Dental Stone Microwavable Flask How To

بنام خدا

بنام خدا

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Copyright: © 2011 Dhaded S, et al. This is an open-access article distri-

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doi:10.5436/j.dehy.2011.2.00043

Innovative Method for Fabrication of

Microwavable Denture Flasks

Sunil Dhaded a , Rajesh Prajapat a , Neha Dhaded b

a Department of Prosthdontics, A.M.E’S

Dental College and Hospital, Raichur,

India. b K.L.E’S V.K. Institute of Dental

Science’s and research centre, KLE Uni-

versity, Belgaum, India.

Correspondence to:

Sunil Dhaded

Department of Prosthdontics, A.M.E’S

Dental College and Hospital, Raichur,

India.

Tel: +98-44101555

[email protected]

Received: March 10, 2011

Accepted: September 1, 2011

Published: September 5, 2011

Abstract

Introduction: Microwavable denture flasks for polymerization of

acrylic resin are commercially available. However they are expen-sive and smaller in size, large maxillofacial prosthesis cannot be fa-bricated in them. The objective of this report is to showcase a simple technique for the fabrication of microwavable denture flasks which is economical and larger in size.

Clinical innovation: A method of making dental stone flask pattern and a latex rubber mold was used to produce microwavable denture flasks. These flasks are made from the fiberglass liquid resin that is strengthened by the addition of chopped fiberglass strands.

Discussion: Microwavable denture flasks can be made that will be

simple, economical and large enough to accommodate the maxil-lofacial prosthesis. These flasks are strong enough for compression molding and allow successful microwave polymerization of acrylic resin denture bases.

Key words: Fiberglass liquid resin; Fiberglass strands; Microwava-

ble denture flask; Liquid latex rubber.

Clinical Innovation

Dhaded S, et al Fabrication of microwavable denture flasks

http://www.dentalhypotheses.com Vol 2, No 3, 2011 179

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Introduction

Due to the rapid development in dental

material sciences, acrylic resin can also be

polymerized by microwave irradiation, as

first reported by Nishii [1] in 1968. There

are substantial advantages of using mi-

crowave energy for curing of acrylic resin

rather than the conventional water bath

method. These advantages are greatly re-

duced curing time, less cumbersome

equipment, a cleaner method of

processing and better adaptation to the

cast [2]. The conventional metal (brass)

flask cannot be used for microwave

processing as microwave radiation cannot

pass through the metal, instead, a fiber-

reinforced plastic denture flask system

(US Shizai Corp, Santa Monica, Calif) was

developed and became commercially

available in 1985 [3]. Unfortunately, the

most disadvantages of microwave tech-

nique were related to fiber reinforced

flasks as these flasks are relatively expen-

sive, small and have a tendency to break

down after processing several dentures

[4]. Procedure for making oversized mi-

crowavable denture flask using metal

template was also described Mc Kinstry

[3]. Nevertheless, this article describes a

simple method for making microwavable

denture flasks that are capable of holding

large maxillofacial prosthesis, using

commonly available denture flasks hence

eliminating the use of metal template and

also making the procedure economical.

Clinical innovation

The following materials are used to make

a microwavable denture flask:

Middle section of conventional Brass

flask (Jabbar & Co. India).

Bowl and spatula.

Dental stone (Kalstone, Kalabhai Dental

P Limited, India).

Petroleum jelly (Medisoft Pvt. Ltd. In-

dia).

Clean tile.

Lead pencil.

Three 60 ml plastic syringes (Dispo

Van, Hindustan Syringe & Medical De-

vice Ltd]

Three 3/8 inch Metal bolts that are 4

inches long as well as six washers and

three nut to fit.

Liquid latex rubber (DCMM solution,

Devi and CO. Banaglore, India).

A Paint brush 11/2 inches wide.

Chopped Fiberglass Fibers (Naptha Re-

sins, Peneya, Banaglore, India).

Fabrication of microwavable denture flasks Dhaded S, et al

180 Vol 2, No 3, 2011 http://www.dentalhypotheses.com

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Fiberglass liquid resin and catalyst

(Naptha Resins, Peneya, Bangalore, In-

dia). Fiberglass liquid resin is commer-

cially available for use in auto body re-

pair shops.

Power drill (Available at Carpenter or

Hardware Shops).

Three pieces of window or plate glass

approximately 8 inches square.

Procedure for making dental stone

flask

Dental stone flasks were made using mid

section of conventional brass flask. Apply

petroleum jelly to the midsection, make a

thick mix of dental stone and apply on the

outer surface (Appendix 1). After it sets,

remove the brass flask by gently tapping

and trim the excess material. Follow the

same procedure as mentioned above to

make the lower section. Then place it on

unset stone base made using thick mix of

dental stone and seal it from border.

Scoop out stone of approximately two

inch diameter from base, after final set of

the stone, trim the excess. To make the lid,

an outline of the narrower end of midsec-

tion of stone flask was marked on a ce-

ramic tile; thick mix of stone was poured

on the tile. The surface was flattened and

left to set. Later it was trimmed till the

borders touched the outline on the tile.

Soak all parts of stone flask in saturated

solution of calcium sulphate to prevent

expansion of stone [5].

Procedure to create bolt guide

Take a 60 ml syringe (without the piston)

cut the nozzle end of the syringe so that

both the ends are open. Standardize the

position and dimension for the screw hole,

by placing the syringe along the sides of

the flask model. Cut the syringe into 3

parts according to the height of the three

part of the flask model. Apply petroleum

jelly on the inner surface, align the three

parts of syringe, make a thick mix of stone

and pour into the syringe. Similarly make

two more sets of bolt guides for the other

two sections. After the stone has hardened

separate the plastic syringe. Trim on one

side to create a flat surface so as to attach

it to the flask model. Align all the stone

guides in their respective places. Leave 4

mm of space between two bolt guides.

Make a mixture of stone and place in be-

tween the bolt guide and flask model.

Shape the stone to make a smooth transi-

tion between the guide and the flask mod-

el. After stone sets separate all the parts of

the stone flasks and with a sharp knife

complete the shaping to form a smooth

surface (Appendix 2).



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Making of the molds

Latex rubber is recommended for making

the molds because of its ease of applica-

tion and low cost. Place all the parts of the

stone flask on a smooth, flat surface. Place

the two flask models with the inside up.

Do not use any separating media on the

flask models. Paint latex rubber over each

flask models. Let the first coat dry before

applying the second coat. Apply 7-8 coats

(Appendix 3). After the last coat of latex

rubber sets, make a mixture of dental plas-

ter and cover the latex rubber to a depth

of about 10 mm to serve as a backing for

the mold. After the gypsum sets, carefully

separate the stone flask patterns from the

latex to obtain the mold (Appendix 4).

Making of Fiberglass Flask

Mix the fiberglass liquid resin with the

appropriate catalyst, and fiberglass fibers,

to create thick slurry. With this fiberglass

mixture, fill each of the three molds (Ap-

pendix 5) and cover each with a piece of

glass plate. Allow 3 hours for the resin to

harden and remove the gypsum backings

from the latex molds. Remove the latex

mold from fiberglass flask sections. Drill a

hole of 3mm diameter in the middle of the

bolt guide for the insertion of bolts using a

power drill and complete the finishing of

flasks. Even lubricated suction tips can be

used while making the bolt guide to create

the screw holes for insertion of bolts [3].

Drill two holes through the top of the

flask. Assemble all three parts of the fiber-

glass flask, insert the metal bolts. The flask

is now ready for use (Appendix 6).

Discussion

This fibreglass flask can be made of any

size even large enough to accommodate

the processing of most large maxillofacial

prosthesis. Fiber-reinforced plastic was

used in making of these flasks, which act

as a filler and allows it to accept the stre-

nuous pressure when packing a denture

along with the heat associated while mi-

crowave curing. Various sizes of fibreglass

flask can be made with this technique. Dif-

ferent sizes of flasks can also be made us-

ing metal template as described by Mc

Kinstry [3]. One of the major advantages

of using this technique for making micro-

wavable flasks is the cost. Flasks made by

this technique are 10- 15 times cheaper

than the commercially available micro-

wavable flasks.

Kimura [2] advocated the use of poly-

carbon bolts to avoid reflection of micro-

waves during processing. However poly-

carbon bolts expand during processing

and they can break also. There is no de-

trimental effect from the use of metal bolts



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Table1. Few of the key features that differentiate the commercially available microwavable

dentures versus the custom made microwavable dentures.

Commercially Available Microwavable

Dentures

Custom Made Microwavable Dentures

Can be used for only few denture processing. Can be used for many denture processing

Costly Economical, it is around 10-15 times cheaper

than the commercially available one.

Fiber- reinforced plastic denture flask system

(US Shizai Corp, Santa Monica, Calif)

Custom made

Curing large maxillo-facial prosthesis is difficult

or not possible

Curing large maxillo-facial prosthesis is possi-

ble

in microwave processing, and metal bolts

do not expand. This was also reported by

Mc Kinstry [3] and De Clerck [6]. Fiber-

glass, like all common forms of glass, is a

chemically inert substance. However, ex-

posure to these products may cause skin

and eye irritation and the inhalation of fi-

bers may irritate the upper respiratory

tract in few people. As the solvents, com-

pounds and resins used in making of fi-

berglass reinforced flask are mostly flam-

mable; precautions should be taken dur-

ing their mixing, use and storage.

Conclusion

This article describes a simple and eco-

nomical procedure for making oversized

microwavable flasks with the help of ma-

terials, which are easily available. These

flasks are strong enough to withstand

compression molding packing pressure

along with the heat associated with mi-

crowave curing (Table 1).

List of abbreviations

There is no abbreviation.



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Conflicts of interests

The authors declare that they have no

competing interest.

Acknowledgments

This study was not financially supported

by any institution and commercial

sources.

Authors' contributions

Main idea: by SD, RP.

Literature search: by SD.

Data interpretation: by SD, ND.

Manuscript preparation: by RP, ND.

Data collection: by SD, RP.

Funds Collection: N/A.

References

1. Nishii M. Curing of denture base resin

with microwave irradiation with particular

reference to heat-curing resins. J Osaka

Dent Univ 1968; 2: 23-40.

2. Kimura H. Application of microwave for

dental technique. Part I Dough- forming

and curing of acrylics. J Osaka Univ Dent

Sch 1983; 23: 43-9.

3. Mc kinstry RE. How to make microwava-

ble denture flasks. J Prosthet Dent 1990;

63: 104-10.

4. Levin B, Sanders JL, Reitz P. The use of

microwave energy for processing acrylic

resins. J Prosthet Dent 1989; 61: 381-3.

5. Neiman R. Gypsum products. In: Anusa-

vice KJ, editors: Phillips science of dental

materials, 10th edition. Harcourt Asia:

Saunders, 2000; 185-209.

6. De clerck JP. Microwave polymerization

of acrylic resins used in dental prosthesis. J

Prosthet Dent 1987; 57: 650-8.

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Citation : Dhaded S, Prajapat R, Dhaded N. Innovative method for fabrication of microwavable denture flasks. Dent Hypo-theses 2011; 2: 178-189. doi: 10.5436 /j.dehy.

2011. 2.00043

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Appendix 1. Thick mix of dental stone applied on the outer surface of brass flask.



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Appendix 2. Parts of the flask separated.



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Appendix 3. Latex rubber painted over the stone flask to make mold.



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Appendix 4. Mold of lower part of flask after dental stone flask has been separated.



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Appendix 5. Fiberglass mixture is filled in the mold of lower part.



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Appendix 6. Microwavable Fiberglass flask with metal bolts.

Dental Stone Microwavable Flask How To

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