LECTURE 16: LABORATORY PROCEDURES Flashcards
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DESIGN TRANSFER FROM DIAGNOSTIC CAST
without removing the master cast from the survey table or changing the tilt, the technician transfers the design from the diagnostic cast to the master cast with extreme care and clearly marked to avoid confusion
→ design should mimic the design on diagnostic cast
T
the simplest and traditionally used for recording of the final orientation of the cast on the surveyor
RETRIPODING THE MASTER CASTS
the primary cast is mounted on a surveying table and a carbon marker is used to contact three points of the cast
RETRIPODING THE MASTER CASTS
In MARKING THE HEIGHT OF CONTOUR , marking the greatest _______ of the tooth
convexity
MARKING THE HEIGHT OF CONTOUR, determines if the tooth has an adequate ______ area
retention
“survey line”
MARKING THE HEIGHT OF CONTOUR
→ scraping the outline of the major connector into the master cast
→ ensures intimate contact of the major connector with the palatal
tissues
→ reduce the packing of food particles underneath the major
connector
BEADING OF THE MAXILLARY MAJOR CONNECTOR
treating the master cast with a surface sealer using a brush or an aerosol spray to seal the cast and protect the design during the other steps of cast preparation and duplication
SPRAYING
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In SPRAYING for the PREPARATION OF MASTER CAST
sealer application should be done in front of a suction vent because inhaling aerosol is potentially dangerous
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elimination of undesirable undercuts on the master cast with wax is commonly referred to as ____
blocking out
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both hard and soft tissue areas will require block out
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proximal tooth surfaces used as guiding planes
A. parallel block out
B. shaped blockout
C. arbitrary blockout
A
beneath all minor connectors
A. parallel block out
B. shaped blockout
C. arbitrary blockout
A
tissue undercuts to be crossed by rigid connectors
A. parallel block out
B. shaped blockout
C. arbitrary blockout
A
tissue undercuts to be crossed by origin clasps
A. parallel block out
B. shaped blockout
C. arbitrary blockout
A
on buccal and lingual surfaces to locate plastic or wax patterns for clasp arms
A. parallel block out
B. shaped blockout
C. arbitrary blockout
B
all gingival crevices
A. parallel block out
B. shaped blockout
C. arbitrary blockout
C
gross tissue undercuts situated below areas involved in design of
denture framework
A. parallel block out
B. shaped blockout
C. arbitrary blockout
C
tissue cuts distal to cast framework
A. parallel block out
B. shaped blockout
C. arbitrary blockout
C
labial and buccal tooth and tissue undercuts not involved in
denture design
A. parallel block out
B. shaped blockout
C. arbitrary blockout
C
beneath lingual bar connectors or the bar portion of the linguoplates when indicated
RELIEF
retentive meshwork must be raised above the edentulous area to allow resin to completely surround it
RELIEF
RELIEF
at least ___ mm of resin should surround the tissue surface of the mesh
1
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RELIEF
the finish line should be sharply defined
T
→ areas in which major connectors will contact thin tissue, such as hard areas so frequently found on lingual or mandibular ridges and elevated palatal raphes
→ beneath framework extensions onto ridge areas for attachment of resin bases
RELIEF
TISSUE STOP
→ a small square of ____ mm of relief wax is removed at the distal end of the saddle
2x2
it provides stability of the framework during acrylic metal processing
TISSUE STOP
______ can better support and restrict the material; can also prevent it from over covering the tissue surface
tissue stops
PREPARATION OF MASTER CAST
- DESIGN TRANSFER FROM DIAGNOSTIC CAST
- RETRIPODING THE MASTER CASTS
- MARKING THE HEIGHT OF CONTOUR
- BEADING OF THE MAXILLARY MAJOR CONNECTOR
- SPRAYING
- BLOCK OUT
- RELIEF
- TISSUE STOP
INVESTMENT MATERIALS
→ there are three types:
o gypsum bonded
o phosphate bonded
o silica bonded
“low heat investments” are used for casting Type IV partial denture gold and ticonium
A. gypsum bonded
B. phosphate bonded
C. silica bonded
A
refractory materials are used for chrome cobalt alloys, titanium and titanium alloys are termed ____
“high-heat investments”
composed of a mixture of silica (SiO2) and calcium sulphate
hemihydrates
A. gypsum bonded
B. phosphate bonded
C. silica bonded
A
thermal expansion type; for casting inlays and crowns
Type 1
2
3
Type 1
(GYPSUM BONDED)
hygroscopic expansion type; for casting inlays and crowns
Type 1
2
3
2
(GYPSUM BONDED)
casting complete and partial dentures
Type 1
2
3
3
(GYPSUM BONDED)
powder contains silica, magnesium oxide and ammonium phosphate
A. gypsum bonded
B. phosphate bonded
C. silica bonded
B
can be mixed with water or colloidal silica
A. gypsum bonded
B. phosphate bonded
C. silica bonded
B
for inlays, crowns and other fixed restorations
Type 1
2
3
1
(PHOSPHATE BONDED)
for partial dentures and other cast removable restorations
Type 1
2
3
2
(PHOSPHATE BONDED)
consists of powdered quarts or cristobalite which is bonded together with silica gel or ethyl silicate
A. gypsum bonded
B. phosphate bonded
C. silica bonded
C
used for high fusing alloys
A. gypsum bonded
B. phosphate bonded
C. silica bonded
C
DESIGN TRANSFER
before the waxing begins, design must be transferred again from the master cast to the ____ cast
refractory
master cast is evaluated and the outline of framework design is transferred precisely to refractory cast
DESIGN TRANSFER
plastic patterns are glued to the cast with a mixture of acetone
and plastic pattern scraps mixed to a watery consistency
WAXING TECHNIQUE
- What technique?
→ tacky liquid is painted on the design outline with a fine brush
and allowed to dry for a few seconds
→ patterns are carefully adapted to the cast with the help of a
soft rubber pencil eraser shaped into a 2. _____
- WAXING TECHNIQUE
- wedge
the areas where the retentive meshwork joins the major
connector must be reinforced
WAXING TECHNIQUE
____ is attaching wax or plastic form to the wax pattern, to provide an entrance to the mold space and to serve as a reservoir of metal during the casting procedure
spruing
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rules of SPRUING:
o sprues should be large enough
o sprues should lead into the molten cavity as directly as
possible
o sprues should be attached to the wax pattern at its bulkier
sections
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SPRUING
preferred for complete denture metal bases
A. Single
B. Multiple
A
SPRUING
majority of partial denture castings
A. Single
B. Multiple
B
a cone shaped plastic sprue is attached to the central sprue from which auxiliary sprues run to each corner of the wax pattern
top spruing
this provides the strength necessary to resist forces created by the stream of molten metal
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
A
→ to make a smooth surface of the mold cavity so that the casting obtained will require as little as finishing required
→ to establish an avenue of release for the gases created by burnout and casting procedures
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
A
to compensate for the dimensional changes that occur when the metal goes from the molten to the solid state
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
A
the time and temperature required to eliminate wax from the mold cavity is specific to the refractory-alloy system that is being used
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
B
expands the mold to compensate for contraction of the metal during cooling
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
B
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steps:
o should be dry at the start of the burnout cycle; steam will then carry the heat into the investment during the early stages of the burnout
steps:
o should be MOIST at the start of the burnout cycle; steam will then carry the heat into the investment during the early stages of the burnout
mold should be placed in the oven with the sprue hole down
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
B
o should start with a cold oven
o temperature should be increased slowly and be maintained
o when the cycle is complete, all of the wax pattern is eliminated
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
B
→ if little force is used, the mold is not completely filled before the metal begins to freeze
→ if excess force is used, turbulence may result in the entrapment of gasses in the casting
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
B
______ is the method of choice for base metal alloys
induction casting
→ mold is removed from the machine and allowed to cool accordingly
→ at the appropriate time, the mold is broken by tapping it with 2. _____ to break off the outer layer of investment
→ remaining investment is then removed by 3. ___ blasting
→ if not removed, may cause tarnish and corrosion
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
- C
- wooden mallet
- sand
rubber wheels, rubber points, knife edge wheels
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
D
→ magnification and bright light for defects
→ point is formed on truing stone or heatless stone
→ separating disk to cut sprue
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
D
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major connector finished with abrasive stones
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→ remove nodules from latticework
→ felt cylinder used with Tripoli on surfaces that contact teeth
→ felt wheel to polish tissue side and tongue side of major
connector
→ knife edge wheels for finish line
→ rag wheel with Tripoli to polish rest of framework
→ scrub casting to remove tripoli
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
D
______ on cotton can be used to remove last traces of tripoli
chloroform
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the technician begins to fit the framework by carefully seating the casting on the master cast and attempts to identify the first spots that bind
T
→ as the retentive clasp tip engages an undercut area, they will most likely be the first area that binds
→ technician must carefully relieve the cast in the area of the clasp tip undercuts to allow the clasps to pass the height of contour
→ some technician bend the retentive clasp arms away from the cast and then attempt to recontour the clasp back into contact
A. INVESTING THE REFRACTORY CAST
B. BURNOUT
C. RECOVERY OF CASTING
D. FINISHING THE FRAMEWORK
E. FITTING THE FRAMEWORK
E