DENTAL CERAMICS

INTRODUCTION

• A quote a 10th century European reflecting on the porcelain

• "A ceramic so white that it was comparable only to snow, so 

strong that vessels needed walls only 2-3 mm thick and 

consequently light could shine through it. So continuous was 

the internal structure that a dish, if lightly struck would ring 

like a bell.

This is porcelain!"

Derived from:

the Greek word ‘keramos’ meaning ‘potter’s clay’/ burnt stuff.

covers various materials

• hard, 

• brittle, 

• non metallic, 

• heat-resistant and 

• corrosion-resistant.

Definition of ceramics: GPT-8

• Ceramics 

1: Compounds of one or more metals with a nonmetallic 

element, usually oxygen. They are formed of 

chemical and biochemical stable substances that are 

strong, hard, brittle, and inert non-conductors of

thermal and electrical energy.

2: The art of making porcelain dental restorations.

Made by:

• Shaping and then firing a nonmetallic 

neral, such as clay, at a high temprature.

• The non metallic minerals:

alunum oxide (alumina) and 

silicone dioxide (silica).

Two Basic Components:

• Refractory nn-meltable skletal structure sinered (fused) particles of a metallic oxide (aluinum oxide).

• Glass

infiltated between the sintered refractory partics.

mass of individual particles loosely held together by a

ater binder Called Sitering cohrent solid

the oints at which the individual particles are 

in ctact fuse at sufficiently high tempertemperatures. 

• Sintering appears to happen not so much because of melting, ut because of diffusion of the rapidly moving atoms etween 

e neighboring refractory particles.

• Diffusion is accelerated at elevated temperatures.

Difference between ceramics and porcelain

• Dental porcelain belongs to one class of ceramics

• Consists of a glass and a crystalline phase

( glas-crystal composite)

• Other ceramics are composed entirely of crystalline oxides that are siered together, sometimes under high pressure.

• Ceramic : A compound of metals such as (aluminum,alcium, lithium, magnesium) and nonmetals Silicon,

 ron, flourine and oxygen) that may be used as a single

stuctural components like CAD/CAM inlay or in

sevral layers like fabrication of ceramic based

proshesis.

Porcelain : refers to a family of ceramic

materals composed essentially of kaolin, quartz,

and fedspar, also fired at high temperature.

All porcelain and glass ceramics are

ceramicsbut not all ceramic are porcelain

or glass eramics.

Dental porcelain:

Kaolin omitted; feldspar  transluce➡ y.

Hence considered as a feldspathic glass with crystalline 

inclusions of silica.

Why use ceramics…?

•iocompatibility

• Aesthetics

• Durability

The biocompatabi

lity issue is essential to prevent adverse 

reactions within the patients.

The use of dentally coloured glasses can provide replacement 

structures that ca e made to imitate tooth structure in both 

colour, translucency and response to different lighting sources.

Improvements in fracture toughness, wear resistance, 

machinability, solubility and flexural strengthstrength. 

• Dental ceramics is a synthetic replacement material for

missing tooth a ilable in extensive range of shades and

translucencies f achieving life-like results.

• However, its esthetic appearance was compromised when it

was fused to a met substrate in an effort to strengthen

porcelain (due to t relatively low tensile strength and

brittleness of porce in ).

Shortcomings

• excessive brittleness,

• crack propagation,

• low tensile strength,

• fracture of the restoration,

• wear of antagonists and

• sintering shrinkage.

• Recent developments have attempted to over come the

principal disadvantages of inherent brittleness and potential to

abrade the opposing dentitionby either the use of

increasingly complex technolo or by the simplification of

existing techniques and/or materials.

• During the past decade severa

 new ceramic materials

and techniques have been developd like shrink-free

core materials, castable glass ceamics, porcelain

veneers, acid etched porcelain inlys onlays, se eral

novel methods of providing a metal ubstructure

without casting etc.

CLASSIFICATION OF DENTAL PORCELAIN

1. According to their Firg Temperature

• High fusing 1300C (2372F)

• Medium fusing 1101 – 1300°C (201° – 2072 F)

• Low fusing 850 – 1°00C (1962 – 2°2F)

• Ultra-low fusing <85°C (1562F)°°°

• The medium-fusing and high-fusing types are used for

the production of denture teeth.

• Thelow-fusing and ultra–low fusing porcelains are used

for crown and bridge construction

• Someof the ultra-low fusing porcelains are used for

titanium and titanium alloys

• (low-contration coefficients that closely match those of

the metals reduced risk for growth of the meal oxide)

2. According to Application

• Porcelain for artificial teeth

• Jacket crown veneer and inlay porcelain 

• Metal ceramics

• Anterior bridge porcelainporcelain

3. According to Processing Method

A. Sintered porcelain (Conventional)

B. Cast Porcelain 

C. Hot-pressed

D. Machined Porcelain

CAD-CAM 

Copy Milling

E. Slip Cast (Infiltrated)

F. Injection molded CeramicsCeramics

Sintering is a method for makiCeramics

ts from powder, by heating the material 

(below its melting point) until its paicles adhere to each other 

The base-material for 

heating ceramic .

on:

- metal coping

- planum foil

- investment material made castcast

Conventional Powder – Slurry Ceramics : using condensing &

sintering.

(a) Alumina reinforced Porcelain e.g. : Hi-Ceram

(b) Magnesia reinforced Porcelain e.g.: Magnesia cores

(c) Leucite reinforced (High strength porcelain)

e.g. : Optec HSP

(d) Zirconia whisker – fibrereinforced e.g.:MirageII

(Myron Int)

(e) Low fusing ceramics (LFC): (i) ydrothermal LFC

e.g.: Duceram LFC :

(ii) Finesse (Ceramco Inc)

Building full-ceramic works (i.e. inlays, shells, 

4. According to the Method of Firing

• Air fired i.e. at atmospheric pressure 

• Vacuum fired i.e. at reduced pressure.

5. According to the Use/Indication

• Anterior

• Posterior

• Crowns

• Veneers

• Post & cores

• FDPs

• Stain

• GlazeGlaze

6. According to the Composition

• Feldspathic porcelain

• Leucite-reinforced porcelain

• Aluminous porcelain

• Pure Alumina

• Pure Zirconia

• Glass-infiltrated Spinel

• Glass-infiltrated Zirconia

• Silica Glass

• Lithia based Glass CeramicsCeramics

7. According to the Microstructure

• Glass

• Crystalline

• Crystal containing GlassGlass

8. According to the Translucency

• Opaque

• Translucent

• TranspTransparent

• Ceramics are non-metallic, Inorganic,

rimarily oxygen ompounds with 1 or more

mtallic or semi-metallic e ements

• Ceramics composed of single element are rare

• Diamond structure is a major ceramic of this

type

COMPOSITION

• Unit cell consists of Carbon atoms each one

sharin an electr ns with each of 4 surrounding

C atoms• Structure is bonded by strong covalent forces

resultingin high elastic modulus, temperature

stability n oxygen free environment (upto

37000C) andthe highest hardnesshardness

Typical composition

• Glass matrix

• Fluxes

• Glass modifiers

• Glaze

• PigmentsPigments

• Feldspar - 60 to 80% - Basic glass former

• Kaolin - 3 to 5% - binder

• Quartz - 15 to 25% - Filler

• Alumina - 8 to 20% - Glass former and flux

• Oxides of - 9 to 15% - Fluxes (glass modifiers) 

Na, & Ca

• Metallic pigments - <1 - Color matching

ROLE OF EACH INGREDIENT 

Feldspar/Potassium Aluminosilicate 

(K2O.Al2. 6SiO2

)

• Naturly occurring mineral 

• Double silicate of K and Al

• Acts as a flux matrix and high surface glaze

• Mixing & firing with metal oxides at high temperatures forms 

glass p ase capble of softening and flow slightly 

Kaolin (Al2O3

.2

iO2

.2H2O)

• Hdrated luminium silicate

• White clay like material

• Acts as a binder & gives opacity to the mass 

Silica

• Silica acts as

 a refractory skeleton and provides strength and 

hardness to porcel in ding fusingfusing

Aluminium Oxide

• Strength and opacity 

• Alters softening point and increase the viscosity of porcelain 

during fi ing

Fluxesnd Glass Modifi

ers

• Lowers fusion temperature and increase flow of porcelain during 

firing 

• Remove impuries 

However, if concentrationf flux is too high:

• Reduces chemical durability of the glass

• Causes the glass to crystallizecrystallize

Coloring Frits

• Produced by fusing various metallic oxides with fine

glass and feldspar nd then grinding to powder

• Added to dental porcelains to obtain various shades to

match natural tooth lor

Other Additions

• Zircnium, titanium or tin oxide may be added to

provide color, opacityopacity

PROPERTIES OF PFM

Strength

• Good flexural strength (ZrO2

similar to steel)

•Glazed porcelain (141.1 MPa) is stronger than ground

porcelain (75.8 MPa) Compressive Strength (331 MPa)

• Tensile strength is low (34 MPa)

• Shear strength is low (110 Mpa) and is due to the lack of

ductility caused by the mplex structure of porcelain

• Fracture toughnesstoughness

FACTORS AFFECTING STRENGTH

• Composition

• Surface integrity, surface imperfections like 

microscopic cracksnd porosities 

• Firing procedure, inadequate firing and over firingPROPERTIES OF PFM

Modul

us of Elasticity

• Porcelain has high stiffness (69 GPa)

Surface Hardness

• Porcela

in is much harder (460 KHN) than natural teeth,

can wear natural teeth

WearResistance

• More resist

ant to wear than natural teeth

Thermal Properties

• Porcelain 

has low thermal conductivity

• Coefficient of thermal expansion (6.4 to7.8x10-6

/

0C). It is

close to that of natra teeth teeth

Specific Gravity

• The true specific gravity of porcelain is 2.242.

• Specific gravity of fired porcelain is less (2.2 to 2.3),

because of the presence of air oids.

Chemical Stability

• It is insolu

ble and impermeable to oral fluids, acids,

alkalis.

• Hydrofluoric acid caus etching of the porcelain surface.

Esthetic Properties

• Excellent esthetic qualities

• Able to match adjacent tooth structure in

translucence, color and intensity

• Prvides life like appearance

Biocompatibility

• Excellent compatibility with oral tissuestissues