Al Azhar university Removable Prosthodontics Lama El Banna Dr. Waseem Moshtaha

1. Waxing up
Dr. Waseem Bahjat Mushtaha
Specialized in prosthodontics

2. Waxing-up is the contouring of the trial
denture base into the desired form to
produce a denture base that reproduces the
contour of the original tissues in the
dentulous mouth in order to:
1-procedure a pleasing natural appearance
2-aid in retention and stability of the dentures
as the tongue, cheeks and lips will lie
properly against the denture base and help
in seating the dentures.

3. Waxing may be accomplished either by
placing a piece of soften base plate wax to
the base and gradually carving it down to
the desired form or by deposing molten wax
in the proper area to build up the desired
form so that:
1-the anterior portion of the maxillary denture
base should be shaped so that together with
the teeth, it provides a pleasing form for the
lip, and procedures a slight overall convex
effect.

4. 2-the contour of the mandibular denture in the
anterior region is relatively straight.
3-the form of buccal flange from the premolar
backward should face downward and
outward for the upper and upward and
outward for the lower. This contour allows
the buccinator muscle to lie against the
denture and aids in its retention and stability

5. 4-the contour of the lingual surface in the anterior
region should be straight and slope to the lingual
border. The contour of the lingual surface in the
premolar and molar region is relatively straight, as
a concave surface in this area provides space for
the tongue to catch and lift the denture
unintentionally during movement. The lingual
surface posterior to the second molar(the
retromylohyoid region) faces downward and
inward and is thinned so that it does not interfere
with normal tongue movement

7. 5-any excess wax around the teeth is
removed. The remaining wax is carved at
the cervical line of artificial teeth to
simulate the natural appearance of the
gingival margin and gingival papillae. The
gingival papilla of the denture should be
convex both occlusogingivally and
mesiodistally, and should fill the
interproximal space below the contact point.
Carving the gingival margin should be
carried out with a knife held at an angle 45
to the cervical.

8. 6-the region of attached gingival may be stippled to
produce a finished denture whose surface show an
a "orange-peel effect". This may be produced with
tooth brush; placed on lightly flamed wax surface
on the wax. The bristles produce many small
indentations in the wax.
7-the wax above the roots should be contoured to
simulate the root prominences present in dentulous
mouths. The root prominences should fade out
before the borders are reached. the root
prominences of canines are the most definite
prominences in the dental arch.

9. 8-the palatal surface of the maxillary trial
denture base should be waxed to a nearly
uniform thickness of 2.5 mm. wax is
further added and carved
9-the wax at the borders is contoured as in the
impression to produce a perfect peripheral
seal.
10-finally,wax solvent is used to remove any
wax film from the surface of the teeth
otherwise, denture base material will adhere
to the teeth making finishing procedures
difficult.

10. Denture processing
1-Flasking
2-Wax elimination
3-Packing and curing

11. 1-Flasking
Dental flask: is an instrument into which the
contoured, waxed-up denture base is
covered into resin, to make a denture. This
done by investing the wax denture,
eliminating the wax to form a mould into
which methyl-methacrylate resin is packed.

12. Component parts of the dental flask
1-the base of the flask, is in the form of a cup. It
contains a round knock-out plate. For the lower
denture, the edge of the base is higher posteriorly
to accommodate the posterior upward inclination
of the mandible.
2-The middle part of the flask is in the form of a
ring, it fits accurately into the base through pins.
3-The top parts of the flask “the lid” which fits
accurately into the ring and contains escape holes.

15. Flasking the denture is done in three steps. In
the first step, the cast is secured into the
base of the flask with stone. Taking care
that no undercuts exist on the surface of this
first step. In the second step, the ring of the
flask is put in place, and stone is poured up
to the occlusal surface of the teeth.
The final third step is accomplished when the
top portion of the flask is poured and the lid
is placed on the flask. The third stage is
referred to as capping

16. Procedure for flasking the denture
1-Seal the waxed denture base to the cast
using base plate wax.
2-Remove the waxed up denture from the
articulator.
3-Place the dentures and casts in the flask to
check the height of denture teeth in the flask
To ensure that the flask and the casts are of
compatible size.

17. 4-The waxed up dentures placed on their
casts are soaked in water at room
temperature for about 5 minutes. Hence the
casts are thoroughly wet removing less
water from the investing stone mix.
5-Paint the casts with plaster separating
medium to facilitate deflasking, and the
inside surface of the flask is lightly coated
with vaseline.

18. 6-Mix artificial stone and place it in the base
part of the flask. Settle the waxed denture
and the cast into the mix, and center the cast
in the flask. The posterior portion of the
cast should at the same level with the edge
of the flask, and the occlusal plane
approximately parallel to the base of the
flask.
7-Smooth the stone around the cast and block
any undercuts that would prevent separation
of the flask halves, such undercuts occur
commonly in the posterior lingual region of
mandibular dentures.

19. 8-Place the ring of the flask in position on
the base part to ensure that no stone remains
on the rim preventing complete seating and
that teeth do not protrude above the top of
the flask. After the stone has set, paint
plaster separating medium on the first stage
stone. Take care not to place separating
medium on the waxed denture or teeth.

20. 9-A mix of artificial stone is poured into the
flask while the ring is in its position, place
the flask on a vibrator to ensure that the
stone reaches all cervices around the teeth.
10-Remove the stone with finger to expose
the occlusal surface of the teeth.
11-The stone is allowed to set, then a plaster
separating medium is painted on the surface
of the second stage.

21. 12-A mix of stone is poured so that the flask
is over-filled to produce the third stage
stone.
13-Place the lid on the flask firmly and tap it
gently to ensure that the flask has been
completely filled.
14-Allow the stone to set before the wax is
eliminated.

32. 2-Wax elimination
Now, after the dentures have been flasked, the
wax must be eliminated to form a mould
into which the resin may be packed. This is
done by placing the flask in hot water
which softens the wax. The flask is then
opened and the wax. The flask is then
opened and the wax is flushed out.

33. Procedure for wax
1-The flask, in the holder, is placed in boiling water
for approximately 5 minutes, then removed.
2-with the blunt end of a plaster knife, separate the
flask. It is placed in the slot in the posterior
portion of the flask, which is then gently opened.
Discard the softened wax, and plastic denture
base. Then check that no denture teeth have been
dislodged on opening the flask.

34. 3-Clean boiling water, to which detergent has
been added is flowed over the surface of the
teeth, cast, and stone to eliminate all traces
of wax.
4-With a brush, and soap or detergent
solution thoroughly scrub the mould to
reach into all mould recesses. This is
followed with a clean boiling water flush, to
remove any trace of the detergent.
5-Place the flask aside to cool.

42. Painting the tin-foil substitute
Tin-foil substitute or (sodium alginate) is
applied to all stone surface of the cast, and
the flasking stone after the flasks have
cooled to prevent the resin from adhering to
the stone. Pour enough tin-foil substituent
into a small container for use, never dip the
brush into the main container because it is
very easily contaminated, and its
effectiveness is destroyed.

43. A large brush may be used to paint the casts
and the flasking stone while a small brush is
used to carry tin foil substitute around the
teeth. A void covering the teeth otherwise, a
small void will be present around the teeth
in the complete denture. The void will stain
in the mouth and result in a black line
around the teeth.
After the stone in the flask has been painted,
place it aside and allow it to dry. Now the
mould is ready for packing the denture resin

45. 3-packing the denture
1-proportion the monomer and polymer
following the manufacturer’s instruction.
Placed the monomer in a clean mixing jar
and then sprinkle the polymer into it to
ensure that each particle of the polymer is
wet with the monomer. The mixture is then
spatulated with a stainless steel spatula.

46. 2-Cover the mixing jar to prevent evaporation of the
monomer, resulting in a grainy mix. Place the jar
aside until the resin reaches the proper stage
(dough) for packing.
3-Remove the resin from the jar, form it in a roll
and adapt it to the mould in the flask.
4-Place a piece of wet cellophane over the resin.
Placed the flask halves in their position and close
it. This allows the flask to be re-opened for
inspection, adding or removing resin without
adherence of the cast to the tissue surface of the
uncured resin.

47. 5-Place the assembled flask in a bench press slowly.
This permits the flow of acrylic resin into minute
areas of the mold.
6-Open the flask and cut away excess resin
extending around the edges of the flask, so that no
resin is beyond the border of the denture.
7-Trial packing is repeated until no more excess
resin is apparent on opening the flask, all the fine
details are present on the surface of the resin
representing an exact negative replica of the cast,
and until the resin shows a dense shiny surface.

48. 8-Repaint the cast portion of the flask with
tin-foil substitute and allow it to dry.
9-Assemble the flask and close it until metal
to metal contact between the flask rims is
achieved.
10-Place the flask in a processing clamp and
turn the hexagonal handle to close the
clamp tightly.

58. 4-Curing the denture
Denture resins are cured by one of two methods. The
preferred method is curing the resin for 9 hours at
165F (70C). The second method requires curing
the resin at 165F for one hour followed by boiling
for half an hour. After curing, the flasks are
removed from the water and allowed to bench cool
before they are removed from the clamp. The
denture is then ready for deflasking, finishing and
polishing.

59. 5-Deflasking
1-Remove the lid of the flask using plaster knife.
2-The flask is then placed in a flask ejector to
separate the flask from the stone enclosed denture.
3-an alternate method for removing the flask is by
using a hammer to strike the knock-out plate on
the bottom of the flask. The base part of the flask
is removed followed by the top part.

60. 4-Place a knife blade at the junction between
the stone cap and the rest of the stone
enclosing the denture to separate the stone
cap and expose the cusp tip and incisal
edges of the denture teeth.
5-Using a saw, make three saw cut in the
investing stone, one opposite the central
incisor teeth and one at each distobuccal
corner of the flasked denture.

61. 6-Separate the stone sections gently, then
remove stone from the palate or tongue area
using a knife. Don’t remove the dentures
from the casts, special care must be taken to
ensure that the casts are not broken.
7-use a tooth brush to clean out the index
grooves on the base of the cast, to faciliate
accurate repositioning of the casts on the
mounting stone for the correction of any
processing errors.

66. Common errors in the final denture
Problem:
Cured denture has porosity
Cause:
1(Flask unpacked with resin
2(Denture base heated too rapidly
Solution:
1(Fill the mould completely before curing.
2(Bench cure, followed by long curing cycle.

67. Problem:
Cured denture has processing errors
Cause:
1(Denture resin packed at late or rubbery
stage.
2(Flask not properly closed prior to curing
Solution:
1(Pack resin during dough stage.
2(Make certain that metal to metal contact of
flask rim is achieved.

68. Problem:
Stone adhering to surface of denture
Cause:
1(Failure to place tin-foil substitute on stone prior to
packing.
2(Tin-foil substitute contamination with stone
3(Wax elimination not completed during boiling
out, rendering tin-foil ineffective.
Solution:
1(Paint tin-foil properly on stone prior to packing.
2(Use fresh tin-foil poured into a small container.
3(Clean in mold surface and cast surface thoroughly
with boiling water.

69. Problem:
Denture has many acrylic resin nodules.
Cause:
1(Investing stone not properly spatulated.
2(Presence of air bubbles in the investing
stone.
Solution:
1(Mix stone properly.
2(Elimination air bubbles by placing the
flask on a vibrator.