Composition, Microstructure,Properties ,Applications & Advanced

techniques of Dental ceramics

ByMohamed Mahmoud Abdul-Monem

Dental ceramics

An inorganic compound with non-metallic properties typically consisting of oxygen and one or more metallic or semi-metallic elements(e.g Al,Ca,Li,Mg,K,Si,Na,Sn,Ti,Zr)

Dental ceramics• Predominantly glass• Particle filled glasses• Polycrystalline ceramics

Predominantly glass ceramics

Composition • Glass-based systems are made from materials

that contain mainly silicon dioxide (also known as silica or quartz), which contain various amounts of alumina.

• Aluminosilicates found in nature, which contain various amounts of potassium and sodium, are known as feldspars. Feldspars are modified in various ways to create the glass used in dentistry.

Predominantly glass ceramics

Microstructure

Microstructure of glass ceramics

Predominantly glass ceramics

Properties• Mimic the optical properties of Enamel and

Dentin.• Resistant to crystallization (devitrification) .• Brittle.• Biocompatible.

Predominantly glass ceramics

Applications• Veneers• Inlays• Onlays• Veneers for ceramic substructures(alumina

and zirconia cores)

Particle filled glasses

• Moderately filled glasses• Highly filled glasses

Particle filled glassesComposition

• Filler particles are added to the base glass composition to improve mechanical properties and to control optical effects such as opalescence, color, and opacity.

• These fillers are usually crystalline but can also be particles of a higher melting glass.

Particle filled glasses

Moderately filled glasses • Leucite (17-25%)• Leucite is potassium aluminium silicate

kAlSi2O6

Particle filled glassesLeucite filled glassMicrostructure

Moderately filled glassProperties

• Increased mechanical properties• Leucite increase the COTE (used for PFMs)• leucite was chosen because its index of refraction

is close to that of feldspathic glasses, an important match for maintaining some translucency.

• leucite etches at a much faster rate than the base glass, and it is this ‘‘selective etching’’ that creates a myriad of tiny features for resin cements to enter, creating a good micromechanical bond.

Moderately filled glass

Applications• Veneers for metal substructures(PFM)• Inlays • Onlays• Veneers

Highly filled glass ceramics

• Strength increases can also be achieved with appropriate fillers added and uniformly dispersed throughout the glass, a technique termed ‘‘dispersion strengthening.’’

• The first successful strengthened substructure ceramic was made of feldspathic glass filled with particles of aluminum oxide (55 mass%) .

• Leucite also is used for dispersion strengthening at concentrations of (40 to 55 mass%), which is much higher than needed for metal-ceramics.

Highly filled glass ceramicsComposition Uses

Feldspathic glass +Leucite (40-55%)

Pressable ceramics

Single unit crownsInlays

Onlays Veneers

Feldspathic glass +Aluminium oxide (55%)

Single unit crowns

Lanthanum glass+Aluminium oxide (70% vol )

In-Ceram alumina

Single unit crowns3-Unit anterior bridges

Aluminoborosilicate glass+Zirconium oxide (20% vol)+aluminium oxide (50%

vol)

In-Ceram Zirconia

Single unit crowns3-unit bridges

Lithium disilicate (70%) Pressable ceramics

Single unit crowns3-Unit anterior bridges

Pressable ceramics containing Leucite

In Ceram Alumina

Lithium disilicate glass(IPS Empress II)

Polycrystalline Ceramics

Composition• Have no glassy component• All of the atoms are densely packed into

regular arrays that are much more difficult to drive a crack through than atoms in the less dense and irregular network found in glasses.

Polycrystalline ceramicsMicrostructure

Aluminium oxide

Microstructure

Zirconium oxide

Polycrystalline ceramics

Properties• Tougher and stronger than glass ceramics• More difficult to process into complex shapes • Opaque

Polycrystalline ceramics

Applications

Aluminum oxide Single unit crowns

Zirconium oxide Single unit crowns3-unit bridges4-Unit bridges

Techniques of dental porcelain fabrication

• Conventional condensation and sintering• Pressure molding and sintering • Casting and ceramming• Slip-casting and glass infiltration

Conventional condesation and sintering PFM

Conventional condensation and sintering ALL CERAMIC (platinum foil matrix 0.001 inch)

Pressure molding and sintering

Pressure molding and sintering

Casting and ceramming

Slip-casting and glass infiltration

Slip cast ceramics

• Alumina based (In ceram Alumina)• Spinell based (In ceram spinell) Magnesium

spinell MgAl204 • Zirconia-based (In ceram zirconia)

Advanced techniques for porcelain fabrication

• Machining and Milling (CAD-CAM)

Copy milling(Celay system)

References • R Giordano and E A. McLaren. Ceramics

Overview: Classification by Microstructure and Processing Methods. Compendium of Continuing Education in Dentistry.2013

• J R Kelly, P Benetti . Ceramic materials in dentistry: Historical evolution and current practice . Australian Dental Journal .2011;56:84-96

Thank you