1. INVESTING, BURNING-OUT,
CASTING, SANDBLASTING,
PICKLING/ELECTROPOLISHIN
G, FINISHING AND POLISHING
OF FRAMEWORK
Batallones, Brillante, Busto, Cambe, Catibog, R
uffy

2. INVESTING
RUFFY, Mark Ashley

3. BURNING-OUT
BRILLANTE, Charmagne

4. Burning-out
 Method of preparing a mould to receive
casting metal
 Beginning of the elimination of wax
*NOTE: burn out is different from wax
elimination

5. 3 Purposes of burnout:
 It drives off moisture in the mold.
 It vaporizes and thus eliminates the pattern,
leaving a cavity in the mold.
 It expands the mold to compensate for
contraction of the metal n cooling.

6. Materials
 Electric furnace with an adjustable rheostat is
preferred over the gas furnace.
 Casting ring – which is placed into the oven
with the sprue hole down. (this allows the
melted wax to flow out of the main sprue
channel.

7. According to Brumfield...
 The time required to drive off the water is
mainly a function of:
 The amount of heat available.
 The closeness of the heating element to the
investment when placed in the furnace.

8. According to Brumfield...
 The temperature of the mold is held down
during early stages of burn-out by
vaporization of the water.
 At the end of 60 mins, the water is practically
all driven off and the temperature at the inside
of the mold will rise fairly rapidly to near the
temperature of the furnace.

9. According to Brumfield...
 Complete equalization however, requires
another 70 minutes, giving a total burnout time
of two to one and a quarter hours to eliminate
the water and raising the temperature of the
mold approx. 1300 F.
 SOAKING PERIOD- designed to allow time for
the water to be eliminated from the mold and
the mold temperature to rise that of the
furnace.

10. According to Brumfield...
 During the time the water is being
eliminated, the wax is being eliminated
through vaporization and oxidation of carbon.
 Vaporization of wax does not require as much
time as that for vaporization of the water and it
will only require 1000 °F.
 The carbon residue may require more time for
elimination.

11. According to Brumfield...
 It is important to eliminate all the moisture
because:
 The casting would be porous because of the
continued emission of steam by the investment.
 The venting of the mold cavity is largely
accomplished through the interstices of the
investment itself

12. According to Brumfield...
 Steam will then carry the heat into the
investment during the early stages of the
burnout (if the investment is not burned out on
the same day it is poured, it should be soaked
in water for few minutes before it is placed in
the burnout furnace).
 The mold should be placed in the casting
machine first to balance the weight against the
weight of the mold.

13. Procedure
1. Prepare and balance the casting machine
before the casting ring is placed in the burnout
oven.
 Ifthe machine is not an electric melt type, a fresh
strip of asbestos should be adapted to the large
ceramic crucible.
a. Cut the strip slightly longer than the crucible.
b. Taper one end.
c. Wet the liner.

16. Procedure
d. Funnel is made at tapered end.
e. Funnelled end is pushed through spout of
crucible.
f. Main portion of liner is adapted inside the
crucible.
g. Funneled end is adapted to inside of spout with
instrument to form liner for spout.
h. Completed liner in crucible.
i. Lined crucible, metal and invested partial
denture are placed in casting machine and then
it is balanced.

19. Procedure
2. Soak the investment in water for several
minutes.
3. Place the ring in a cool furnace sprue side
down.
4. Turn the burnout furnace on and adjust it to
reach 1000°F in about 1 hour.
5. Leave the furnace at 1000°F setting for 2
hours. Then increase the temperature so it will
hold temperature Between 1250°F and
1300°F.

23. Procedure
6. When the temperature of the furnace has
reached 1250°F the mold must heat soak at
this temperature for at least 1-1.2 hours (to
completely remove the moisture or carbon
residue from the interstices or space of the
investment).

24. Procedure
7. The mold is ready to cast.
 Invested pattern is removed from the burnout
oven following complete elimination of the wax
pattern.
 investment mold is placed into the casting
machine.
*The time it takes for the invested pattern to
undergo complete burnout is 3 ½ to 4 hours.

25. Burnout furnace
is widely used in
dental
laboratories for
the wax
elimination of
casting rings and
preheating
crucibles.

26. CASTING
CAMBE, Estephanie Mae

27. Casting
 A manufacturing process wherein a liquid
material is poured into a mold that contains a
hollow cavity of a certain shape or figure and
then allowed to set and solidify.
 The solidified part you obtain is called the
casting which is removed from the mold once
completely solidified.

28. Casting
 All methods use force to inject quickly the
molten metal into the mold cavity.
 Centrifugal, steam, air pressure force.
 Too much or too little force is undesirable.
 If too little force is used, the mold is
completely filled before the metal begins to
freeze.
 If too much force is used, excessive
turbulence may result in the entrapment of
gases in the casting.

29. Casting
 Centrifugal casting machines is regulated by
number of turns put on the actuating spring.
 The metal may be melted with a gas-oxygen
blowtorch or by an electric muffle surrounding
the metal.
 Induction method provides a rapid and
accurate method of melting the metal.

30. Induction casting
machine
The alloy (arrow) is
placed pinto a clean
crucible

31. Procedure
1. Examine the liner in the crucible to see i it is
clean and continuous to and through the
spout.
2. Wind the casting machine three or four turns
depending on the tightness of the
spring, and lock it in position.
3. Place the metal in the crucible on the
asbestos liner

33. Procedure
4. Light the torch and adjust it to form a
reducing flame.
5. Heat the metal , keeping the tip of the blue
cone on the surface of the metal. A large
bulk of metal takes several minutes to melt.
When the metal begins to ball up, add
powdered flux.
6. When the surface of the metal is clean, and
a swirling action can be seen, position the
casting ring in the casting machine. Do not
move the flame from the metal.

36. Procedure
7. Ifthe metal surface is still clean and the metal
is swirling action can be seen, position the
casting machine to drop the locking pin.
Without moving the flame from the metal,
release the casting machine.

37. 8. When the casting machine stops, remove the
ring and allow the mold to bench cool until
the red sprue button has become somewhat
blackish. Cooling of the mold depends on
the flask
Ney partial denture flask – a cooling period
of 8-12 minutes is sufficient
Kerr or Jelenko flask – it is suggested that
20 mins be allowed for bench cooling to
avoid the possibility that the casting will be
too soft

38. Recovering the casting
After the casting is completed, allow the mold to
cool until the sprue button has changed in
color from red to black when viewed in shaded
light. This will about 8 to 12 minute after
completion of a large casting.
At this time, quench the hot ring in water. With
most gold castings this will produce a fairly
soft and ductile condition in the metal and will
make the finishing much easier.

40. Recovering the Casting
 The process of allowing the casting to cool slowly
in the mold for a controlled period of time and then
quenching is known as heat hardening the alloy.
 After the metal has been finished, but before it is
polished, the properties of metal should be
restored. This is known as heat hardening the
metal.
 The process is done by simply most simply by
placing the metal framework in an oven that has
been heated for 845 degrees Fahrenheit (450 C)
and permitting it to cool to 482 degrees(250 C)
Fahrenheit over a period of 30 mins. After, it is
removed from the furnace and again allowed to
bench cool with the metal at its hardened state.

41. SANDBLASTING
CATIBOG, Lara Patricia

42. Sandblasting
 Process wherein a hard surface is
smoothened, shaped, and etched.
 It can be done using a high speed sandblaster.
 It can occur:
 Naturally as a result of a particle blown by the
wind causing erosion.
 Artificially using compressed air.

43. Sandblasting
 Most common medium for sandblasting is
dentistry is aluminium oxide. The fine
aluminium oxides are recycled within the
sandblasting machine and replaced after 30-
40 minutes of total accumulated operation
time.
 60-80 psi of force is exerted by the machine.

44. Purpose of sandblasting
 Used to clean a surface of anything that may
be clinging to it or remove impurities that are
attached to the metal framework and prepare
the surfaces for subsequent stoning and
polishing.
 Provide mechanical retention between
porcelain-metal.
 Removing the casting oxides as well as
proper sandblasting of the alloy with 100-150
microns aluminum oxide results to
mechanical bonding.

45. Purpose of sandblasting
 Micromechanical retention of denture base to
RPD framework.
 Mechanical retention are provided by the
lattice, mesh, beads, and posts.
 There is a low bond strength between the
resin and metal that can lead to
microleakage, discoloration, and breakage.

46. Uses of sandblasting
 Used to clean a surface of the metal
framework.
 Removes stone particles around the teeth and
from the resin-metal joints.
 Removes impurities that is attached to
framework.

47. Artificial Sandblasting
 Patented by Benjamin Chew Tilghman on October
18, 1870.
 By the use of compressed air.
 Sand was sieved to a uniform size.
 The silica dust produced in the sandblasting
process can yield to silicosis.
 A chronic lung disease due to continuous inhalation of
silica dust particle.
 However, this may be prevented by using protective
clothing and breathing air supply.
 Alternatives to sand are glass beads, metal
pellets, dry ice, powdered abrasives of various
fineness and ground coconut shells.

48. Alternate Abrasives
 Glass beads
 Metal pellets
 Dry ice
 Powder abrasives of various forms
 Ground coconut shells

49. Parts of Sandblasting machine
 Abrasives
 Air compressor
 Blaster gun

50. Types of Sandblaster machines
 Automatic
Sandblaster –
machines that
eliminate the use of
manual movement
of either the shot
stream of the
workpiece, but rely
on mechanical
means to supply
these features.

51. Types of Sandblaster machines
 Blast Cabinets –
enclosures in which
items are placed to
be abraded. Useful
in containing the
blasting operation
and preventing
exposure of the
blasting media to
surrounding
workers.

52. Cleaning of the Casting
1. After casting has been made the ring is removed
and allowed to bench cool for 10 minutes before
it is plunged into the water, this will temper the
casting. Then the casting is removed from the
ring, freed of excess investment and cleaned
carefully with a stiff brush under a steam of
water.
2. The casting should not be struck and pried with
metallic instrument as to not dislodge the
investment.
3. Most of the investment, except for small
particles difficult to reach can be removed with

53. Procedure of Sandblasting
1. A stream of air filled with particles of walnut
shell or particles of sand is blown from a
nozzle under pressure.
2. The casting rotated so that the stream of the
air is directed towards those areas that
contain the remaining particles of investment.
3. The operator blasts the parts from the outside
of the cabinet by placing his arms in gloves
attached to glove holes on the cabinet
viewing the part through a window, turning
the blast on and off using a foot pedal.

54. Procedure of Sandblasting
4. The sand is projected by compressed air
through a fine nozzle onto the casting and
these high speed silica particles abrade the
surface of the casting and break away any
debris.
5. Sandblasters propel abrasive grits through a
nozzle at high velocity in a steam of
compressed air.
6. Sandblasters clean off residual investment
materials to prepare metal surfaces for
further treatment.

55. Procedure of Sandblasting
7. Dust extraction systems keep the abrasive
grit in the container; this can re-circulate back
through blasting nozzle.
 Recirculation can degrade the grit rapidly and it
can become much less effective; the best and
strongest bonds are formed when fresh grit is
used.
 Various grades of grit can be used. The finest
grits will almost polish the surface of cast gold
restorations and are very useful in finishing
techniques.

56. Sandblasting VS Shellblasting
 Sandblasting
 Used for harder
metal like cobalt—
chromium.
 Uses zircon grit,
silica sand, or
aluminum oxide as
an abrasive.
 Never be used on
acrylic or porcelain
because it will ruin
them.

57. Sandblasting VS Shellblasting
 Shellblasting
 Used for softer
metal like gold.
 Uses crushed
walnut shells as
abrasives.
 Walnut shells do not
affect the teeth or
denture base.

58. PICKLING/ELECTROPOLIS
HING
BATALLONES, Amery Rose

59. Pickling
 Pickling is the process in which a piece of
metal (casting) is placed in an acid bath to
remove surface oxides, investments particles
and other contaminants from the surface of the
metal framework.
 Goldalloy pickling
 Cobalt-chromium Electro polishing

60. Materials
 Stove
 Water
 Heat-resistant porcelain dish or glass beaker
 Pickling solution (50% hydrochloric acid or
50% sulfuric acid (Jel-pac, Prevox))
 Plastic tongs

61. Procedure
1. Place the casting in a clean high-resistant
porcelain dish then, pour the clean pickling
solution to a depth just enough to cover the
casting.
2. Warm gently the pickling solution, until the
surface of the metal brightens and show of
development of a characteristic gold luster. The
solution should not be boiled. Effective cleaning
of the solution is accomplished before the boiling
temperature is reached.
3. Remove the casting from the solution with plastic
tongs.
4. Pickling solution is poured off (flushing
generously with water or base solution) and the
casting is washed with an abundance of water.

62. Disadvantage of boiling or
prolonged heating of the acid
solution
1. Acid fumes may be harmful and damaging.
2. May corrode the laboratory equipment and
instruments.

63. Precautions to be taken while
pickling
1. It is highly recommended to use the pickling solution be acquired
from the alloy supplier.
2. Never heat the gold cast directly in a flame prior to immersing
it in pickling solution.
3. Casting should not be heated and dropped into the pickling
solution.
4. Metal or stainless steel tong should not be used to remove
castings from the pickling solution.
5. Since only small quantity is solution is needed (10ml), new
pickling solution can be used each time to avoid excessive
contamination. It should be clean and non-corrosive to
laboratory equipments and instruments, relatively colorless
rather than have the typical greenish blue color of
contaminated acid.

64. Electropolishing
 Electro polishing is an electro-chemical process in
which a metal is placed in an electrolytic solution
and an electric current passes through it. Very
minute particles on the surface of the metal
framework are removed by electrolysis, in turn
leaving a polished surface.
 It is used to polish, passivate, and deburr metal
parts.
 Used for Cobalt Chromium
 Main electrolyte: Glycolic Acid (Glycerin)
 12Volts
 Temperature: 18-20 degree Celsius

65. Electropolisher

66. Procedure:
Metal framework Electrolyte bath: 4-
Electrolyte temp:
attached to anode 5cm from the
18-20C
of 12V rectifier cathode
Rectifier: OFF 5 mins – leaving
remove framework framerwork
Rectifier: ON
& wash under immersed in
running water polishing bath
Remove the
5 mins - Lightly dry Rinse under
framework fro the
& immerse again running water
electrolyte bath

67. Advantages of electropolishing
1. Improve corrosive resistance of the metal
framework.
2. Better surface finish.
3. Ease of cleaning of the framework.
4. Reduces the microscopic crevices in which
bacteria can propagate and tiny particles can
accumulate.

68. FINISHING AND POLISHING
FRAMEWORK
BUSTO, Treblig Earl

69. Finishing and Polishing
 Smoothing the cast framework with
progressively finer abrasive agents to remove
scratches and to give a high luster to the
completed framework.
 After grinding, the prosthesis must be in a:
 Completely smooth state.
 Required on areas contacting the teeth and soft
tissue.
 Highly polished condition.
 Includes
external surfaces such as clasp arms, rest
and major connector.

70. Purpose
 Maintain cleanliness of appliance while in the
oral cavity.
 Maintain health and cleanliness of the oral
cavity.
 Roughed surfaces will rapidly collect food
debris, plaque and calculus.
 To ensure the frameworks fit the working cast
and natural dentition accurately.

71. Finishing of framework
 Cutting is done by the abrasive wheels or points
and the speed of lathe or handpiece.
 Cobalt chromium alloy uses high speed lathes
(24,000 rpm).
 The bur or stone must be locked in the chuck with
no more than 2cms ticking out.
 Reinforced mandrel should be used to prevent
shaft from bending or breaking.
 Heatless stone and disks should be held more
than 1cm from the chuck.
 Avoid the use of heavy pressure not only for
safety’s sake but because it will
unnecessarily heat the casting, causing it to warp.

72. High speed lathe

73. The bur or stone must be locked in the chuck with
no more than 2cms ticking out.

74. This will happen if the bur is
chucked too far.

76. Rules of finishing the casting
 High speeds are preferable to low speeds.
 In
an experienced hand, there is less danger of
the casting being caught and thrown out of the
hands by the rotating instrument.
 The wheels or points and the speed of their
rotation should do the cutting.
 Excessive pressure heats the work, crushes the
abrasive particles, causes the wheels to clog and
glaze, and slows the cutting.
 A definite sequence for finishing should be
adopted and followed for every framework.

77. Rules of finishing the casting
 Clean polishing wheels should be used.
 Ifcontaminated wheels are used, foreign particles
may become embedded in the surface, which will
lead to discoloration.
 Be sure that each finishing operation
completely removes all scratches left by the
preceding one.
 Remember that each successive finishing steps
uses a finer abrasive and therefore cuts more
slowly and requires more time to accomplish.

78. Procedure
1. Cut the sprue from the casting with a
separating disk. Make the cut as close to the bar
as possible, but do not nick or damage the
framework.
 When framework is made up of gold, use a
jeweler’s saw to save gold and prevent accidental
cutting.

80. Procedures
 2. Grind off the sprue stumps with 7/8 inch
stone(heatless stone). Restore the original
shape of the part of the casting to which the
sprue is attached.

81. Procedures
3. Using a disk, barrel-shaped mounted
stone, fine tapered mounted stone, or carbide
bur, depending on the access to the
area, remove the flash from the clasp
arms, minor connector, rests, indirect
retainers, and denture base retention areas.
 Mounted stones for grinding cannot be used
interchangeably.
 For Gold- too soft, it may disintegrate rapidly when
used on cobalt chormium.
 For Cobalt chromium- it is too hard for gold, may clod
up with soft metal and will not cut.

83. Procedures
4. Use larger wheels or stones to smooth the
contour of the major connector and to remove
small pits or defects. The stone should be kept
moving forward and backward along the major
connector in strokes at least 15mm long to avoid
creating small depressions, waves or uneven
surfaces of the contour.
 Cross grinding can weaken the bar when grinding
on a thin spot or parts.

85. Procedures
5. Smooth the rest of the framework except for
those areas which come in contact with the teeth
with a fine tapered mounted stone. Use this
stone also to slightly round the sharp edges of
the inferior border of the clasp arms.

87. Procedures
6. Use an inverted cone stone or a separating
disk to refine the undercut but joint of the finish
line, both internally and externally. A wire brush
is excellent for brightening nailhead.

90. Procedures
 7. Optionally a series of sandpaper disks of
decreasing grit can be used to smooth all
clasp arms and occlusal rest. (Cannot be used
on cobalt chromium castings).
 Rubber abrasive wheels, knife edge
wheels, disks, and points are preferred for fine
finishing on the castings.
 For gold- with fine pumice
 For Cobalt chromium- with carborandum

93. Procedures
8. Finish the metal surfaces that contact the teeth next.
a) Remove the nodules, small defects and irregularities with
fine stones or burs.
b) Shape a rubber abrasive point by running it against a truing
stone or a heatless stone until it comes to a point.
c) Using a cylindrical felt cone with Tripoli, produce a
completely smooth surface.
a) Hallow out the end of the cone using the tip of the knife to be
used to polish the underside of occlusal rest
b) After polishing with Tripoli, wash using soap and water, a
mixture of 2/3 tincture of green soap 1/3 household ammonia,
or a ready to use septisol solution.
d) Use another flat cylinder with jeweler's rouge to complete
the finishing.

94. Removal of nodules

95. Removal of nodules

96. Shape a rubber abrasive point by
running it against a truing stone

97. Use a cylindrical felt cone with
Tripoli

98. Hallow out end of the cone

99. Wash

100. Use another flat cylinder with
jeweler's rouge to complete the
finishing.

101. Procedures
9. Smooth the entire remaining framework,
except the clasp arms, using the rubber wheels
and points.
 Run the wheel parallel to the length of the major
connector.
 Use knife edge wheel on finish lines

103. Procedures
10. Use small felt wheels the Tripoli next to
remove traces of marks left by the rubber wheels
and points on some of the more difficult to reach
areas.

105. Procedures
11. The entire framework including the outer
surfaces of the clasp is polished with a small
Tripoli-impregnated cloth wheel.
a) Polish the clasp arms with the cloth wheel
running parallel to the length of the clasp
from shoulder to the tip.
b) Polish all other areas of the framework from
several different directions to produce an
even polished surface.

107. Tripoli impregnated cloth wheel
 Used in lathe
 Must be ―broken in‖ to make it softer, fluffier
and to remove small strings
 Use a dull-edge knife on a revolving cloth
 Burn off strands
 Use a cloth for tripoli, and a cloth for the rouge

109. Procedures
12. After the casting has been thoroughly
polished with tripoli, scrub the casting with
soap, water and a brush. Remove all traces of
tripoli.

111. Procedures
 13. Heat-treat the casting following the
manufacturer’s directions because different
alloys are heat-treated in various ways.
 14. After heat treatment, it will be necessary to
pickle and repolish the casting with tripoli.

112.  15. Polish the framework with a cloth wheel
and rouge.

114. Procedures
16. Scrub the casting with soap and water or
tincture of green soap and ammonia and if
necessary, chloroform to remove all traces of the
rouge.

115. Procedures
17. Dry the casting thoroughly with compressed
air and examine it carefully under bright light and
magnification for any scratches or defects.

117. Procedures
18. If the polish is satisfactory, the framework
may now be tried on the master cast or duplicate
master cast.
19. If the block – pout and relief wax is to be
removes it may be done by soaking the cast in
warm (120 F; 49 C) slurry water for 5 minutes
the pouring hot (200 F; 95 C) slurry water over
the cast to remove the wax.
20. Check the fit of framework on the master
cast.

118. Procedures

119. Problems with finishing and
polishing