Duplication of cd/ dental crown & bridge courses

DUPLICATION OF COMPLETE
DENTURE PROSTHESIS
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.comwww.indiandentalacademy.com

Duplicate complete denture prosthesis
can be defined as-
A second denture intended to be a
replica of the first.
(The Glossary of Prosthodontic Terms.
Seventh Edition. J Prosthet Dent.
Jan1999; 81: 1)

Why and when duplication of complete
denture prosthesis is indicated!
Those patients who may have difficulty
adapting or are unwilling to learn new skills.
Studies have reported that older adults often wear
the same complete dentures for 20 years, even
upto 50 years (Ettinger et al 1984). The degree of
adaptive ability possessed by patients is related
to the health of the supporting tissues, their
neuromuscular co-ordination and their motivation
to learn new skills.

A patient may be wearing a prosthesis that is
inadequate but it is comfortable and efficient,
and they are able to control it with muscular
skills developed over a long period. However
a new prosthesis requires the development
of a new learning sequence and the will to
persist in learning it.
 Those patients with the greatest risk
are frail older adults whose ability to
adapt to new dentures may be
impaired, because they are physically
frail or suffering from diseases such as
Parkinson's or dementia.

 Those complete denture wearers who are
apprehensive about the possibility that their
dentures might be broken or lost. They also
have grave misgivings about being without
them during required relining or repair.
The duplicate denture can serve as an
impression tray, temporary denture, an
initial replacement in the fabrication of a
new denture, a surgical guide, a
radiographic and surgical stent during
fixture placement in implant therapy, or it
can be used for research purposes.www.indiandentalacademy.comwww.indiandentalacademy.com

Contra indication:
Include any serious defects of the dentures
prosthesis. Hence, a careful evaluation of the
supporting hard and soft tissues and the prosthesis
is must prior to making the decision for duplication
procedures.
The denture should be examined and evaluated for:
Existing or repaired fractures, craze lines, and
missing or replaced teeth.
Esthetics, phonetics
Accuracy of fit
 Vertical and centric relation

If necessitated make a final
impression with a thin layer of
zinc oxide eugenol in the original
denture in centric occlusion to
increase retention and reduce
possible changes in vertical
dimension of occlusion in the
duplicate denture.
Perform muscle trimming, and
remove excess impression
material extra orally from the
borders. www.indiandentalacademy.comwww.indiandentalacademy.com

Techniques of denture duplication
I. Denture duplication using
autopolymerizing acrylic resin.
1. Modified flask method (Brewer &
Morrow 1975, Nassif 1984)
2. Modified flask method using silicone
impression material
(Manoli
1969)
3. Pour resin flask method (Boos and
Carpenter 1974)
4. Cup flask method (Wagner 1970, Singer
1975)
5. Two tray method (Cooper and
Watkinson1976, Lindquist 1997)www.indiandentalacademy.comwww.indiandentalacademy.com

II. Denture duplication using heat activated
acrylic resin.
1. Flask method (Azarmehr P & Azarmehr
HY 1970)
2. Sectional mold technique (Mohamed TJ
and Faraj SA 2001)
3. A technique by Izharul Haque Ansari (1994)
4. A technique by Lindquist TJ and Ettinger RL (1999)
5. Duplication procedure for complete dentures by
CAD/CAM (Kawahata N et al 1997)

I. Denture duplication using autopolymerizing
acrylic resin.
1. Modified flask method (Brewer & Morrow 1975,
Nassif 1984)
Procedure:
1. Modify the denture flask by removing a
rectangular section from the upper part (Fig
1.1). This opening will allow access for the
sprues. Although it is unnecessary to have a
new flask, the parts should fit together
accurately without rocking.

2. If the denture to be duplicated has thin areas,
add wax to the exterior surface of the denture to
thicken these areas before flasking (Fig 1.2).
Fig. 1.1
Fig. 1.2

3. Roll utility wax to form a sprue approximately 75 mm
long and 15 mm in diameter (Fig 1.3).
4. Attach the sprues to the lingual surface of the heels
of mandibular dentures and to the palatal surface of the
tuberosity region of maxillary dentures (Fig 1.4).
Fig. 1.3 Fig. 1.4

5. Paint the round plate from the lower part of the flask with
an adhesive, and insert it from the exterior surface, rather
than from the interior (Fig 1.5). This insertion prevents
distortion of the alginate mold by inadvertent displacement of
the plate while handling the flask.
6. Apply the same adhesive to the interior surface of the flask
to facilitate retention of the alginate (Fig. 1.6).
Fig. 1.5 Fig. 1.6

7. Mix eight scoops of regular setting alginate with the
recommended volume of water for the first pour. Cooling the
water will allow additional working time.
8. Mix the alginate with a mechanical spatulator under
reduced atmospheric pressure to minimize air
inclusions in the material. Hand spatulate thoroughly if
a power mixer is unavailable.
Fig. 1.7
9. After mixing, place alginate
into the interior of the denture
with a finger or a brush, taking
care to avoid the entrapment of
air and resultant voids. Fill the
denture completely (Fig. 1.7).

10. Place the remainder of the alginate mix in the lower part of
the flask.
11. Settle the filled denture into the mix, as during a
routine flasking procedure. The wax sprues can support
the denture, thereby preventing it from sinking into the
alginate. The alginate should extend approximately 3 mm
onto the exterior surface of the denture (Fig. 1.8).
12. After the alginate has set, trim away any excess that flows
over the edges of the flask.
13. Place the upper part of the flask in position, and adapt
the wax sprues to seal the rectangular opening (Fig. 1.9).
Fig. 1.8 Fig. 1.9

14. Mix six scoops of alginate with three times the
recommended volume of water to make a pourable
consistency
15. Pour the alginate into the flask slowly. Use a finger or
brush to wipe alginate onto the teeth of the denture to
minimize voids. The second pour will not stick to the first
one.
16. Completely fill the flask, and place the top in position.
Allow the alginate to set approximately 15 minutes or longer
if using cold water (Fig. 1.10).
Fig. 1.10

17. After the alginate has set, open the flask, and remove
the denture and sprues.
18. Place the lower part of the flask, that is, the cast side,
in a humidor or under a wet towel.
19. Dry the tooth indentations in the alginate carefully.
Use
a gentle stream of air or a strip of cleansing tissue to
remove water from the tooth imprints (Fig. 1.11).
Fig. 1.11 Fig. 1.12

19. Add autopolymerizing tooth-colored resin of the proper
shade to the tooth indentations by the sprinkle-on or paint-
on.
20. Carefully add the tooth-colored resin in increments, and fill
the indentations to the cervical line (Fig. 1.12). Exercise care to
improve materially the resultant duplicate denture. It is possible
to add incisal, body, and gingival shading, but it requires
considerable skill to achieve good results.
21. Allow the tooth-shade resin to set for a few minutes
before assembling the flask.
22. Carefully dry the alginate in the lower flask; then
assemble the flask halves, and clamp or secure them with
rubber bands.
23. Mix a pour-type resin according to the manufacturer's
recommendations, and pour it into one sprue.
24. Rock flask gently while pouring to minimize the entrapment
of the air. www.indiandentalacademy.comwww.indiandentalacademy.com

25. Fill one sprue until the resin fills the other sprue, thereby
indicating that the mold is full (Fig. 1.13).
26. Attach modeling clay to the filled flask, place it sprues
upward in warm water in a pressure container, and cure the
denture at 20 psi for 30 minutes (Fig. 1.14).
Fig. 1.13 Fig. 1.14

27. Remove the cured denture, and examine it for nodules and
voids (Fig. 1.15).
28. Cut off the sprues, and finish and polish the denture
(Fig. 1.16).
Fig. 1.15 Fig. 1.16

Problem areas
 The principal problems associated with this method
are, the inability to obtain a bubble-free void less mold
 Failure to achieve an accurate duplication of
denture teeth without rounded incisal angles.
Difficulty in producing an accurate alginate mold
and resultant duplicate denture.

Solution of problems:
Mixing the alginate in a mechanical spatulator under
reduced atmospheric pressure helps to minimize voids.
Painting the alginate into the denture with a finger or brush
also results in fewer voids.
 Making acceptable autopolymerizing resin teeth in the
denture requires skill and practice.
Make certain that the tooth indentations in the alginate are
dry to minimize the possibility of rounded incisal angles in
the resin teeth (Fig. 1.17).
Add the resin in increments, and tilt the flask while
pouring
Fig. 1.17

It appears, at least clinically, that the
duplicate denture made by the alginate mold-
pour resin system does not exhibit the same
adaptation to the tissues as the original
denture. Therefore the duplicate may require
more adjustment by the dentist. It is best to
consider this duplicate denture a spare one for
emergency use only.

A modification in the above technique was given by Nassif J
and Jumbelic R in 1984. The change was in the fabrication of
the teeth.
Procedure:
1. Select a shade that harmonizes with the existing teeth (Fig.
1.18).
2.Make an irreversible hydrocolloid impression of the denture
in a stock tray. The impression need only include the artificial
teeth (Fig. 1.19).
Fig. 1.18 Fig. 1.19

3. Duplicate the teeth by means of a custom-blended polymer
with monomer in a sprinkle-on technique (Fig. 1.20).
4. Place the impression tray slightly overfilled with tooth-
colored resin in a pressure pot that contains 110° F water,
and process at 20 to 30 pounds of air pressure for 15 minutes
(Fig. 1.21).
5. Remove the acrylic resin teeth from the impression mold
and carefully trim the excess interproximal resin (Fig. 1.22).
Fig. 1.20
Fig. 1.21
Fig. 1.22 Fig. 1.23

6. Seat the teeth in the mold and apply light coat of monomer to
the resin to prepare it for chemical bonding with the denture
base resin (Fig. 1.23).
Fig. 1.25
Fig. 1.24

The basic technique in all other methods is
same to produce mould for pouring the
duplicating auotpolymerizing resin material.
Difference was.
 material used for producing mould such as
polyvenyl siloxane(putty) material was used
instead of modified flaks stock metal
impression trays and plaster moulld and
porcelain cup were used.

II. Denture duplication using heat
polymerized acrylic resin.
The material used for duplication of the
prosthesis is heat cure polymerized acrylic
resin due to many of its added advantages
over auto polymerizing resin. The basic
principles is same in the methods. The
Sectional mold technique by Mohamed TJ
and Faraj SA 2001 is discussed here.
A sectional mold and dental stone are used
to invest the denture, and heat-activated
acrylic resin is used to duplicate both the
denture teeth and base.www.indiandentalacademy.comwww.indiandentalacademy.com

Procedure:
1. Make a final impression with a thin layer of zinc oxide
eugenol in the original denture in centric occlusion to
increase retention and reduce possible changes in vertical
dimension of occlusion in the duplicate denture. Perform
muscle trimming, and remove excess impression material
extraorally from the borders.
2. Create a master cast by pouring the impression with
stone. Apply a thin layer of petroleum jelly to the outer
surface of the denture. Remove any excess jelly with a
clean piece of cotton.
3. Flask the master cast and original denture in the lower
half of a Broden flask (Svensaka, Sweden) by using dental
stone as the investing material.

4. Use a brush to paint the outer surface of the denture with the
stone mixture. Use the remaining stone to invest the denture until
only the tips of the teeth remain.
5. Apply cold mold seal separating medium on the stone surface,
and pour a third layer of stone (the cap stone) to complete the
flasking.
6. Complete the deflasking after immersing the flask in warm
water at 70°C for 15 minutes for easier removal of the denture
from the cast. Softening of the impression material may prevent
potential fracture of the cast. If fracture does occur and the
fracture line is clean, it can be easily fixed with the appropriate
adhesive material (Fig. 7.1).

Fig. 7.1.
Deflasking.
Fig. 7.2. Denture with investing
stone separated from upper half
of flask.
7. Remove the cover of the upper half of the flask, loosen the
lateral screw, and remove the stone with the denture from the
upper half of the flask (Fig. 7.2).
8. Separate the cap stone layer from the second layer by using a
plaster knife.
9. Make 3 cuts with a minisaw in the heals and at the midline on
the second layer of stone (Fig. 7.3).www.indiandentalacademy.comwww.indiandentalacademy.com

10. With a plaster knife, separate the second layer from the
denture. Clean the denture, and return it to the patient (Fig. 7.4).
Fig. 7.3. Cap stone layer
separated from second layer.
Fig. 7.4. Parts of second layer with
original denture after separation.

11. Gently reassemble the 4 stone pieces to their original positions
in the upper half of the flask. To get the exact position of the parts,
position the upper half with the lower half of the flask under the
press, and then tighten the lateral screw (Fig. 7.5).
12. Separate the flask, and immerse the upper half in warm water
for 5 minutes. Melt hard modeling wax in a container, and then
pour the molten wax into the teeth mold (Fig. 7.6).
Fig. 7.5. Stone
pieces
reassembled in
flask.
Fig. 7.6. Molten wax
poured into teeth mold.

13. After gradual cooling, immerse the upper half of the
flask in cold water (25°C) for 15 minutes. Remove the cover
of the upper half of the flask, and loosen the lateral screw of
the flask. Remove the stone and wax from the flask gently.
With a plaster knife, separate the cap stone layer from the
second layer. Then separate the parts of the second layer to
get the arch wax of the teeth intact (Fig. 7.7).
Fig. 7.7 Arch wax of teeth separated
from stone pieces of upper half.

14. Flask the arch wax in another flask. Then process the arch
wax in Crown and Bridge tooth-colored heat-activated acrylic.
Finish the arch teeth gingivally and interdentally after deflasking.
15. Place the acrylic arch teeth in position on the cap stone with
the other 3 pieces of the second layer, and place the upper half of
the flask on it. Press the lower half of the flask, and tighten the
lateral screw. Finally, separate the flask halves (Fig. 7.8).
Fig. 7.8. Acrylic arch teeth in
mold before packing.

16. Apply cold mold seal separating medium on stone surface,
and pack and cure pink heat-activated denture base material.
Finish and polish the duplicate denture.
The only disadvantage of this technique is the risk of
fracture of the master cast when undercuts are present. Given
this risk, the technique is preferable for situations in which
there are no undercuts. But if fracture does occur, repeating
the entire technique is recommended.

Summary
Patients may have difficulty adapting to a new
prosthesis for either physical or psychological reasons.
Duplication of patient’s old denture by different methods
using autopolymerizing and heat polymerizing acrylic resins
have been discussed. The duplicate dentures fabricated using
autopolymerizing acrylic resin can be used for short period of
time. The duplicate denture fabrication techniques using heat
polymerizing acrylic resins minimize the changes to the new
denture, making it easier for the patient to adapt to new
dentures.

Duplication of cd/ dental crown & bridge courses

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