this presentation descripting the meaning of ceramo-metalic restorations, different shapes of this material , methods of fabrication and the failure mode

1. CERAMO-METALLIC
RESTORATIONS
BY
Dr/Ahmed Gamal

2. Definition
Components
Requirements of alloys, porcelain, tooth preparation & metal framework design.
Ceramo-metallic bonding mechanism
Failure of Ceramo-metallic bond
Techniques Of Construction Of Metal Substructure

3. Definition

4. Metal-Ceramic Restoration ,
Ceramo-Metallic Restoration ( CMR),
Porcelain Fused to Metal (PFM)

5. • It is a full coverage fixed restoration .
• It is composed of metal coping ( metal substructure ), which fit over
the tooth preparation and ceramic veneer that is mechanically and
chemically fused to the coping.

6. WHAT are the CMR
restorations in fixed
prosthodontics .
????

7. Veneered crown

8. Full Veneered Crown

9. CMR are the most popular
restorations used in fixed
prosthodontics .
WHY????
 Because they combine both high strength of metal substructure and
good esthetics of ceramic veneer.

10. Components

11. Metal-
Ceramic
Restorations
Metal
Substructure
Porcelain
Veneer
Opaque
Dentin
(Body)
Enamel
(Incisal)

12. WHAT is the role of each
components of CMR .
????

13. • It is fitting over the prepared tooth.
• It plays an important role in the support the
porcelain veneer due to lack of strength of
conventional low fusion porcelain .

14. • Allow rigidity to avoid bending or flexing of metal under occlusal force.
• Metal thickness:
• Precious Alloys: (0.3-0.5 mm )
• Base Metal Alloys:( 0.2-0.3mm)

15. Metal thickness :
Precious Alloys: (0.3-0.5 mm )
Base Metal Alloys:( 0.2-0.3mm)
WHY Difference between
both??
Alloys can be finished in thin sections &
withstand distortion

18. • It masks the underlying metal.
• It plays an important role in the
development of the bond between
the ceramic and the metal.
• The opaque thickness: (0.2 mm)

19. Opaque Porcelain
masks the underlying
metal. HOW????
 By adding of Oxides ( high
refractive index)
to the original porcelain which
leads to refract the light rather
than transmission.

21. 3.Dentine,
or Body
Porcelain
Fired onto the opaque layer , together
with enamel porcelain
Make up the bulk of the restoration
 Providing most of the color, or shade.

23. • It imparts translucency to the restoration
• It fired together with the dentin porcelain.

25. • The final color of CMR
depends on which:
• Dentine Porcelain
or
• Enamel Porcelain
???? Dentine Porcelain.

28. 5.Glazing
It gives the luster & glossy appearance
of CMR
It may be :
Add on glaze or ,
Auto glaze( Self-glazing )

29. 1-Add on glaze:
Low fusing ceramic powders painted on die surface of the
restoration fired at temperatures less than the maturing
temperatures of the restoration

30. 2-Auto glaze( Self-glazing ):
Following final contouring additional firing in air is done
without adding any glaze material and maintained for a time
before cooling.

31. Which is less destructive
to the opposing tooth
structure Polished or
Glazed Porcelain ????
Polished Porcelain.

32. Requirements Of Alloys Used For CMR

33. • They must have a higher melting range than the firing temperature or
porcelain.
• The minimum difference is 300-500 ºF ( 165-275 ºC)
• The greater the difference, the fewer the problems that encountered
during firing.

34. What happens if the
difference between the
two materials is less
than170?????????
Distortion or melting of the coping during firing and
glazing of the porcelain.

35. • They must match the porcelain in regard to the coefficient of
thermal expansion (slight difference )
• The optimum difference between the two would be NO greater
than 1× 10-6ºC.
• It must have a higher coefficient of thermal expansion for the
coping than for the porcelain veneered over

36. Why the coefficient of
thermal expansion must
higher for the coping than
for the porcelain veneered
over ?????????
To avoid production of shear stress that lead to failure of
the bond between porcelain & metal.

37.  The alloy should be rigid enough WHY????
-Not flex during seating or when subjected to occlusal forces.
-Any flexing will lead to shearing of the porcelain

38. The alloy should
NOT contain
copper or
silver…….WHY????
To avoid discoloration of the enamel
porcelain

39. The alloy should be high temperature
strength (sag resistance)
The alloy should be High hardness
Capable of forming a strong bond
with porcelain.

40. Requirements Of Porcelain

41. • They must have less than the melting range of the metal alloy .
• The minimum difference is 300-500 ºF ( 165-275 ºC)
• They should be of a low fusion type.
• ( 860-1260 ºC)

42.  They must match the porcelain in regard to the coefficient of
thermal expansion (slight difference )
 The optimum difference between the two would be NO
greater than 1× 10-6ºC.
 It must have a lower coefficient of thermal expansion for the
porcelain than for the metal alloy

43. • Resistance to pyroplastic flow,( slumping )
• i.e. it is required to maintain its shape during firing
• Alumina in feldspar ceramic is responsible for resistance of
pyroplastic flow

44. Chemical & optical stable over a series of
firing cycles

45. • When porcelain is fired too many times, it
may devitrify, thus become milky and
difficult to glaze.

47. Requirements Of Tooth Preparation

48.  Facial & proximal reduction
Thickness (1.2-1.5 mm)
End in a shoulder finish line
→ bulk for metal and porcelain
 Lingual reduction (0.5mm) → metal.

49. Different finish line designs on facial surface:
90°shoulder,beveled shoulder and shoulder with bevel

50. Shoulder with bevel is better in
marginal adaptation.. WHY???

51. Requirements Of Metal Framework Design

52. For adequate strength and rigidity.
Due to brittleness of porcelain must
support from underlying metal.
Avoid porcelain fracture

53. Thick porcelain lead to fracture due to:
occur under tension & sub-surface porosity.

54. • - A noble metal coping should at least (
0.3 - 0.5 mm )thick.
• - A base metal alloy with higher yield
strength, high melting range and high
modulus of elasticity may be as thin as
0.2mm.
Thickness of Metal:

55. A dial caliper to
confirm the
metal thickness

56. What happens if the
thickness too thin or
too thick ?????????
TOO THIN ----- Distortion or cracking
of the porcelain during seating.
TOO THICK------Color variations

59. • Deficiencies in incisal edge or cusps should be compensated with extra METAL
thickness NOT of porcelain. WHY??????
• Thickness of Porcelain :
• minimum =0.7 mm
• optimum =1 mm
• maximum = 1.5 mm

60. Thick porcelain lead to fracture
due to:
• occur under tension & sub-
surface porosity

62. - Eliminate stress concentration areas
- Even occlusal forces distribution
- Facilitate wetting of metal substructure
by porcelain slurry , so enhancing of
bonding
WHY????

65. - Away from P/M Junction to avoid
porcelain fracture
- Biocompatibility due to less wear
- Easy in construction
It should be in METAL when ever possible
…WHY????

66. • Occlusal extensions of veneered
material
• (Away from P/M
Junction)

70. Occlusal Contacts
should away from
P/M Junction to
avoid porcelain
fracture

71. In anterior teeth ,it should be on
Porcelain for better esthetic &
translucency.

73. In posterior teeth:
On the mesial the
preparation
extends farther
than the distal

74. • For better esthetics & translucency
• Avoid porcelain fracture & splitting under
masticatory forces

77. Facial extensions of
veneered material
Metal collar Collarless

78. Which is better metal
collar OR
collarless?????????
- Depends on :
Adaptation & esthetic needed

80. •Finishing of the metal
coping in CMR should
be carried out in one
direction &using
light pressure
WHY????

81. • to avoid :
• dragging of the metal ,
• entrap air between folds of the metal &
• accumulation of debris in the irregularities of the
porcelain

83.  In CMR( high gold content alloys) require oxidizing cycle before
opaque application. WHY????
to establish chemical bond with the veneering ceramic.

84. Ceramo-metallic Bonding
Mechanism

85. Metal-Ceramic Bonding
Mechanical Chemical Compression

87. Mechanical
bonding :
• By mico-roughness ( air- abrasion)
To :
• mechanical interlocking ,
• enhance wettability , surface
area for chemical bonding.

88. Chemical
bonding :
• Formation of oxide layer .
• Gold alloys, from tin, indium or gallium
• Base metal alloys , from chromium oxide

89. Compressive
bonding :
• Due to the slightly smaller
coefficient of thermal expansion of
porcelain than for the metal alloy
(1× 10-6ºC)

90. Ceramo-metallic Bonding
Failures

92. Techniques Of Construction
Of Metal Substructure

93. -Electroforming technology .
-Metal foil technology .
(Captek system)
• 1- Lost wax casting technique ( cut back )
• 2- Alternative techniques

94. Lost Wax Casting Technique
( Cut Back )

98. Captek
System

99. Deposition of thin
pure gold coping
before porcelain
application
Electroforming Technology

101. Thank you