all ceramic restoration

what is the most common dental ceramic used in dentistry

full-strength zirconia

two types of all-ceramic systems

• silicate ceramics- glass/crystalline phase

• oxide ceramics- metal oxides; no/or reduced glass phase

two types of silicate ceramics

• feldspathic ceramics

• glass ceramics

two types of oxide ceramics

• glass infiltrated

• polycrystalline: zirconium oxide ceramics

what is the most important property of all-ceramic materials

mechanical properties

castable ceramic crowns are composed of…

• dicor

• pyroceram

• biocor

the material tetrasilicic mica requires a two-step tx w…

separate holds for nucleation and crystal growth

purpose of castable glass-ceramic crown

to improve esthetics

problems w castable glass-ceramic crown

• strength

• marginal adaptation

what is the overall error that could be “clinically acceptable”

0.5%

CAD/CAM stands for

Computer Aided Design/ Computer Aided Manufacturing

CEREC stands for

CEramic REConstruction

Chairside Economical Restoration of Esthetic Ceramics

characteristics of CEREC

• quick

• esthetic

• strong

• preserve tooth structure

if there is no impression needed, what is taken instead for CEREC

photo taken in mouth

what is the latest system that can machine full crowns from highly condensed ceramic blocks

CEREC II

history of all ceramic restoration of fabrication techniques

three types of fabrication techniques

• sintering

• heating-pressing

• machining (CAD-CAM or Printing)

pressable ceramics

ceramic material is leucite-reinforced glass-ceramic and prefabricated in pre-cerammed cylinders in various shades

what two things are needed for fabrication of IPS Empress 2 restoration

• ceramic plunger

• ceramic ingot

heat-pressed glass ceramics

second generation heat-pressed ceramics contain about 65% lithium disilicate as the main crystalline phase, w about 1% porosity

the gray and black spots represent

black has low molecular weight- due to lithium

gray- glass; silica (higher molecular weight)

the XRD patterns shown in heat-pressed glass ceramics…

the lithium disilicate phase, lithium metasilicate phase and lithium ortho-phosphate phase; crystalline structure > 65% volume

the final microstructure of heat-pressed glass ceramics consists of…

highly interlocked lithium disilicate crystals, 5 microns in length and .8 microns in diameter

what specific technique is used for fabrication of the IPS Empress 2 restoration

layering technique

advantages of pressable ceramics

• esthetics

• less shrinkage after pressing

• no ceramming

disadvantages of pressable ceramics

• strength

• marginal adaptation

as opposed to metal-ceramics, all-ceramic contains a significantly greater amount of…

crystalline phase from 35% to 95 vol %

the higher level of crystallinity is responsible for an improvement in…

mechanical properties and higher opacity

CAD/CAM uses a _____________________ and ______________ to produce physical instances from 3D models (STL file formate)

uses a subtractive process (like computer numerical control milling) and additive process (3D printing)

Sielmens, CEREC systems: CAD/CAM dental restorations are milled from..

a solid block of ceramic or composite resin that closely matches the basic shade of the restored tooth; metal alloys may also be milled or digitally produced

what is subtractive manufacturing

making objects by removing of material from a bulk solid to leave a desired shape

what is zirconia

polymorphe w different atom arrangement states; monoclinic, tetragonal, cubic

zirconium dioxide can undergo phase transformation toughening from…

tetragonal → monoclinic

you want to stabilize zirconia in ___ or ____ at room temp

tetragonal or monoclinic

zirconia will undergo what arrangement at high temps (2370 C)

cubic

zirconia will undergo what arrangement at medium temperatures (1170)

tetragonal

zirconia will undergo what arrangement at room temperature

monoclinic

pure zirconium dioxide is a _____________ material that occurs in 3 forms

polymorphic

several different oxides are added to zirconia to stabilize the tetragonal and/or cubic phases such as…

magnesium oxide, yttrium oxide, calcium oxide, and cerium III oxide

what is the difference between the arrangement states of zirconia at various temperatures

size; cubic < tetragonal < monoclinic if at room temp

yttrium-oxide is added to pure zirconia to control the….

volume expansion and to stabilize it in the tetragonal phase at room temp

the tetragonal-to-monoclinic phase transformation occurs below ______ C and is accompanied by a ____% volume expansion

below 1170 C; 3-5% volume expansion

if sufficient quantities of the metastable tetragonal phase is present, an applied stress- magnified by the stress concentration at the crack tip, this can cause…

tetragonal phase to convert to monoclinic w the associated volume expansion

the phase transformation of tetragonal to monoclinic cause put the crack into compression, retarding its growth, and enhancing the…

fracture toughness

what is the mechanism called that zirconia can undergo when transitioning between tetragonal to monoclinic phase

transformation toughening

transformation toughening can significantly extend the reliability and lifetime of products made w…

yttrium-oxide stabilized tetragonal zirconia polycrystalline

the larger particles exert a crack-closing force in the _________ zone behind the crack tip, effectively resisting propagation of the crack

process zone

the energy required for the transformation of partially stabilized zirconia (PSZ) is taken from the enery, allowing the…

crack to propagate

manufacturing of zirconia purification process

in order to produce translucent monolithic zirconia restorations, company has altered the amount of…

alumina and yttria

_______________ is used to stabilize monoclinic-tetragonal transformation to form homogenous solid solutions

hafnium dioxide

what are the pressure techniques for manufacturing ceramic materials

• uni-axial

• bi-axial

• isostatic

what crystalline phase corresponds w the soft machining, sintering and heat-pressing fabrication technique

zirconia/fluorapatite- leucite glass ceramic

what crystalline phase corresponds w the heat pressing fabrication technique

leucite, lithium disilicate

what crystalline phase corresponds w the sintering fabrication tecnique

leucite

what was CAD/CAM technology originally intended for

fully sintered ceramic blocks→ it has now been expanded to partially sintered ceramic (soft machining), that are later fully tx to ensure adequate sintering

full process of CAD/CAM

dies/models → scanning → design → machining → removal/shading → sintering/stain

Y factor

3Y

Y factor and translucency

4Y ; high translucent

Y factor and translucency

5Y ; super translucent

Y factor and translucency

6Y ; ultra translucent

what arrangement of zirconia is associated w 3Y

tetragonal (>75%)

what arrangement of zirconia is associated w 4Y

hybrid ~75% tetragonal + 25% cubic

what arrangement of zirconia is associated w 5Y

cubic 50% tetragonal + 50% cubic

what is the grain size in conventional 3Y zirconia

less than .5 microns

what is the grain size in ultra-translucency 5Y zirconia

~1 micron

as you inc in Y factor what happens w grain size

size increases

as you inc in Y factors what happens w strength/toughness

strength/toughness decreases

as you inc in Y factor what happens w translucency

translucency inc

cubic zirconia is a colorless, synthetic gemstone made of…

cubic crystalline form of zirconia dioxide

toughness of dental ceramic materials

how is translucency related to Yttria content

Low transleucency: 3 mol

intermediate translucency: 4 mol

high/ultra translucency: 5-6 mol

grain boundaries and microporosity induce ____________ resulting in a loss in transmitted light

light scattering

zirconia shading methods

• external staining

• coloring by using infiltration liquids

• intrinsic color w metal oxides addition

• multi-layer chroma

anterior restorations typically use what type of zirconia

monolithic zirconia 3Y

monolithic zirconia characteristics

• two zirconias bonded to emulate the dentin-enamel relationship

• anatomically shaped core establishes strength, color, and depth

• wraparound veneers lets light pass through incisal and interproximal surfaces

flexural strength of all-ceramic restorative material

why to use zirconia

• highly biocompatible

• high compressive strength

• versatility- crown, bridge, implants

zirconia vs porcelain crowns