metal-ceramic and dental ceramics restorations

definition of ceramics

an inorganic compound w nonmetallic properties composed of metallic and nonmetallic elements

what are some examples of metallic and nonmetallic elements in ceramics

Al₂O₃ (alumina), SiO₂ (silica), SiC (silicon carbide), TiN (titanium nitride)

ceramic components and how they are joined

compounds, metallic and nonmetallic elements are joined by covalent and ionic bonds → crystalline structure

did ceramics have a higher or low conductivity, stability, and fusing temp

conductivity: low

stability: high

fusing temp: high

do metals and alloys have a higher or low conductivity, stability, and fusing temp

conductivity: high

stability: low

fusing temp: low

do ceramics or metals/alloys have a higher tensile strength

metal and alloys

true or false: ceramic materials have high surface hardness

true

true or false: ceramic materials have high compressive strength

true

true or false: ceramic materials have low modulus of elasticity

false

historical perspective of dental ceramics

dental porcelain definition

refers to specific compositional range of ceramic materials made by mixing kaolin, quartz, and feldspar, and fused at high temperature to form enamel like substance

decorative porcelain, a white translucent stoneware, was first developed in…

Jingdezhen, Jiangxi province, China circa 1000 A.D.

ceramic materials were the first material to be the subject of…

laboratory research (circo 1700 A.D.)

porcelain was the first material to be…

artificially made by man and used in dentistry in the late 1700s

De Chemant obtained French and English _________ for his formulation of dental porcelain in 1791

patents

who developed a practical formulation of porcelain denture teeth

Alexis Duchateau, a pharmacist, and Nicholas de Chemant, a dentist

Charles H Land, a detroit dentist, fused porcelain to a thin platinum foil in 1886, this developed into what in 1903

low-fusing porcelain and introduced porcelain jacket crown

evolution of dental ceramics pic

what are the 4 classifications for dental ceramics

1. fusing temp

2. application

3. fabrication technique

4. crystalline phase

do metal or ceramic have a higher melting temp, why

ceramic bc of the covalent bond

ultra low fusing temp

<850 C

low fusing temp

850-1100 C

medium fusing temp

1100-1300 C

high fusing temp

>/= 1300 C

what is the difference between these two crowns

1 porcelain crown w an inner metal lining

2 all ceramic crown w no metal lining

porcelain veneer application

different indirect restorative applications

what are the three types of the fabrication technique

1. sintering

2. heat pressing

3. machining (CAD-CAM or printing)

regardless of applications or fabrication technique, after firing, dental porcelains and ceramics are composed of at least what 2 phases

leucite crystal: ordered arrangement- strong

glass matrix- no structure

what are the four types of the crystalline phases

1. feldspar-based, sintering

2. leucite-reinforced, pressable

3. lithium disilicate, pressable

4. zirconia-based, machinable

what is the crystalline percentage of feldspars

>/= 35 volume%

what is the crystalline percentage of leucite

>/= 35 volume% Empress 1

what is the crystalline percentage of lithium disilicate

>/= 65 volume%

what is the crystalline percentage of zirconia

>/= 95 volume %

of the two types of all-ceramic systems, which is silica based and which is non-silica based

• silicate ceramics- silica based

• oxide ceramics- nonsilica-based

what are the types of ceramics that fall under silicate ceramics (2)

• feldspatic ceramics

• glass ceramics

what are the types of ceramics that fall under oxide ceramics- no or reduced glass phase

• glass infiltrated

• polycrystalline

what do you etch Feldspathic porcelain ceramic with

9.5% hydrofluoric acid gel for at least 1 min

what are the two over-arching types of ceramic restorations

• metal-ceramic restoration

• all ceramic restoration

what are the three types of metal-ceramic restorations

• porcelain-fused to metal (PFM)

• ceramometal restoration

• metal-ceramic restoration

when referring to porcelain-fused to metal, what are the melting temperature and thermal expansion properties of the alloy and ceramic before bonding (high/low for each)

melting temp for alloy: low

melting temp for ceramic: high

thermal expansion for alloy: high

thermal expansion for ceramic: low

history of porcelain-fused to metal restorations

when heat treated, these produce high expansion ceramics suitable for metal bonding

when referring to porcelain-fused to metal, what are the melting temperature and thermal expansion properties of the alloy and ceramic after bonding (high/low for each)

melting temp for alloy: high

melting temp for ceramic: low

thermal expansion for alloy: high

thermal expansion for ceramic: low

the properties of ceramics are customized for dental applications by precise…

control of the type and number of components (kaolin, quartz, feldspar) used in their production

dental porcelain fuses at a relative _________(high/low) temperature to form a hard substance much like enamel in appearance

relatively low temp

___________ is accomplished w various colored fusible materials

staining

what are the three triaxial porcelain compositions

• quartz

• kaolin (clay)

• feldspar

what is quartz

silica (SiO₂)

what is kaolin (clay)

a hydrated aluminosilicate

what is feldspar

a mixture of K and Na aluminosilicates

feldspar is a ______ (high/low) fusing component

low- 125-1170 C

what is the funx of quartz

binder

what is the funx of kaolin

opacifier and viscosity control

what is the funx of feldspar

strength and binder

what is the shape of quartz

tetrahedral shape

the addition of alkali (Na₂O, K₂O) and flux (B₂O₃) combined w crystalline silica forms a…

low fusing glass

what are glass modifiers

alkali ions: Na, K, Ca

if the tetrahedra is not aligned…

will be disorders → amorphous glass → weaker bonds → lower melting point

when adding glass modifiers to crystalline silica, you get…

sodium silicate glass

how do properties change when glass modifiers as added to crystalline silica to form sodium silicate glass

• lowers fusing temp

• inc thermal expansion

• dec viscosity

what does feldspar melt at

~1150 C

feldspar can form…

leucite and molten glass

composition of porcelains

red box: major composition

green box: feldspathic material

the feldspars are colorless, thus _______ and ________ are added for color

pigments and opacifiers

how are pigments made

• grinding together metallic oxides w feldspar and glass

• fusing the mixture in the furnace

• regrinding to a fine powder

what is the manufacturing process (generally) to form dental porcelain (frit)

1. feldspar + alumina + silica + opacifiers + pigments

2. heat treated in furnace (allows leucite crystal growth)

3. quenching

4. grind pigments to powder

5. frit

what is the processing portion of dental porcelain

• shade selection

• porcelain powders are mixed w water to produce a plastic mass of material which can be molded and carved before firing

in the processing phase of metal-ceramic restoration, what do you apply w a brush

• apply opaque w brush to oxidized alloy

• apply body and enamel w brush to opaquing alloy

• apply incisal or enamel over body porcelain

what are important opacifying oxides for dental ceramics

TiO₂ and SnO₂

when processing there is a 13% oversize to accomodate for what

shrinkage

in processing, the technician fuses the porcelain powder and simply…

remelts the drits w/o causing any significant inc in rxn between components

what is the fusion process known as

sintering

what is sintering

the outer layers of the grains of porcelain partly combine together; the process of heating closely -packed particles to achieve inter-particle bonding

sintering image

ceramic has a _________ (high/low) compressive strength and a _______ (high/low) tensile strength

high compressive and low tensile

what is glazing

a low-fusing, transparent glass that may be used as a glaze material; glaze give a crown an impervious, smooth surface and imparts greater translucency

requirements for a metal-ceramic system: the veneering porcelain must have a _____ fusing temp

low fusing temp

requirements for a metal-ceramic system: melting range of the alloy must be at least _____ higher than the firing range of the veneering porcelain

100 C

requirements for a mental-ceramic system: the alloy should have excellent _________

castability

requirements for a metal-ceramic system: the alloy substrate has adequate __________ and ______________

adequate stiffness and strength

requirements for a metal-ceramic system: the porcelain must wet the alloy surface readily during…

firing

requirements for a metal-ceramic system: coefficients of thermal expansion of the metal is slightly ______ (higher/lower) than that of porcelain

slightly higher

requirements for a mental-ceramic system: a stronger bond between the __________ and __________ is essential

between veneering porcelain and metal substrate

what are the three methods of bonding porcelain to metal

• chemical

• thermal contraction

• mechanical

bond strength of gold alloy w. vs w/o minor element added

higher w added minor elements

in obtaining surface oxide, you introduce base metal elements into precious metal alloys to form…

thin oxide

in obtaining surface oxide, direct oxide production the constituents of the alloy such as…

base metal alloys

in obtaining surface oxide, surface coating of metals w oxidizable metals such as…

In and Sn

advantages of metal-ceramic restorations

• adequate marginal integrity

• predictable strength

disadvantages of metal-ceramic restorations

• compromised esthetic results

• potential biocompatibility problem w some base-metal alloys