Fluid denture resin processing in a rigid mold

Dental technology DANIEL

Fluid

H. GEHL

denture

Frank F. Koblitz, Hugh E. Wolfe, York, Pa.

and

S. HOWARD

resin

PAYNE,

processing

B.S.,* Richard C.D.T.***

in

A. Smith,

Associate

Editors

a rigid

D.D.S.,**

mold and

M

any fluid resin techniques of denture base processing employ reversible hydrocolloid molds.‘-” This simplifies flasking and deflasking, reduces finishing time, and permits the use of relatively inexpensive equipment. However, problems with these procedures have been reported. 4-14 Among these are: tooth movement and tilting of the cast, vertical dimension decrease, seepage of resin onto the teeth, and dimensional changes in the denture base during processing. Viewpoints vary concerning the seriousness of these discrepancies. Winkler’” has stated, “With further research . . . pour resins could conceivably replace the conventional compression-molding procedure utilizing heat-curing resin.” As one approach to the problems associated with fluid resin processing, a system has been evolved combining elements of conventional investment technique with those of the pour technique. A rigid, modified gypsum investment is used as a replacement for the hydrocolloid investment. The investment is poured into disposable plastic accessories. The purpose of this article is to describe the technique used for processing complete and removable partial denture bases with a fluid resin in this unique rigid mold. The investing material is firm enough to serve as its own “flask” so that no additional metallic container is needed to enclose it. At the same time, the investment is friable enough so that it can be readily removed from the completed denture with a laboratory knife after polymerization of the fluid resin is completed. TECHNIQUE

FOR COMPLETE

DENTURES

1. Remove all excess wax from the surfaces of the teeth, and seal the waxed-up denture to the cast in the usual manner. The cast should taper from the base approximately five degrees occlusally toward the land arca, which should be approximately v~ inch wide. York,

*Section Pa.

Head,

Physical

**Director

of Professional

***Director

of Laboratory

Chemistry, Research, Research,

Central

Research

Dentsply

International,

Dentsply

International,

Laboratory, York, York,

Dentsply

International,

Pa. Pa.

339

340

Fig,

Koblitr,

1. The

Smith,

cast with

and

denture

wax-up

Fig. 2. The of the plastic

sprues base.

for

the maxillary

Fig. hrel

sprues

for

the

3. The area.

J. t’rosthet. September,

Wolfe

has been attached denture

mandibular

extend

denture

are

to the surface so that

they

attached

of the plastic

are even

to the most

with distal

Dent. 1973

base. the inner point

stt I;

4 each

2. Attach the stone cast to the surface of the plastic base with \vas provided in the manufacturer’s kit” (Fig. 1) . 3. Attach soft wax sprues to appropriate areas of the denture wax-up. For :I maxillary denture, there should be three sprues approximately parallel that extend horizontally: one from the most distal portion of each tuberosity area and one from denture, two sprues are needed : the midline of the palate (Fig. 2) . F or a mandibular one at the most distal point of each side of the denture (Fig. 3). These sprues should extend to be approximately even with the inner step of the plastic base. 4. Wrap a plastic strip, provided in thr kit. around the inside rim of the basr. and staple the ends together (Fig. 4). 5. Measure 12 ounces by volume of the investment powder provided and 6 ounces by volume of water. h4ix the powder and liquid in a plaster bowl l\ith 15 to 30 seconds of hand spatulation. Mechanical or vacuum spatulation is preferable of available. 6. Pour the investment into one side of the plastic “flask” while this assemblage is held on a vibrator (Fig. 5) . When the teeth and/or cast have been covered Ilit at least y! inch of investment, continue vibrating for a few seconds to encourage cscap?c of air bubbles. 7. After the investment has set for 15 minutes, remove the staples, plastic strip. and plastic base from the hardened investment (Fig. 6). 8. Trim enough of the inrrstmcnt material awa) front the base of thr (‘ast in ;I “V” groove so that the edges are exposed to a depth of about ‘/ inch (Fig. 7 !. This facilitates removal of the cast from the investment later. 9. Trim investment away from the spruc holes to form funnel-shaped orifices (Fig. 8) If investment has covered the wax sprues, it is still easy to visualize their location by a distincti\re shadowed appearance of the invc’stinent covering them. 10. Cut a flat surface on the area of the investment opposite the sprue with a laboratory knife. This permits the invested denture to stand upright by itself xvith the sprues up (Fig. 9). *TruPour

Fluid

Resin System,

Dentsply

International,

York,

Pa

Fluid

resin processing

in rigid

mold

341

Fig. 4. A plastic strip provided by the manufacturer is wrapped around the inside rim of the plastic base and stapled. Fig. 5. The investment is poured into the plastic “flask” while it is held on a vibrator.

Fig. 6. The staples, plastic strip, and plastic base are removed from the hardened investment. Fig. 7. Investment is trimmed away from the base of the cast in a “V” groove to expose the base edges. 11. Immerse the invested denture in boiling water for eight minutes. 12. Remove it from the water, and gently tease the cast from the investing material (Fig. 10) . 13. Rinse the wax away from both cast and investment with clean boiling water. 14. Brush both with a soft brush and detergent, and follow this with a clear, clean, boiling water rinse. Meticulous attention to neatness and cleanliness is absolutely necessary. 15. Pour about an ounce of the separator provided into a small glass or a paper cup. 16. Brush or flood the separator liberally onto the cast and throughout the den-

342

Koblitz,

Smith,

Fig.

8. Investment

and

is now

Wolfe

trimmed

away

from

Fig. 9. A flat surface cut with a knife on the to stand upright by itself in later procedures. Fig.

10. The

Fig. I!. drIergent, drain.

cast

is teased

The investment treated with

gently

out

the sprue

holes.

side opposite

of the investment

the sprues

permit\

the awmbla~~~

~l~oltl.

mold and the cast have been clcarwd of wax with boilinK water and rinsed, cooled in a water bath. ;11rd placed t;, the separating. agent,

~llolcl. ‘This may bc done as soon as the surlaw lnoisture wrnairlin~ lrom thf> boiling water rinse has drained or cvaporatcd. 17. Hold thr cast and denture mold vertically to allow the ~xccss sep:wator 1~‘ drain, and then rinse gently with cool water (65’ F. j 18. Stand both the in\.rstment and the cast xxartically to drain and dry fat, 12 11Gnutcs. 19. Submerge both the cast and the flask in cool water (65” E‘. b for eight minutes. 20. Ikmovc and stand both vertically to drain until they are free of xvatcr (Fig. 11 ‘1, CZarefully blot any excess crater frown the pins and diatoric arcas of the: porcelain teeth. 21. Snugly reseat the cast in position. Secure it in plncr with rubber bands and a small jar lid or retaining cap (Fig. 12). 22. Stand this assembly on the bench top with thr sprues up. t11rc

Volume Number

30 3

Fluid

Fig. 12. The cast has been reseated a retaining cap and a rubber band. Fig.

13. The

fluid

Fig.

14. The

fluid

Fig.

15. The

investins

Processing

the

denture

resin

resin has filled material

acrylic

into

is carefully the mold is readily

its keyway poured

resin processing

in rigid

in the investment

and is held

into

a side sprue

hole.

from

the processed

mold

343

securely

with

cavity. removed

denture

with

a knife.

resin

1. Mix 28 ml. of denture base powder and 13 ml. of liquid with the receptacles provided, and stir gently for 15 seconds. Permit the mixture to stand an additional 15 seconds to release any entrapped air. 2. Holding the flask assemblage in one hand, tiit it at approximately a 45 degree angle toward yourself, and pour the mixed fluid denture base material down a side sprue until the flask is half full (Fig. 13). 3. Rock the flask gently from side to side to dislodge any air bubbles, and then pour the remainder of the mixture into the same hole until the material fills all sprues. 4. Stand this assemblage on its flattened edge on the bench top for three to five minutes (Fig. 14). 5. Place it in a pressure pot with sufficient water ( 140° F.) present to immerse the flask to within 1 inch of the sprue openings.

344

Koblitz,

Smith,

and

Wolfe

Fig. 16. The acrylic resin sprues are removed from the denturr. Fiz. 17. The dentures have been repositioned on the articulating instrument for occiusal c(ilrcctions. In this instance. the in&al pin trpeninq was O.OOi inch or approximately 0.2 ~IIII. Fig. 18. The drntur?s have brcn rt~no~ed from the cast. trimmed, and polished. Fin. 19. Undercuts have been blocked out with plaster, and the dcntLlrc’ basr arca ha\-c beer! united with auxiliary facial and lingual sprues. The main sprurs in thic in\lancr 31~1 \irniIar IO thrJ\e uscsd for a mandibular c~omple~c denttrrcs. 6. Process the denture for SO minutes at ;I pressure of 20 p.s.i. A thermostatically controlled pressure pot is preferred to maintain constant water temperature. Finishing

of

the

I. Remove the 15 minutes. 2. Remove the 3. Remove the ment (Fig. 16). 4. Position the occlusal corrections

dentures

processed

denture

in its “flask,”

and immerse

it in cool water

investing material with a plaster knife (Fig. 15). acrylic resin sprues from the denture with an appropriate denture in the articulating before the cast is removed

for

instru-

instrument (Fig. 17) for any needed from the inner aspect of the denture.

Fluid

resin processing

in rigid

mold

345

Fig. 20. The mandibular removable partial denture has been remounted on the articulating instrument to occlude with the maxillary complete denture processed for the same patient. The pin opening was approximated as 0.003 inch or 0.1 mm. by a feeler gauge curved into the in&al table. 5. Finish and polish the denture in a routine manner. Little is required than removal of peripheral flash and polishing of these edges (Fig. 18). PROCESSING

A REMOVABLE

PARTIAL

other

DENTURE

Basically the same method is used to process a removable partial denture base as is employed for a complete denture. The main difference is the need for blocking out undercuts. This is readily accomplished with plaster. This step is done in a manner very similar to that normally used during flasking partial dentures for conventional compression molding processing. Time expenditure is minimal. The principles used in spruing a removable partial denture are basically similar to those for complete dentures. The various denture base areas are united by auxiliary facial and/or lingual sprues. These are located so as to encourage the flow of denture resin and the expulsion of air. The main sprues are attached at what will be the highest part of the denture base during the pour procedure. In the instance illustrated (Fig. 19)) the spruing is very similar to that for a complete mandibular denture. The remaining procedures are performed essentially as those for complete dentures. The denture should be remounted for occlusal corrections (Fig. 20) and then finished. SUMMARY A technique has been described for processing denture bases with a fluid resin in a rigid, friable mold. The method requires no specialized equipment such as metal flasks or a hydrocolloid conditioning apparatus. The technique eliminates the timeconsuming step of sorting and replacing artificial teeth in a hydrocolloid mold. AS

346

Koblitr,

Smith,

and

Wolfe

Ivith any denture processing technique, requisite of ;I satisfactory result.

meticulous

attention

to detail

i:, the prilll:i

References 1.

Mirza, F. D.: Dimensional Stability of Acrylic Resin Dentures, J. PROS~F,T. DE&T. 11: 848.857, 1961, 2. Fairchild, J. M.: The Fluid Resin Technique of Denture Base Formation. J. (lalif. Den1 Assoc. 43: 127-138, 1967. :i. Winkler. S.: Pour Technique for Denture Base Prcrcrs\ing, Dent. Dig. 73: ZOO-ZO3. 1967. -1.. Shepard, W. L.: Denture Bases Processed From a Fluid Resin, J. PROSTIIET. DEX~,. 19: ‘161572. 1968. i. Weaver, R. G.. and Ryge, G.: Advancements in Processing Techniques, J. .\la. Der:r .\ssoc. 33: 22-27, 1969. 6. Stanford, J. W., editor: Guide to Dental Materials and Devices, ed. 6, Chicago~ 1971-l 97:; American Dental Association, pp. 98-99. i. Dutton, D. i\., Swoope, C. C., and M&a, J. I’.: A ( :omparison of Vertical Charig+ il: Dentures Processed by Two Methods, Int. Assoc. Dent. Res. .4bst. No. 236, March, 1968. 8. Civjan. S., Gardner, T. V., Worthen, D. F., and de Simon. L. B.: Evaluation of‘ a “Flr~id” Dentrue Base Resin, Int. i\ssoc. Dent. Res. Abst. No. 233, March, 1968. 9. Inge. M’. ,4., Jr., and Taylor, D. F.: Dimensi<~nal Chanqes in Denture~.Procrs\etl ily thv Fluid Resin Techniqur, Int. Assoc. Dent. Res. .\bst. Nrl. 173, March. 1970. 10. Goodkind, R. J., and Schulte, R. C.: Dimrnsic~nal Ac,c,llracy of Pour Acrylic Resin anti Conventional Processing of Cold-Curing Acrylic R&II Ilasec. ,J. I’ROST,FIET. DENT. 24: 662-668, 1970. 11. M’inkler, S., Ortmnn, 11. R., Morris, H. I:.. and l’lczi,l, R. :\.: Prrwes\ing Changes in Complete Dentures Constructed From Pour Resins. ,J Am. Dent. Assoc. 82: ‘149.31,Y 1971. 12. Kraut, R. A.: A Comparison of Denture Base .‘.rcuracy. J. Am. Dent. Assoc. 83: 352-3.ii 1971. 13. Grant, A. A., and Atkinson, H. F.: Comparisorl Bctwcen Dimensional .Yccuracy uf Dentures Produced With Pour-Type Resin and With IIeat-Processed Mawrials. ! PKOSTHET. DENT. 26: 296.301, 1971. 14. Winkler, S.. Morris, H. F., Thongthammachat. S., and Shorr, J. H.: II:\-estina Mediurrl\ for Pour Resins, J. Am. Dent. Assoc. 83: 8.18-85 1, 197 1. I?. Winkler, S.: The Current Status of Pour Resins, ,I. P~osurli,r. DENT. 28: 58()-X+. 19;:;. 500 W. Couxce YORK, PA. 17404

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