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1. A combination of
Metal-Ceramics

2. Dental Ceramics
Definition of Ceramics: inorganic, non-metallic
materials made by the heating of raw minerals at
high temperatures
Ceramics materials are fundamentally distinct from
alloys or polymers, they contain strong directional
ionic bonds between metals and oxygen that impart
strength but ll not tolerate distortion.
They are materials that are part of systems designed
with the purpose of producing dental prostheses that
in turn are used to replace missing or damaged
dental structures.

3. The classifications of dental ceramics
The following ceramics belong to the dental ceramic category: feldspar ceramics, leucite reinforced
ceramics, ceramics with low melting point, glass ceramics, high-strength core masses (alumina), glass
infiltrated alumina as well as CAD/CAM ceramics.
Dental ceramics are divided into different groups according to their chemical composition (feldspar,
leucite, alumina, glass alumina, and glass ceramics), application (tooth reconstruction, ceramic-covering
metals, veneers, inlays, crowns, and anterior bridges), the manufacturing procedure, or the structure of
the material (cast metal, burnished metal foil, glass ceramics, CAD/CAM ceramic, and sintered ceramic
core).
Sintering, pressing, casting, slip casting followed by glass infiltration, and machining (manually or
computer-operated) are the different manufacturing methods that can be used for making ceramic
restorations.

4. Why we use metal-ceramics for bridges and crown?
A metal-ceramic crown that has been correctly
produced is also more stable and more durable
than a regular jacket crown. However, a
metal-ceramic bridge involving several teeth can
fracture and chip the ceramic under stress due
to its inferior flexure strength. Because of this, it
is very important to consider occlusal conditions
when such a bridge is made.
Dental porcelain (also known as dental ceramic)
is a dental material used by dental technicians
to create biocompatible lifelike dental
restorations, such as crowns, bridges, and
veneers. Evidence suggests they are an
effective material as they are biocompatible,
aesthetic, insoluble and have a hardness of 7 on
the Mohs scale. For certain dental prostheses,
such as three-unit molars porcelain fused to
metal or in complete porcelain group

5. The origin of the word
Ceramic derived from Greek words
Keramikos- Earthen
Keramos- Burnt stuff

6. Advantages and Disadvantages of dental ceramics
● Advantages + :
● they can mimic tooth esthetics
better than other materials
● they ate brittle
● high compressive strengths
● impervious to oral fluids
● biocompatible
● long-lasting aesthetic quality.
● Disadvantages - :
● tendency to wear natural teeth
and damage edentulous ridges
● low tensile strength and
elongation

7. Ceramic- Alloy Restoration
Ceramic - alloy restorations remain the most common type of ceramic dental
restoration.
The consist several layers of ceramic bonded to an alloy substance. The alloys
sub. is less than 0.5mm thick in the area that ll be covered.
They are used mostly used for prosthetic teeth restoration and long-span bridges.
If they are done in proper way, they provide truly excellent esthetics that may be
nearly imperceptible from the natural tooths. Error in manipulation not only
compromise with the esthetics of the restoration but its physical integrity as well.

8. Statistic which show the value of dental ceramics
Metal-ceramic crowns and bridges show success rates of 97% during the first
seven and a half years.
After 10 years, 95% of the metal-ceramic restorations are still present in the oral
cavity.
However, the success rate after seven and a half years refers only to noble metal
alloys with a gold content of at least 40% as well as castings with conventional
metal margins.

9. Cross-section diagram of ceramic- alloy restoration
Dental Materials Properties and Manipulation J.M.Powers J.C. Wataha

10. Ceramic Alloy Bonding
Most of the restoration can fail after a short time that is why we use ceramic alloy
bond.
Its is a fundamental to success of ceramic alloys restoration because the stress
induced in the ceramics by oral force can be shared and supported by the alloys.
Durability of the ceramic alloy bond is paramount to clinical process.

11. The bonding way
Ceramic bond to alloy by oxide on the alloy surface. Alloys for the ceramic alloys
restoration are nearly always specially formulated so that an oxide will form. When
ceramic is fired onto the alloy surface a chemical reaction between the oxide layer
of the alloy and the ceramic occurs, which creates the ceramic- alloy bond.

12. Strong directional ionic bonds between metals and oxygen

13. Complications with bonding
An debonding of the ceramic from the alloy after the restoration has been
permanently cemented can cause esthetic or functional failure of the restoration.
Repair often require complete replacement, including removal of the old-metal
substructure and fabricate of a new metal substructure and ceramic material. The
effects of ceramic alloy debonding are expensive and traumatic for the patient and
should be prevented if at all possible.

14. Failures of ceramic alloy
The failure of alloy ceramic bonds can occur of different causes. Example: the alloy might have insufficent
oxide layer, the result of this problem will lead weak ceramic alloy-bond.
Another cause is the formation layer of the oxide can be to thick, this will increase the risk of fracture in
the ceramic-alloy bond which means failure as well.
Most common failure in the ceramic-alloy bond is the failure of the ceramic layer itselt which is near the
alloy-ceramic interface.
Only a limited amount of information is available on crowns with ceramic shoulders. It may be possible
that ceramic margins crack under high pressure and finally fracture. Data on metal-ceramic crowns that
are built on titanium frameworks are not yet available. Therefore, the use of the latter crowns is
recommended exclusively for the treatment of anterior teeth.