in this lecture we will discuss porcelain fused to metal parts, the definitions, types, properties, uses and how to make a successful MCR.

1. Factors affects
of the
successful of
MCR
Organized by :
- DT Sarah Omari
Done by :
- Mohammad Alsalhi
- Qais Meqdad
- Qutaiba Aljarar‘ah

2. Topics
 For MCR
• Definition of MCR.
• Parts of MCR.
• Advantages &Disadvantages of MCR.
 For Ceramic
• Definition of ceramic, Composition
• Basic structure.
• Ceramic properties.
• Advantages & Disadvantages of ceramic.
• Parts of ceramic.
• Uses of dental ceramic.
• Firing procedure.
 For Metal
• Types of Metal.
• Metals properties.
 Factors effects of the successful of MCR
• Factors related to patient.
• Factors related to clinicians.
• Factors related to the selected dental material.
• Factors related to laboratory fabrication.

3. For MCR

4. Definition
• Definition of Metal-Ceramic Restoration (MCR):-
• A fixed restoration that employs a metal substructure on which a
ceramic veneer is fused.
- known as Porcelain fused to metal (PFM).

5. Parts of MCR
• Core:- cast metallic framework. Also known as coping.
• Opaque Porcelain:- first layer consisting of porcelain modified
with opacifying oxides.
• Dentin and enamel porcelain build up.

6. Advantages & Disadvantages of MCR
 Advantages:-
• Stronger than all-ceramic crowns.
• Can be used for constructing long-span bridges.
• Acceptable aesthetic.
• High wear resistance.
• Excellent fit of the metal framework.
 Disadvantages:-
• Potential metal allergy.
• Inferior esthetics compared to all ceramic crown.
• Unaesthetic metal margins.

7. For Metal

8. Types of Metals
 Noble metals:-
a) Gold, palladium, platinum.
b) High resistivity to corrosion.
 Non-noble metals:-
a) Titanium, nickel, copper, silver, zinc.
b) Provide modulus of elasticity and abrasion resistance of dental alloys.

9. Metals properties:-
 Usually are:
• Strong and hard.
• Able to polished.
• High density is dependent on molar mass of molecule as well as
structure type of crystalline.
• Good heat and electricity conductors.
• Melting temperature.

10. Metal properties
alloys strength
• Yield point – indicates force applied to the surface unit at which
permanent deformation will appear.
• Yield point unit is Mega pascal (MPa) yield point for alloys is in the
range of :- 260-1150 Mpa.
• Alloy deformation – magnitude express in percentage (%).
• Yield point 750 MPa and deformation 0,2% - it means that force of
750 MPa is causing deformation of alloy by 0,2%.

11. Metal properties
hardness
• Influences polish of alloy.
• Hardness is related to yield point.
• Hardness is express in kg/mm.
• Hardness of dental alloys is in the range:125 – 425 kg/mm.
2
2

12. Metal properties
alloy density

13. Metal properties
melting temperature range
• Metal alloys are melting in specific temperature range.
• During the heating melting temperature range: 950-1000 C.
• 950 C first symptoms of melting.
• 975 C part of the alloy is liquid but some of the components are still
solid.
• 1000 C entire alloys become liquid.

14. Metal properties
melting temperature range
• Liquidus - temperature in which alloy entirely become liquid.
• Solidus – temperature in which alloy during the cooling became solid.
• Alloy may be used for casting when its temperature is higher than
liquidus.
• Solidus is important during soldering.
• If soldering will make alloy warmer above solidus than shape change
may occur.

15. For Ceramics

16. Definition
• Ceramic is defined as a product made from nonmetallic material by
firing at a high temperature.
• It mainly consist of silicate glasses, porcelains, glass ceramics, or
highly crystalline solids.
• Wide variety of porcelain products available in the market.
• So its virtually impossible to provide a single composition for them all.
• So we will discuss about traditional porcelains.
- feldspathic porcelains.

17. • Basically porcelain is a type of glass.
- Three dimensional network of silica (silica tetrahedral).
• Since Pure glass melts at too high a temperature.
– Modifiers added to lower the fusion temperature
– Sodium or potassium.
• But this weakens the strength and make it brittle.
Basic Structure

18. Properties of dental ceramic
 Highly esthetic.
 Translucent material.
 Strong.
 Wear resistant.
 Biocompatible.

19. Advantages & Disadvantages
 Advantages:-
1. Biocompatible as it is chemically inert.
2. Excellent esthetic.
3. Thermal properties are similar to those of enamel and dentine.
 Disadvantages:-
1. High hardness causes abrasion to antagonist natural dentitions and difficult to
adjust and polish.
2. Low tensile strength so it is brittle material.

20. Parts of ceramic
A. Opaque porcelain:-
- Mask the darkness of the oxidized metal framework.
- metal-ceramic bond.
B. Body or dentin porcelain:-
- Makes up the bulk of the restoration by providing most of the color or
shade.
C. Enamel porcelain:-
- It provides the translucent layer of porcelain in the incisal portion of the tooth.
- Enamel hardness is 343 kg/mm.
2

21. Glazing
 The glazing is to obtain a smooth surface that simulates a
natural tooth surface.
 It is done either by:-
I. Auto glazing:- rapid heating up to the fusion temperature for 1-2
minutes to melt the surface particles.
II. Add on glazing:- applying a glaze to the surface and re-firing.
Auto glazing is preferred to an applied glaze.

22. Uses of dental ceramics
• Inlays and onlays.
• Esthetic laminates (veneers) over natural teeth.
• Single (all ceramic) crowns.
• Short span (all ceramic) bridges.
• As veneer for cast metal crowns and bridges (metal ceramics).
• Artificial denture teeth (for complete denture and partial denture use).
• Ceramic orthodontic brackets.

23. Dental ceramic classifications
1- Based on the Application 2- Based on the Fabrication
Method
3- Based on the Crystalline
Phase
 Metal-ceramic: crowns, fixed
partial prostheses
 All-ceramic: crowns, inlays,
onlays, veneers, and fixed
partial prostheses.
 Additionally, ceramic
orthodontic brackets, dental
implant abutments, and ceramic
denture teeth.
 Sintered porcelain: Leucite,
Alumina, Fluorapatite.
 Cast porcelain: Alumina,
Spinel.
 Machined porcelain: Zirconia,
Alumina, Spinel.
 Glassy (or vitreous) phase.
 Crystalline phases.

24. Firing or sintering
 It is to fuse the particles of porcelain powder producing hard mass.
 Stages of firing:-
A. Low bisque stage:- Particles lack complete adhesion, low amount of
shrinkage occur, and very porous.
B. Medium bisque stage:- water evaporates with better cohesion to the powder
particles and some porosity .
C. High bisque stage:- fusion of particles to form a continuous mass, complete
cohesion and no more shrinkage.

26. Factors
effects of the
successful of
MCR

27. Factors
related to
patient
Factors
related to
clinicians
Factors
related to the
selected
dental
material Factors
related to
laboratory
fabrication

28. Factors
related to
patient

29. Acquired(Habits) Congenital
 Trauma
 Physical trauma is one
of the major causes of
porcelain fracture such
as fall, fight, road-traffic
or sports accident.
 Injudicious use
 Uses the prosthesis
roughly such as to bite
hard food like nuts.
 Increased overbite
 A great amount of
vertical overlap causes
excessive non-axial
forces may lead to
fracture of the
restoration. However,
this factor affects
anterior restorations
only.
 Occlusal
interferences
 Premature contacts in
centric and eccentric
movements generate
increased localized
stresses in the porcelain.
which may lead to
chipping the porcelain.

30. Factors
related to
clinicians

31. 1- Insufficient tooth
reduction
2- Inadequate finish line 3- Inadequate impression
recording & wax bite
 Uneven tooth preparation may
result be an over-contoured,
bulky, opaque-looking crown, or
if the porcelain is too thin, it will
be more liable to failure.
 Thin finish line (knife edge
finish line) designs have been
shown to be more susceptible to
chipping and fracture, especially
during the try-in and
cementation.
 This factor affects all
restorations, and not just metal–
ceramic ones. An impression of
the prepared tooth that has been
poorly recorded.
 Occlusal registration ( wax bite )
may also affect the accuracy of
the restoration and cause a
premature occlusion.

32. Factors
related to the
selected dental
material

33. 1- Thermal
incompatibility of
materials
2- Elastic modulus of the
metal
3- Use of weak material
with low fracture
toughness
4- Implant-supported
prostheses
 A large difference in the
coefficient of thermal
expansion of metal and
ceramic, where ceramic
contracts more than the
metal, can generate
excessive tensile stresses
in the ceramic layer, thus
promoting fracture. Such
a thermal mismatch
between the core
porcelain and the veneer
porcelain may lead to
increased failure of metal-
ceramic systems.
 The higher the elastic
modulus, the stiffer will
be the material and better
able to resist deformation
under loading. An alloy
with low modulus of
elasticity will flex under
loading, yield poor
support to porcelain and
increase the risk of
porcelain fracture.
 Choosing a right material
in the right place.
 Metal-ceramic
restorations on implant-
supported prostheses are
more prone to fracture as
compared to the ones on
tooth-supported
prostheses. This is
probably because
implants lack the resilient
periodontal ligaments that
help in the detection of
excessive occlusal loads.

34. Factors
related to
laboratory
fabrication

35. 1- Coping design 2-Design of connectors 3-Poor metal-ceramic bond
 A metal–ceramic restoration is
likely to fail if the coping does
not meet six important design
features including:-
1. Thickness of the porcelain
veneer.
2. Thickness of metal underlying
the porcelain.
3. Placement of occlusal and
proximal contacts.
4. Extent of the area to be
veneered.
5. Proper of the facial margin.
 For clinical longevity,
connectors of a fixed partial
denture should be enough
thickness and height to resist the
occlusal loads. However, for
optimal aesthetics, occlusal and
gingival embrasures must be
created.
 A metal-ceramic bond results
from the interplay of a number
of different factors including
mechanical and chemical
bonding.

36. Thank you
for
your time