Different fabrication techniques of ceramics

1. Different fabrication techniques of
ceramics
By RADWA EL-DESSOUKY
Conventional
powder/slurry
technique
Castable
ceramics
Pressable ceramics
Infiltrated
ceramics
Machinable
ceramics

2. 1.Conventional powder /slurry
technique

3. 1.Conventional powder /slurry technique:
It is the traditional method of forming ceramic prosthesis
and consists of the following steps:
3
1.compounding
2.packing
3.Preheating
4.sintering
5.Surface treatments
6. Porcelain cooling

4. 4
I. Compounding:

5. The process of bringing the particles closer and of
removing the liquid binder is known as condensation.
Dense packing has the following benefits:
Improves substructure of the porcelain & dispense trapped air
(Less porosity)
increase density
Less shrinkage during firing
Enhanced surface texture and strength
2. Packing or condensation:

6. •Condensation steps:
I. Build-up of Cervical Porcelain
II. Build-up of Body Porcelain
III. Cut-back
IV. Build-up of Enamel Porcelain

7. •Condensation methods:
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1-MANUAL
CONDENSATION
2.ULTRASONIC
CONDENSATION

8. •Advantages of ultrasonic
condensation:
8
•Reduces the fluid content of
layered ceramics; resulting in
denser and more vibrant porcelain
mass.
•Enhances translucency and the
shade qualities of the fired ceramic.
•Shrinkage can be reduced to below
5%!
•Time-saving as it reduces the
number of compensatory firing
cycles

9. 9
3.Pre-heating (Drying):
placing the porcelain object on a tray in front of a preheated
furnace at 650C for 5min for low fusing porcelain and at
480C for 8min for high fusing porcelains till reaching the
green or leathery state.

10. 10
•Significance of pre-heating stage:
Ceramic particles held
together in the “green
state” after all liquid has
been dried off
•Removal of excess water
allowing the porcelain object
to gain its green strength.
•Preventing sudden
production of steam that
could result in voids or
fractures.

11. 11
4. Sintering or firing:

The voids are occupied by the atmosphere of the furnace.
 As the sintering of the particles begins, the porcelain particles
bond at their points of contact.
•The sintered glass gradually flows to fill up the air spaces.
•The particles fuse together by sintering forming a continuous
mass, this results in a decrease in volume referred to as firing
shrinkage
• Mechanism of firing:

12. •The gaps between particles become porosities.
• The viscosity of the glass is low enough for it to flow due to its own
surface tension.
The result is that the porosity voids will gradually become rounded
as firing proceeds

12
The voids slowly rise to free surfaces and disappear

13. 13
•Stages of porcelain maturity:
Low bisque Medium bisque High bisque
porcelain surface is quite
porous
Pores still exist on the
surface of porcelain
smooth porcelain surface
porcelain grains begin to
soften and ‘lense’ at their
contact points
The flow of glass grains is
increased. As a
result, any entrapped
furnace atmosphere that
could not escape via the
grain boundaries becomes
trapped and sphere shaped
The flow of glass grains is
further increased, thereby
completely sealing the
surface and presenting
smoothness to the porcelain.
minimal Shrinkage A definite shrinkage is
evident
the fired porcelain body is
extremely weak or friable
The fired porcelain body is
strong and any corrections
by grinding can be made .

14. 1414
•Over-firing:
Due to:
•Firing at above the correct firing temperature Or;
•longer firing time

Effect;
•reduce the strength due to formation of undesirable crystal phases at higher temperature
[de-vitrification]
•increases the chances of slumping [eliminate the shape we made and leave a globule of
ceramic].

•under-firing:
•Effect;
The porcelain object will have a chalky white color overlaying its shade ,Because light is
reflected and scattered at boundaries between particles and at the surfaces of porosity

15. 15

16. •The restoration is tried back to
working cast, often proximal surfaces
need addition (correction).
•Adjustments are made with
diamond stones and discs to treat
seating problems.
•After reaching the desired contour,
occlusion and seating; the
restoration becomes ready for
surface treatment.
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5.Checking fit on the working cast:

17. 17
6. Porcelain surface treatment:

18. 18
•Significance of Glazing:
The aim of glazing is to :
seal the open pores in the surface of fired porcelain ;
minimizing surface roughness and thus controlling
•Aesthetics
• wear
•mechanical properties
•and plaque accumulation

19. A. Natural or Auto-Glaze:
Normally, the porcelain has the
ability to glaze itself by forming a
vitrified layer on the surface of
dental porcelain ceramic
containing a glass phase
B. Applied or Add-on Glaze:
Dental over glazes are composed of clear (colorless) low fusing glass
powder, painted on the fired crown surface; and fired again.
Add-on porcelains: are generally similar to glaze porcelains except
for the addition of opacifier and color pigments .they're exclusively
used for simple corrections of tooth contour or contact points.

20. C. Polishing:
Advantages;
producing smoother less abrasive porcelain surfaces.
Disadvantages;
over polishing can Introduce more surface flaws and
weaken the material.
D. Custom staining (shade modification):
Stains are generally low fusing colored porcelains used
to imitate markings like enamel check lines, calcification
spots, fluoresced areas etc.

21. 6. Porcelain cooling:
21
•It is necessary to cool the mixture fairly quickly.
•If it cools too slowly, crystals form within the glass body which
will degrade its optical properties, turning if from a clear glass into
a cloudy one. Devitrification.
• if it is cooled too quickly, stresses build up in the glass.

• To reduce the stresses ,it is kept near the glass transition
temperature (its solidus) for a long time so that the atoms in the
glass can rearrange just enough to relieve the stress. When most
of the stress has been eliminated, the finished glass is finally
allowed to cool to room temperature [annealing].

22. • Applications of powder/slurry system:
•These ceramics have a great amount of translucency and are
highly esthetic
• used mainly as:
1. veneering layers on stronger cores and frameworks
2.or for making PJCs.
•Examples of systems utilizing this technique:
1.IPS e.max Ceram (Ivoclar-Vivadent)
2. IPS Eris (Ivoclar-Vivadent)
3. Lava Ceram (3M ESPE)
4.Cercon ceram kiss (dentsply)

23. 23

24. 2. Castable ceramics
24

25. 25
• supplied as solid ceramic ingots, which are
heat-treated under controlled conditions
(ceramming) using a lost wax and
centrifugal-casting technique.

•The best known of these systems is Dicor

2. Castable ceramics

26. 1.The die is waxed-up , invested then, burnt-out.
2.The ceramic ingot is heated at 1350 c and casted
using centrifugal casting machine.
3.Ceramming process: the crown is heat-treated at 1075
c for 10 hours resulting in (controlled crystallization)
formation of tiny crystals that are evenly distributed
throughout the body of the glass structure enhancing
its mechanical properties.
4.The final shade of the crown is applied to the surface
of the completed restoration through a complex
reaction between the porcelain and surface stains
• fabrication technique:
26

27. •Advantages of DICOR:
•Highly esthetic: as mica crystals that constitute the
crystal phase closely match the index of refraction to
the surrounding glass phase.
•A one-piece restoration made entirely of the same
material and no opaque substructure exists to impede
light scattering.
•A chameleon effect i.e. the restoration acquires a
part of the color from adjacent teeth and fillings as well
as the underlying cement lute.
•Excellent marginal fit.
•Simple uncomplicated fabrication technique.

28. •Disadvantage of DICOR:
The surface stains may be removed after occlusal
adjustment.

29. 3. Presssable ceramics
29

30. 30
Technique i. The die is waxed-up , invested then, placed in
specialized mold that has an aluminum plunger.
ii. The ceramic ingot is placed under the plunger, heated to
1150C and the plunger presses the molten ceramic into the
mold.

iii. The final shade of the crown is adjusted by staining or
veneering.

31. contains 35 - 45 vol % leucite as crystalline Phase
• Disadvantage:
The presence of about 9% porosity badly affects its flexural strength ,limiting
its use to single unit complete-coverage restorations in the anterior region.
 
Contain 65 vol % lithium disilicate as the main crystalline phase
ADVANTAGE:
it has a much higher flexural strength than that of IPS Empress which makes
it suitable for the usage for fabrication of 3-unit FPDs in the anterior
region, and can extend to the second premolar , due to;

32. 32
•The final microstructure
consists of highly interlocked
lithium disilicate crystals
contributing to strengthening
•About 1% porosity
•Introduced in 2005.
•Considered as an enhanced lithium disilicate press-ceramic
material when compared to Empress II.
•Better physical properties and improved esthetics

33. 33

34. 34
The die is waxed-up to full
anatomical contour
After waxing-up to full
contour, the incisal third of
labial surface is cut-back
The die is waxed-up to minimal
thickness just to support the
tooth shape
1. Wax contouring
2. sprueing
•
Fabrication technique of IPS e.max:

35. 35
3. investing
4. Preheating
The investment ring with the waxed-up die is preheated

36. 36
5. Pressing
The hot completed investment
ring is placed in the hot press
furnace

37. 37
6. After cooling and divesting:
7. finshing

38. I. Staining
technique
The stain paste is mixed with the glaze, applied to the framework
and then, fired

39. 39
II. Cut-back
technique
The veneering technique of
frameworks is performed with
aid of silicon index

40. 40
III. Layering
technique
1. 1
st
Dentin build-up 2. 1
st
Dentin firing cycle
3. compensatory
Dentin build-up

41. 41
technique
• A standard die is scanned
using a mechanical
scanning device and a
computer that turns the
shape of the die into
digitized data.
•The data is then used to fabricate an oversized die [to compensate
for sintering shrinkage ].

•Aluminium oxide powder is compacted onto the enlarged die under
high pressure and then sintered at temperatures above 16000C to full
density thus shrinking it to the correct size and creating a hard core.
• feldspathic porcelain veneer can be applied

42. IN-CERAM
4.Infilterated Ceramics
42

43. supplied as one of the three core ceramics:
1.In-ceram alumina (70 vol % alumina)
2.In-ceram spinnel (contains a mixture of magnesia and
alumina)
3.In-ceram Zirconia (34 vol % alumina +
33 vol % of ceria-stabilized Zirconia)
•Definition:
A porous infrastructure is produced by slip-casting,
sintered, and later infiltrated with a lanthanum-based
glass, producing two interpenetrating continuous
networks, one composed of the glassy phase and the
other being the crystalline infrastructure.
•VITA IN-CERAM , Zahnfabrik :

44. Fabrication
technique
1. Die preparation 2. Mixing aluminous powder with
water to produce slip
3. The slip is painted onto
the die with a brush.
The water is removed by
the capillary action of the
porous gypsum, which
packs the particles into a
rigid porous network
4. sintering

45. 5. lanthanum alumino-silicate
glass is used to fill the pores in
the alumina core.
6. The glass becomes molten and
flows into the pores by capillary
diffusion.
7. Removal of excess glass
8. Veneering with esthetic
veneer [VITA VM7]

46. I. Manually Controlled System or Manual-aided
Design/Manual-aided Manufacturing (MAD/MAM) Method:
5.Machinable ceramics

47. The best-known manual system in the UK is Celay.
Referred to as copy milling, this method is based on the
pantographic principle that was used when making
duplicate keys

48. Computer-aided Design/Computer-aided Manufacturing
II. CAD/CAM

49. They are the systems utilizing a process chain
consisting of scanning, designing and milling
phases.
•CAD-CAM SYSTEMS:
•
Components of CAD-CAM
technology :
1.Scanner = Digitizer
2. CAD Unit = Soft ware
3. CAM Unit = production

50. A. Scanner:
•Function: transform geometry of receptor unit (tooth) into
digital data that can be processed by a computer.

51. 1. Mechanical Scanners:
•Technique:
contact probe with ruby ball at its end maps entire
cast preparation surface line – by - line
• Advantage:
precise but, Less accurate than newer optical
scanning systems.
•Used in: Procera. Scanner, by Nobel Biocare
•Disadvantages:
1. Take long time to scan. 2. expensive.

52. 2.Optical scanners:•Idea:
Triangulation Procedures: Source of light (white, colored
light or laser) + receptor unit are in a definite angle to one
another  through this angle, computer can calculate 3D
data from image on receptor unit.

•Types:
1.Chair-side: fabricate restoration
at chair.
2. Non-chair side: fabricate
restoration in Lab.

53. B. CAD Software:
design the restoration to fit the preparation:
margins,
connectors,
core thickness,
cement gap (internal relief).

54. C. CAM Unit (Production device):
• Function: transform "digital data" to a "product”
•Types: Acc. To No. of milling axes:
3- axis milling device: move in 3- spatial direction (X,Y,Z).

4- axis milling device: more in 3-septial direction + rotatable tension bridge (4
th

axis).
5- axis milling device: move in 3- spatial direction + rotatable tension bridge (4
th
) +
rotating milling spindle (5
th
axis).

Acc ton milling environment:
•Dry milling:  it is done for zirconium oxide low degree of pre-sintering, to avoid
moisture absorption  avoid drying time of zirconium before sintering.
•Wet milling  it is done for metals, composite, silica-based ceramics, zirconium
oxide with high degree of pre-sintering.

55. • Milling strategies:
I- Subtractive Technique from a Solid Block :
•The restoration is cut to contour out of a prefabricated, solid block.
•This technique is used in:
DCS , Cercon and Lava systems
Disadvantage: can create complete shapes effectively, but at the expense of
material being wasted. Approximately 90 percent of a prefabricated block is
removed to create a typical dental restoration.
II- Additive Technique by Applying Material on a Die
•The framework material is applied on a die of a prepared tooth.
•This technique is used in: Procera

56. iii. Solid free form fabrication
•This category includes new technologies originating from the
area of rapid prototyping.
•This technique is used in:
•
•Wax Pro 50 :applies the wax plotter technique, which
works according to the ink jet principle.

57. •Production Concepts
(1) Chair side production:
•Advantages:
i.Save time  only are visit instead of two.
ii.Avoid worrying about improper handling by lab

(2) Laboratory production: Dentist scan preparation and design
restoration then send it to laboratory technician who will mill the
restoration.