1. DENTAL CERAMICS
Kuo-lung Tung
0901

2. DENTAL CERAMICS

3. 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

4. DENTAL PORCELAIN
Dental Porcelain = an early type of dental ceramics that has been modified to improve its properties
APPLICATIONS OF PORCELAIN
1. Porcelain denture teeth
2. Porcelain jacket crown
3. Porcelain inlay
4. Porcelain veneer
5. Porcelain fused to metal prosthesis
6. Implant material

5. COMPOSITION OF DENTAL PORCELAIN
A. Feldspathic porcelain
Fired material is composed of
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

6. COMPOSITION DENTAL PORCELAIN
B. Aluminous porcelain
The 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.

7. Classification of Dental Porcelain
A. According to their fusion temperatures
1- High-fusing ( oC)
2- Medium-Fusing ( oC)
3- Low-Fusing ( oC)
4- Ultra-Low- Fusing (< 850oC)
1 & 2 are used for denture teeth production
3 & 4 are used for crown and bridge construction
B. According to the method of their firing
1- Atmospheric firing
2- Vacuum firing (lower % of porosity)

8. Classification of Dental Porcelains
C. According to their clinical applications
1. Core porcelain:
Used to form the basal layer of jacket crown
2. 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
Manipulation Of Dental Porcelain
(Powder-slurry technique)  Watch the video

9. CHARACTERS OF DENTAL PORCELAIN
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

10. CHARACTERS OF DENTAL PORCELAIN (Cont.D)
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

11. Metal-ceramic restorations

12. Metal-Ceramic Restorations
Incisal (enamel) porcelain
Body (dentine) porcelain
Metal substructure
Opaque porcelain
These restorations are composed of; Metal substructure (Coping) supporting a ceramic veneer those are chemically and mechanically-bonded together

13. Benefits and drawbacks of the metal-ceramic restorations
Advantages:
1. Stronger than porcelain crowns
2. Can be used for constructing long-span bridges
3. Good esthetic and less liable to staining
4. High wear resistance
5. Long term clinical durability ( 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 area
3. Using opaque porcelain is essential to overcome the metal color
4. Special properties of the metal coping are required for proper results (see the next section….)

14. Requirements of the metal coping
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.

15. Bonding of porcelain to the metal copings
Irregularities
Oxide layer
Metal
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.

16. 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.

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

18. Production of Metal copings
A. Casting of pure metals or metallic alloys
1- Commercially-pure titanium (CP Ti)
2- High gold alloy Gold-palladium alloy
4- Palladium-silver alloy High palladium alloys
6- Nickel- chromium alloy
B. Burnishing and heat treating metal foils on a die
1- 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

19. All-CERAMIC RESTORATIONS

20. Advantages of all-ceramic restorations
Biocompatibility
Superior esthetic (No metal display)
Good bonding (cohesion) between the ceramic coping and the porcelain veneer
Acceptable mechanical properties
Superior hardness that provides the restoration its wear resistance
Resist the degradation in oral fluids
Low thermal diffusivity
Most systems could be used for constructing inlays, onlays and crowns

21. 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

22. Families of all-ceramic restorations
Powder-slurry ceramics
Castable ceramics
Machinable ceramics
Pressable ceramics
Infiltrated galss ceramics

23. Powder-slurry ceramics
The material presents as powder to be mixed with liquid forming a slurry that is used to build the restoration up
e.g. (1) Optec HSP, (2) Duceram system

24. 2. Castable ceramics
Ceramic ingot is fused and cast in a refractory (investment) mold made by the lost wax technique
e.g. (1) Dicor, (2) Dicor Plus, (3) Castable Apatite

25. 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

26. CAD-CAM Technology

27. 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

28. Copy-milling Technology

29. 4. Pressable ceramics
Ceramic ingots are softened by heat and pressed into a refractory mold using special alumina injector
e.g. (1) Optec Pressable Glass Ceramic, (2) IPS Empress ,(3) Empress 2, (4) IPS e.max press

30. 5. Infiltrated glass ceramics
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
e.g.(1) In-Ceram Alumina, (2) In-Ceram Spinel, (3) In-Ceram Zerconia