INTRODUCTION- Removable partial denture: the replacement of missing teeth and supporting tissues with a prosthesis designed to be removed by the wearer-GPT. Cast partial denture is a type of partial denture comprising a cast metal framework with acrylic resin prosthetic teeth. Traditional acrylic partial dentures are less durable, retentive, and stronger than cast partial dentures.

1. Department of
prosthodontic
s
TOPIC- Lab procedures in Cast
Partial Denture.
Guided by- Dr. Sonal Pamecha

2. Introduction
 Removable partial denture: the
replacement of missing teeth and
supporting tissues with a prosthesis
designed to be removed by the
wearer-GPT.
 Cast partial denture is a type of
partial denture comprising a cast
metal framework with acrylic resin
prosthetic teeth.
 Traditional acrylic partial dentures are
less durable, retentive, and stronger
than cast partial dentures.

3. LAB PROCEDURES
 Care of impression & making casts.
 Pouring corrected cast impressions
 Stock and custom impression trays.
 Record bases & mounting casts.
 Survey & design.
 Design transfer, blockout , relief &
beading.
 Duplication and refractory casts.
 Waxing & spruing.
 Investing, burnout & casting.
 Finishing & polishing in framework.
 Selecting & arranging teeth.
 Flasking, processig, deflasking &
finishing.

4. I. CARE OF
IMPRESSIONS &
MAKING CASTS
 Some restorations are made to fit patient
directly and few are made to fit the cast.
 If the cast is not accurate the restoration
cannot possibly fit patient satisfactorily.
Essentials for casts
 All surfaces to be contacted by the
prosthesis should be accurate & free
of voids/nodules.
 Removel of nodules resulting from
voids/bubbles in the impression is
essential, but hand carving in critical
areas is, of course, not acceptable.
 The cast extensions should include
all of the area available for denture
support, for example, 3-4 mm
beyond the hamular notches on the
maxillary cast & 3-4 mm beyond the
re tromolar pad on the mandibular
cast.

5. Alginate impressions
1. Examining the impression.
2. Care of impression.
3. Pouring the cast.
4. Trimming the cast.
II. POURING CORRECTED
CAST IMPRESSION
 The 4 techniques for pouring
corrected cast impressions are
boxing with a:
 Plaster pumice- mix & wax
 Beading and boxing with wax
 Beading with wax & 2 stage pour
 North Carolina technique

6. BEADING & BOXING
WITH WAX
 Beading & boxing the corrected
cast impression with wax works
well for zinc oxide eugenol paste/
plaster of paris impressions.
Beading & boxing with wax & 2
stage pour
 Beading the corrected cast
impression with wax & 2 stage
pour procedure is similar to
beading & boxing procedure with
wax.
 It can be used for metallic paste or
plaster of paris impression.

7. III. STOCK & CUSTOM
IMPRESSION TRAYS
 Custom trays are usually made acrylic
resin trays.
 The tray materials are usually not
applied directly over the cast.
 Spacing material such as a wax or tin
foil substitue is used so as to provide
relief for the impression material when
the impression is removed from an
undercut.
 For alginate relief should be one-forth
inch ( 0.6 cm) & for elastomeric
materials a thickness of one-eighth
inch (0.3 cm) is necessary

8. STEPS-
o Outline of relief is
drawn on the cast.
o Even layer of wax is
applied to cast &
painted with tin foil
substitute.
o Tray formers are
lubricated with
petroleum jelly.
o Fluid resin mix is
poured into a
lubricating mould.
o Acrylic resin in mould
must set until it
becomes plastic &
can be handled.

9. o The plastic
baseplate is
centered over the
cast & the entire
outline marked is
covered.
o Plastic baseplate is
adapted onto the
cast.
o Before the material
sets some of the
excess is added to
form the handle.
o Tray separated
cleanly from cast &
wax relief when tin
foil substitute is
used.
o Tray trimmed
accordingly. Borders
are rounded off and
tray is perforated by
round bur

10. IV. RECORD BASE &
MOUNTING CAST
RECORD BASE REQUIREMENTS:
 Same adaptation to basal seat area
as finished denture base.
 Same border form as finished
denture base.
 Sufficient rigidity to withstand
occlusal forces.
 Dimensional stability.
 Construction that permits use as
base for teeth arrangement.
 Easy, quick, and inexpensive
fabrication & desirable color.

11. Method of fabrication of
record base
 Autopolymerizing record base
◦ Sprinkle on method
◦ Sprinkle on method with framework
◦ Finger adapted dough method
◦ Wax confined dough method
 Shellac record base
 Stabilized shellac record base
◦ Stabilised with zinc oxide eugenol
paste
◦ Stabilised with elastomeric
impression material
◦ Stabilised with autopolymerising
resin.
◦ Vaccum adapted thermoplastic resin
base
◦ Wax record base
◦ Visible light cured record base

12. V. SURVEY AND DESIGN
 Principles of surveying-
 Surveying is the procedure of
studying the relative parallelism or
lack of parallelism of teeth &
associated structure so as to select a
path of placement for a restoration
that will encounter the least tooth or
tissue interference & that will provide
adequate and balanced retention.
Objectives of surveying:
 To locate & evaluate hard & soft
tissues undercuts on the cast &
based on evaluation, select a path of
insertion that will make optimal use of
favorable undercuts will minimising
effect of unfavourable undercut.

13. Surveyor
 Mechanical devices that permits
placement of cast in selected fixed
position while instrument is used to
first analyze & then mark the
undercuts on the cast.
PARTS OF SURVEYOR:

14. VI. DESIGN TRANSFER,
BLOCKOUT, RELIEF &
BEADING
DESIGN TRANSFER
If designed diagnostic casts
accompany the master cast to lab,
metallic portion of design on diagnostic
casts will be transferred to master cast.
Procedure- examine the master casts
to determine acceptability. If acceptable
the cast should be examined for
nodules that must be removed.

15. • Place 3 widely separated marks on
the diagnostic casts.
• Mark 3 spots on master cast in
exactly same place as on the
diagnostic cast.
• Using the carbon marker in
surveyor, mark survey lines on
master cast.
• Using the diagnostic cast as a guide,
draw the metallic portion of design
on the master cast with a brown
pencil & resin finish lines with blue
pencil.
• The design on master cast should
be same as design on the diagnostic

16. Blockout & duplication
 Preparing cast for duplication.
 Cast are blocked out to eliminate
undercut areas on the master cast
that will be crossed by rigid parts of
partial denture.
 All parts of framework, except the
retentive clasp tips, are non flexible &
will not spring into an undercut.
 Additional area to be blocked
out,which are eliminated for
convenience include:
 Ledges on which clasp patterns will
be placed.
 Beneath connectors to avoid soft
tissue impingement.
 To provide for later attachment of the
denture base to the framework.

17. Beading
 Beading on the borders of maxillary
major connectors surveys to prevent
food particles from collecting beneath
the framework & producing discomfort
for the patient.
 Beading is accomplished with a small
spoon excavator by scraping the cast
along the anterior & posterior borders of
major connector.
 Beading depth should not exceed 1mm.
It should fade out as the gingival margins
are approached or as prominent area in
the midline of the palate.

18.  Prepared master casts are
duplicated to produce an
exact copy of the master cast
in investment material. This
cast is called the refractory
cast because it contains
ceramic material that permits
it to withstand burnout
temperature of about 1300
degree F( 704 degree C).
 The framework pattern is
formed on the refractory cast
using the wax and plastic.
After the framework wax-up is
complete, it is invested,
burned out, and cast to
produce the metal framework.
VII. DUPLICATION &
REFRACTORY CASTS

19. Procedure
 The master cast must be thoroughly
soaked in clear slurry water. A minimum
of 30 minutes soaking is usually
required.
 When the color in the entire cast has
changed, it is an indication that the cast
is thoroughly soaked.
 If a cast is completely submerged in
water, it will require 5 to 8 hours to soak
all the way through.
Investment cast
 Most gold alloys are cast into gypsum
bound silica investment.
 Cobalt chromium alloys that solidify at a
temperature of about 1300 degree C
also use a gypsum binder.
 These are usually referred to a
phosphates bound investments, and
they are also used with high fusing gold
and other alloys to which porcelain is
fused.

20. VIII. WAXING & SPRUING
 After the master cast is duplicated to
make a refractory cast, it is
necessary to transfer the design to
the refractory cast and complete the
wax pattern.
Waxing the maxillary cast
procedure:

21.  There are four main types of
retention:
1. beads or nailheads
2. open retention without relief
3. open retention or mesh with
relief, and
4. all metal base with or
without tube teeth, without
relief.

22. Waxing the mandibular
cast
 Study the framework design that
was transferred from the master
cast. The most critical point of the
transfer is the lingual bar.
 The superior margin of the bar
must not be placed closer than 3
mm to the gingival margin of the
teeth.
 Also, it must not be so low that the
inferior border will interfere with
the frenum when the tongue is
raised.
 The position of the clasps and
rests is determined by the rest
seat preparations and by the
ledge created during the blockout
procedure.

23. Spruing
 Spruing for casting of removable
partial dentures involves a large
quantity of metal, so special
attention must be given to points
of attachment, directions of the
sprues, and the direction of flow
of the molten metal.
 There are two basic types of
sprues, single and multiple.
 A heavy sprue is an additional
aid for offsetting this shrinkage.
 It acts as a reservoir for the
casting because its bulk remains
molten longer than the rest of the
casting and supplies molten
metal to those areas which
solidify and shrink first.

24.  Main sprues should always be
attached to bulky sections of the
wax patterns. Never attempt to
feed a thick section through a thin
section to reach a heavy section,
an additional or auxillary sprue
should be used.
 Mandibular partial dentures are
usually sprued through a hole in
the centre or the refractor cast
because it is easier to attach the
sprue leads.
 Maxillary casts are sprued the
same way if the shape of the
castings permits, other wise, they
are sprued from above.

25. IX. INVESTING, BURNOUT &
CASTING
 The investment for RPD consists of
two parts the investment cast and on
which the pattern is formed and the
outer investment surrounding the
cast and pattern. Investment must
conform to the shape of the pattern
and must preserve the configuration
of the pattern as a cavity after the
pattern is eliminated thorough
vaporization.
The burnout has
three purposes :
It drives off moisture
in the mold.
It vaporizes and thus
eliminates the
pattern leaving the
cavity in the mold.
It expands the mold
to compensate for
contraction of metal
on cooling.

26. The method of casting will vary widely with the alloy
and equipment used. All methods use force to
quickly inject the molten metal into the mold cavity.

27. X. FINISHING &
POLISHING THE
FRAMEWORK
 After the framework is obtained by
divesting the sprues are removed
although some authorities prefer that
the sprue not be removed. Care should
be taken while polishing a cast clasp
arm.
 High speeds are preferred compared to
lower speeds. The wheels or points and
the speed of their rotation should do the
cutting. Excessive pressure heats the
work, and slows the cutting.
 A definite sequence for finishing should
be adopted and followed for every
framework. Clean polishing wheels
should be used. Make sure each
finishing operation completely removes
all scratches left by the preceding one.
Each successive finishing step uses a
finer abrasive and therefore cuts more
and slowly requires more time to
accomplish.

28. XI. SELECTING &
ARRANGING TEETH
• The teeth are set in harmony
with the opposing dentition.
XII.
FLASKING,PROCESSI
NG,DEFLASKING &
FINISHING

30. References:
 Textbook of prosthodontics-
Deepak Nallaswamy
Veeraiyan- 2nd edition.
 Textbook of prosthodontics-
V Rangarajan- 2nd edition.