM], sintered, and slip-caste)
Metal-ceramic porcelains
Low-fusing feldspathic porcelains(sintered)
Ultra low-fusing feldspathic porcelains(sintered)
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration
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Feldspar Potash feldspar Sodium feldspar
Quartz Alumina Kaolin Fritting and frits Phases of dental porcelains
leucite
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Potassium aluminum silicate
鉀長石 K2O-Al2O3-6SiO2 Potash feldspar Orthoclase
Sodium aluminum silicate
鈉長石 Na2O-Al2O3-6SiO2 Sodium feldspar Albite
Forming the glass matrix Fritting and coloring process
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Potash feldspar Sodium feldspar Lowers the fusion temperature More susceptible to pyroplastic flow
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Potassium, sodium, calcium oxieds Fluexes Increase porcelain's CTE approach the higher CTE level of metal-ceramic alloys
Increase the porcelain's CTE by breaking up oxygen cross-linking
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Too much oxygen cross-lining disrupted High-expansion dental porcelains Weaken restoration Cloddy appearance Difficult to glaze
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SiO2, Silica High fusion temperature Serve as framework Stabilizing porcelain build up at high temperatures prevent pyroplastic flow during sintering strengthens the fire porcelain
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Al2O3
Hardest and strongest oxide Naturally alumina
Water molecules, hydrated alumnia Pure alumina
Calcination process
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Al2O3-2SiO2-2H2O Hydrated aluminum silicate Initially act as binder to increase the moldability of unfired porcelain
Enables the porcelain to be carved Opaque
Very small quantities
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Glass modifiers Oxides of potassium, sodium, calcium
Opacifiers and pigments
Crystalline minerals Feldspar quartz alumina
High temperature Cold water Noncrystalline solids
Opaque, Dentin, Enamel Numerous color concentrates
Opaque and dentin color modifiers external colorants, colorless glaze
Viscosity Melting range Chemical durability Thermal expansion Resistance to recrystallization
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Feldspar(長石)
Molten glass phase
Glass matrix 75-85%
raise CTE
Incongruent melting (分熔)
interspersed cooling
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Overheating
Leucite crystals dissolve
CTE decreases, weakens the ceramic
How the porcelain being processed !
When porcelain cracking or bond failures occur...
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration
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Opaque porcelains Body porcelains Stains and glazes Optical qualities Color coding dental porcelain powders Starter or trial kits Requirements of a porcelain for bonding to metal Nondiscoloring dental porcelains Porcelain firing schedules
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Vita 3D-Master
Bleaching guide
Vitapan classical
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Ceramco 3, dentin porcelain
enamel porcelain
Dentin modifiers Mamelons, Add-on porcelains
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Porcelain margins and gingival tissues
stains
Chromascop
(Ivoclar Vivadent)
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Darker than body Removing and polishing Help select of body shades
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Wet the metal surface and establish a metal-porcelain bond Mask the color of the metal substructure Initiate development of the selected shade
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When opaque layer is fired Chemical bonds to form with oxides on the metal surface Metal-porcelain attachment is established
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insoluble oxides
Tin dioxide (SnO2)
Titanium dioxide (TiO2)
Zirconium dioxide (ZrO2)
Cerium dioxide (CeO2)
Zircon (ZrO2-SiO2)
Rubidium oxide
(Rb2O)
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Particle-size distribution Amount and color of the oxidized metal casting Light-colored surface oxides
Thin opaque layer
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Opaque porcelains Foundation for a body shade
Altered by color modifiers and other additives to simulate natural fluorescence Color modifiers
Higher percentage of metallic oxides for more saturated color
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Dentin porcelains Enamel porcelains Translucent porcelains Body modifiers
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The bulk of the crown buildup for most metal-ceramic restoration Major determinant of the shade Discouraged terms: gingival porcelain, cervical porcelain Gingival porcelain
Less translucent, more saturated with color
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Violet to gray range Illusion of translucency by virtue of their grayish or sometimes bluish hue Also as ”incisal porcelains”
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Appreciation increased Not transparent Not allow the transmission of all light Give depth and natural enamel-like translucency without altering the body shade
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Color concentrated Aid in internal color modification All body porcelains
Same basic chemical and physical properties Mix freely
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Dentin porcelains Color predominant
Enamel and translucent Color reduced
Body modifiers Color intense
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Yellow • Predominant color in most
teeth • Indium,
praseodymium(lemon) • Stable pigments
Green • Chromium oxide • Avoided in dental porcelain • Color of glass
White • Cerium dioxide • Titanium dioxide • Zirconium dioxide • Most popular
Black • Iron oxide
Gray • Platinum gray, diluting iron
oxide
Blue • Cobalt salts • Enamel shade
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Surface characterization Modification for custom shade matching or harmonizing
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Not to dilute color intensity Ensure fusion pint below maturation temperature of dentin and enamel porcelains
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Generally colorless low-fusing porcelains Considerable fluidity at high temperature Fill small surface porosities , irregularities After firing—re-create the external sheen or glossy appearance of a natural tooth
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Fluorescence Metamerism Opalescence
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An object absorbs light an one wavelength and reflects it at another wavelength
300~400nm
absorb reflect
400~450nm
Blue or bluish white
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Dentin exhibits more fluorescence than enamel Not all porcelains fluoresce In dark illuminated with fluorescent
PFM may appear dark compared to adjacent natural teeth
Rare earth oxides added mimic natural tooth Reduces metamerism
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Metamerism the change in appearance of an object under varying light sources
Metameric pair
2 objects match in color under one light but differ in color under another light PFM in daylight/ dark with UV
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Opalescence observation Light-scattering Sufficient daylight for light waves to be refracted in two ways
Low energy: blue / blue-white
High energy: orange-yellow orange-amber
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Light-scattering abilities of translucent porcelain
Major: Enamel and translucent powders Opal porcelains
Reproduce natural teeth Enamel and translucent areas of teeth are more likely to demonstrate greater than dentin
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Color code organic dyes to color code the porcelain powders
Dentin-pink, Enamel-blue Burn off on heating, not affect the shade
Color tags Without color differentiation
Difficult to track the placement of multiple shades of porcelain and internal color development until after a restoration has been fired
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Typical kit Opaque porcelain, opaque liquid, dentin and enamel porcelains
New product introduction
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Two features make low-fusing porcelains suitable for bonding to metal
High CTE(13.5 ~15.5 ×10-6/℃) Melt below the melting range of the alloy
High temperature can distort the metal and alter the fit of a restoration
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“nongreening”? Fire on silver-containing alloys without risk of discoloring the ceramic veneer Don’t buy too much!
Furnace must be urged of any residual silver contamination prior to resuming work with metal-ceramic porcelain
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1200℉→1800℉, 6 minute 100℉ per minute
649℃→982℃, 6 minute 55.5 ℃ per minute
Most manufacturers conversion100℉ as 55℃
Quickest way Multiply by 1.8, not add 32 Only calculating the rate of rise
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Terminology Differences in Low-Fusing Dental Porcelains Classification of Dental Ceramics Chemical components of dental porcelain Low-fusing porcelains for metal-ceramic restoration Summary
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Dental porcelain classification Chemical composition Low-fusing porcelains Various brans of dental porcelains differ in handling characteristics, ability to mask oxide layer, firing schedule
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