Kuo-lung Tung0901

DENTAL CERAMICS

DENTAL CERAMICS

DENTAL CERAMICS

Generally the word ceramic is used to name any material having both metallic and non-metallic ions in its compositional formula

e.g. cements, gypsum, porcelain and glasses

Dental Porcelain = an early type of dental ceramics that has been modified to improve its properties

APPLICATIONS OF PORCELAIN

1. Porcelain denture teeth2. Porcelain jacket crown3. Porcelain inlay4. Porcelain veneer5. Porcelain fused to metal prosthesis 6. Implant material

DENTAL PORCELAIN

A. Feldspathic porcelain

Fired material is composed of

1. Glassy phase (Vitreous matrix made of feldspars) Feldspars are mixture of Anhydrated alumino-silicates

of both…. Potash feldspar = K2O. Al2O3. 6 SiO2 And

.… Soda feldspar = Na2O. Al2O3. 6 SiO2

2. Dispersion of crystalline phase (mineral phase including silica and other oxides)

Main characters• Void of kaolin • Technically it is a glass rather than true porcelain• They are translucent

COMPOSITION OF DENTAL PORCELAIN

B. Aluminous porcelainThe porcelain material contains 40-50% alumina crystals (Al2O3) in a low-fusing glass matrix.

High-Ceram The dispersed alumina particles are much stronger

with higher modulus of elasticity and coefficient of thermal expansion than those of the glassy matrix.

Presence of alumina makes the material opaque. (used only as coping beneath regular porcelain)

In-ceram alumina It is not only a kind of infiltrated glass ceramic, but

also considered as one of the aluminous porcelains.

COMPOSITION DENTAL PORCELAIN

A. According to their fusion temperatures1- High-fusing (1300-1400oC)2- Medium-Fusing (1100-1300oC)3- Low-Fusing (850-1100oC)4- Ultra-Low- Fusing (< 850oC)

1 & 2 are used for denture teeth production3 & 4 are used for crown and bridge

construction

B. According to the method of their firing1- Atmospheric firing2- Vacuum firing (lower % of porosity)

CLASSIFICATION OF DENTAL PORCELAIN

C. According to their clinical applications1. Core porcelain:

Used to form the basal layer of jacket crown2. Dentine or Body porcelain:

More translucent, used to build the body of crowns

3. Enamel porcelain:The most translucent, used to form the incisal

edges

CLASSIFICATION OF DENTAL PORCELAINS

Manipulation Of Dental Porcelain

(Powder-slurry technique) Watch the video

1. Biological Properties:• Inert has no interaction with surrounding soft

tissue (biocompatible)

2. Interfacial Properties:• Not adhere chemically to dental cements

3. Chemical properties:

• Not soluble in oral fluids and resist acid attach• Both hydrofluoric acid and stannous fluoride can

cause an increase in surface roughness

4. Mechanical Properties:• Brittle • Low DTS and fracture toughness• Hard, can cause wearing of opposing dentition

CHARACTERS OF DENTAL PORCELAIN

5. Thermal Properties:•Low thermal diffusivity

•Coefficient Of thermal expansion similar to that of enamel and dentine

6. Esthetic properties:•Excellent esthetic, and color matching

•Difficult to be stained

7. Practicability:•Sensitive manipulation technique, Requiring skilled operator and Special equipments

•Firing shrinkage is always, So operator should build up the restoration to a bigger size that allows shrinkage

CHARACTERS OF DENTAL PORCELAIN (CONT.D)

Metal-ceramic restorations

These restorations are composed of; Metal substructure (Coping) supporting a ceramic veneer those are chemically and mechanically-bonded together

Metal-Ceramic Restorations

Metal substructureOpaque porcelain

Body (dentine) porcelain

Incisal (enamel) porcelain

Benefits and drawbacks of the metal-ceramic restorations

Advantages:1. Stronger than porcelain crowns 2. Can be used for constructing long-span bridges3. Good esthetic and less liable to staining4. High wear resistance5. Long term clinical durability (2.3-7.5 years)6. Less preparation is required in comparison to all-ceramic

restorations

Disadvantages:1. Sufficient metal bulk (0.3 mm) is required for proper rigidity 2. Metal display could result at the thin marginal area3. Using opaque porcelain is essential to overcome the metal

color4. Special properties of the metal coping are required for

proper results (see the next section….)

1. Has melting temperature higher than the porcelain firing temp. (to avoid sagging at the time of porcelain firing)

2. Able to form an oxide layer that provides the chemical bond to porcelain (presence of indium or tin in high noble alloys is essential for that purpose. e.g gold alloys)

3. Has coefficient of thermal expansion a little bite higher than that of porcelain (to provide higher mechanical bond)

4. Has no greening effect on the porcelain color

5. High high elastic modulus (E) to resist the bending and the cracking of porcelain under masticatory force.

REQUIREMENTS OF THE METAL COPING

BONDING OF PORCELAIN TO THE METAL COPINGS

1. Mechanical bonding: - Infiltration (flow) of the fused ceramic into the surface irregularities of the metal coping. - Sandblasting of the metal surface or using plastic beads during waxing are important for this issue.

Metal

Porcelain

Oxide layerIrregularities

Bonding of porcelain to the metal copings

2. Chemical bonding: - Ionic bond between the metal oxide layer and the opaque

porcelain. - Metal degassing is important for oxide formation, removing

the surface contaminants and greases. - Thin oxide layer (in case of noble alloys) provides stronger

bond than the thick one (in case of base metal alloys).

3. Coeff. of thermal expansion mismatch: As a result of higher metal contraction on cooling , - The fused porcelain will be sucked (attracted) more strongly

into the metal surface irregularities.- Residual compressive stresses will developed in and

strengthen the porcelain.

4. Application of a special bonding agent:Certain metal system (electro-forming) requires the application of specific bonding paste before building-up the porcelain.

Bonding of porcelain to the metal Copings

Production of Metal copings

A. Casting of pure metals or metallic alloys1- Commercially-pure titanium (CP Ti) 2- High gold alloy 3- Gold-palladium alloy 4- Palladium-silver alloy 5- High palladium alloys 6- Nickel- chromium alloy

B. Burnishing and heat treating metal foils on a die1- Platinum foil 2- Gold foil 3- Captek system

C. Electro-deposition of metal on a duplicate die

D. CAD-CAM processing of a metal ingot

ALL-CERAMIC RESTORATIONS

ADVANTAGES OF ALL-CERAMIC

RESTORATIONS

BiocompatibilitySuperior esthetic (No metal display)Good bonding (cohesion) between the ceramic

coping and the porcelain veneerAcceptable mechanical propertiesSuperior hardness that provides the restoration its

wear resistanceResist the degradation in oral fluidsLow thermal diffusivityMost systems could be used for constructing inlays,

onlays and crowns

Disadvantages of all-ceramic restorations

High cost of the materials and the processing equipments

Excessive tooth reduction is needed

Most systems utilize feld-spathic porcelain coating to provide the desired color and contour

Most systems are not suitable to construct long span bridge

1. Powder-slurry ceramics2. Castable ceramics3. Machinable ceramics4. Pressable ceramics5. Infiltrated galss ceramics

Families of all-ceramic restorations

The material presents as powder to be mixed with liquid forming a slurry that is

used to build the restoration up

1. POWDER-SLURRY CERAMICS

e.g. (1) Optec HSP, (2) Duceram system

Ceramic ingot is fused and cast in a refractory (investment) mold

made by the lost wax technique

2. CASTABLE CERAMICS

e.g. (1) Dicor, (2) Dicor Plus, (3) Castable Apatite

3. Machinable ceramics

CAD- CAM technology

The prepared tooth is optically impressed (pictured using intra-oral camera). The restoration is design over that image by the aid of computer……Then

Ceramic blocks are carved into restorations by the aid of computer-controlled milling machine

e.g. (1) Cerec Vitablocks-mark I, (2) Cerec Vitablocks-mark II, (3) Dicor MGC Blocks

CAD-CAM Technology

3. Machinable ceramics

Copy-Milling technology

The prepared tooth is impressed poured in gypsum to form a die.

A wax pattern is built over the die……Then Ceramic blocks are carved into restorations by the aid of computer-controlled milling machine that is

guided by the constructed wax patter

e.g. (1) Celay blocks (2) Lava Zerconia, (3) Cercon

Copy-milling Technology

Ceramic ingots are softened by heat and pressed into a refractory mold

using special alumina injector

4. PRESSABLE CERAMICS

e.g. (1) Optec Pressable Glass Ceramic, (2) IPS Empress ,(3) Empress 2, (4) IPS e.max press

A porous crystalline slip is formed by fusion of Metallic particles at high temperature.

A Glass coat is then fused over the porous slip to infiltrate into the pores and strengthen the structure.

Veneering porcelain is then required to provide the desired shade and contour

5. INFILTRATED GLASS CERAMICS

e.g.(1) In-Ceram Alumina, (2) In-Ceram Spinel, (3) In-Ceram Zerconia