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656 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 83 NUMBER 6

A lthough plastic and reconstructive surgical tech-niques have improved, there still remain patients in

whom prosthetic replacement is advisable for congeni-tal or acquired facial defects of the head and neck. For

these patients, a prosthesis may produce an excellentcosmetic result. Yet, problems of inadequate retentionand orientation of the prosthesis to the defect may frus-trate the patient.1 These problem can be a major con-cern when handling a small facial prosthesis. Advanceshave been made in prosthesis retention through theselective use of soft tissue undercuts, magnets, attach-ments, and osseointegrated implants.3-8 Aids in pros-thesis orientation have included magnets, mouth sticks,and holders.1,9-11

Swartz et al1 reported on the use of samarium-cobaltmagnets for prostheses orientation and fixation. Multi-ple magnets were implanted in the patients’ subcuta-

neous tissues; mated magnets placed in the prostheses were used for retention and acted as points of orienta-tion during prostheses placement.1 Disantis9 describeda prosthetic auricular positioner, which consisted of amouth stick and rod that were keyed to the prosthesisand teeth. The patient would hold the stick in hismouth to position the prosthesis during placement.9

Lemon et al10 reported on magnetic placement andorientation of a facial prosthesis. This techniqueinvolved samarium-cobalt magnets embedded in a sili-cone prosthesis and counter magnets placed in a hold-ing device made from autopolymerizing acrylic resin.Magnets were placed in the prosthesis after processing,by removing a core of material with a punch biopsy,embedding the magnets, and replacing the core. Inaddition to facilitating prosthesis placement, the holderalso served as a stand during adhesive application. This

approach ensured that the adhesive would not be con-taminated by the patient’s fingers.10

This article describes a procedure for fabricating adevice to orient a small facial prosthesis.

PROCEDURE

In this procedure, only 2 magnets are required. The

first magnet is embedded in the prosthesis during pro-cessing, while the second magnet is placed in the device.This device extends past the margins of the defect and is

fabricated from clear acrylic resin to allow for visual andtactile sensory input during prosthesis placement. It also

serves as a stand during adhesive application.

1. Make the impression, master cast, sculpting, andmold in the usual manner.

2. Fabricate a duplicate cast for vacuum forming by making an impression of the master cast with irre-

versible hydrocolloid and inserting pieces of 30-lbthin nylon monofilament fishing line (Monofila-ment finishing line, Walker International, Detroit,Mich.) into the impression. Pour the cast in dentalstone. After the stone has set, remove the pieces of fishing line.

3. Select and mark a site on the master cast for place-ment of a small magnet (Jobmax No. 18, Jobmas-ter Co, Randallstown, Md.). The selected siteshould be within the margins of the prosthesis andhave adequate thickness to eliminate the magnetshowing through the surface of the prosthesis.

4. Place a 6-in. square piece of urethane liner (Ure-thane liner, Factor II, Lakeside, Ariz.) in a vacuumformer. Clean the surface with acetone and allow to dry.

5. Heat the sheet until it turns clear and glossy.6. Move the sheet away from the heat source and

apply S-2260 Prime Coat (S-2260 silicone primer,Dow Corning Co, Midland, Mich.) with a piece of cotton gauze held with forceps.11

7. Heat the urethane liner until it sags a half an inch.Then under vacuum, adapt it to the vacuum-form-ing cast.

Clear acrylic resin device for orientation and placement of a small facialprosthesis

Trakol Mekayarajjananonth, DDS, MS,a Michael L. Huband, DDS,b and Luis R. Guerra, DDS, MSc

Louisiana State University, New Orleans, La.

A small-sized facial prosthesis can be difficult to orient accurately in correct relationship to adefect. This problem may be reduced by embedding a magnet in the prosthesis and constructing amagnetic holding device from clear acrylic resin. This device can be used as a stand during adhe-sive application to reduce adhesive contamination and acts as orientation guide during prosthesisplacement. (J Prosthet Dent 2000;83:656-9)

aMaxillofacial Prosthetics Fellow, Medical Center of Louisiana, Den-tistry Division; and Lecturer, Department of Prosthodontics, Fac-ulty of Dentistry, Chulalongkorn University, Bangkok, Thailand.

bAssistant Professor, Medical Center of Louisiana.cProfessor, Department of Prosthodontics, School of Dentistry; and

Chief, Dental Services, Medical Center of Louisiana, and StanleyScott Cancer Center, New Orleans, La.

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8. Use cyanoacrylate (SuperGlue, Pacer Technology,Rancho Cucamonga, Calif.) to glue a small magnetto the urethane liner in the previously selected area(Fig. 1).

9. Apply a thin layer of Type A silicone adhesive(Type A silastic silicone adhesive, Dow CorningCo) to the urethane liner. Transfer the liner to themaster cast.

10. Pack the mold with silicone and process in theusual manner.

11. Recover the prosthesis from the mold and trim themargins. The magnet is now embedded within theprosthesis (Fig. 2).

12. Paint the counter magnet with Hold Adhesive (Tele-dyne Getz, Fort Collins, Colo.) and place the prosthe-

sis onto the master cast and attach the counter magnetover the area of the embedded magnet (Fig. 3).

13. Make an impression of the prosthesis and sur-rounding cast in irreversible hydrocolloid. Pourthe impression in dental stone. The magnet ispicked-up in the impression and the prosthesis istransferred to the resultant cast.

14. Wax the device on the cast to approximately 5 mmpast the margin of the prosthesis using pink base-plate wax (TruWax, Dentsply International Inc,

York, Pa.). Extend the pattern onto nonmovabletissues where possible (Fig. 4).

15. Create a hole in the center of the wax pattern. Thishole should be large enough to allow for thepatient’s finger to contact the prosthesis.

16. Flask the pattern and boil-out the mold. Thenusing cyanoacrylate, glue a magnet over the out-

MEKAYARAJJANANONTH ET AL THE JOURNAL OF PROSTHETIC DENTISTRY

JUNE 2000 657

Fig. 1. Magnet is glued to urethane sheet in previouslyselected area.

Fig. 2. Processed facial prosthesis with embedded magnet.

Fig. 3. Prosthesis positioned on master cast with countermagnet in place.

Fig. 4. Outline of device drawn approximately 5 mm beyondmargins of prosthesis.

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line of the magnet on the cast. Process in clearheat-cured acrylic resin (Hygenic denture resin,type I class I, The Hygenic Corp, Akron, Ohio).

17. Deflask, finish, and polish the device.18. Instruct the patient to place the prosthesis onto

the device and to use it as a holder during adhesiveapplication (Fig. 5).

19. Show the patient how to position the device overthe defect. The device is held with one hand andguided to place by visual and tactile input.

20. After positioning, the patient uses a finger to pushthe prosthesis against the defect, while removingthe positioning device (Figs. 6 through 8).

SUMMARY

A small-sized facial prosthesis can be difficult to ori-ent correctly to a defect. This problem may be

reduced through the used of a device made from clear

THE JOURNAL OF PROSTHETIC DENTISTRY MEKAYARAJJANANONTH ET AL

658 VOLUME 83 NUMBER 6

acrylic resin. In this technique, 2 magnets are used.One magnet is embedded in the prosthesis duringprocessing and the other magnet is embedded in the

device. The magnets hold the prosthesis against theacrylic resin device, which is used as a stand during

adhesive application, thus reducing retention prob-lems associated with adhesive contamination. Thin

prostheses may not be suited to this technique as abulk of material is required to mask the magnet. Thisdevice also acts as an orientation guide during pros-

thesis placement. It extends past the margins of thedefect and is fabricated from clear acrylic resin to allow

for visual and tactile sensory input during prosthesisplacement.

REFERENCES

1. Swartz BE, Udagama A, Spira M. Magnetic prostheses: an alternative fix-

ation and orientation method. Plast Reconstr Surg 1982;69:755-9.

Fig. 5. Prosthesis is held to device by magnets.

Fig. 6. Patient with small defect of right ala.

Fig. 7. Device is oriented over defect. Patient uses finger tohold prosthesis in place while removing device.

Fig. 8. Prosthesis placed in correct relationship to defect.

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MEKAYARAJJANANONTH ET AL THE JOURNAL OF PROSTHETIC DENTISTRY

JUNE 2000 659

2. Udagama A, Drane JB. Use of medical-grade methyl triacetoxy silanecrosslinked silicone for facial prostheses. J Prosthet Dent 1982;48:86-8.

3. McComb H. Osseointegrated titanium implants for the attachment of facial prostheses. Ann Plast Surg 1993;31:225-32.

4. Jacobsson M, Tjellström A, Fine L, Andersson H. A retrospective study of

osseointegrated skin-penetrating titanium fixtures used for retaining facialprostheses. Int J Oral Maxillofac Implants 1992;7:523-8.

5. Beumer J III, Ma T, Marunick MT, Roumanas E, Nishimura R. Restoration

of facial defects: etiology, disability, and rehabilitation. In: Beumer J III,Curtis TA, Marunick MT, editors. Maxillofacial rehabilitation: prosthodon-tic and surgical constructions. St Louis: Ishiyaku EuroAmerica, Inc; 1996.p. 377-454.

6. Javid N. The use of magnets in a maxillofacial prosthesis. J Prosthet Dent1971;25:334-41.

7. Nadeau J. Maxillofacial prosthesis with magnetic stabilizer. J Prosthet

Dent 1956;6:114-9.8. Udagama A, King GE. Mechanically retained facial prostheses: helpful or

harmful? J Prosthet Dent 1983;49:85-6.

9. Disantis WS. Technique for constructing a prosthetic ear positioner. J Pros-thet Dent 1985;53:282-3.

10. Lemon JC, Chambers MS, Wesley PJ, Martin JW. Technique for magneticplacement and orientation of a facial prosthesis. J Prosthet Dent 1996;75:

50-2.11. Udagama A. Urethane-lined silicone facial prostheses. J Prosthet Dent

1987;58:351-4.

Reprint request to:DR MICHAEL L. HUBAND

DEPARTMENT OF GENERAL DENTISTRY

BOX 127LOUISIANA STATE UNIVERSITY SCHOOL OF DENTISTRY

1100 FLORIDA AVE

NEW ORLEANS, LA 70119FAX: (504)619-8741E-MAIL: [email protected]

Copyright © 2000 by The Editorial Council of The Journal of Prosthetic Dentistry.

0022-3913/2000/$12.00 + 0. 10/1/106598doi:10.1067/mpr.2000.106598

The effects of tooth preparation on pressure measured inthe pulp chamber: A laboratory study Evans CDJ, Wilson PR. Int J Prosthodont 1999;12:439-43.

Purpose. This study investigated the pressure changes that occur in the pulp during dry and wettooth preparation using 2 types of burs.Material and methods. Twenty extracted premolars were obtained and randomly assigned to 2groups. All teeth were mounted on a pressure transducer. Tooth structure was removed in 0.1mm increments from the proximal surface of each specimen (group 1) with a diamond bur(Komet H31L 012 FG), first wet then dry, until pulp chamber exposure was evident. The sameexperimental procedure was repeated for group 2 specimens, using a cross-cut tungsten carbidebur (Komet H31L 012 FG). The pulp pressure change, temperature change, and handpiece posi-tion during specimen preparation were recorded.Results. Dry preparation pressure readings (–0.45 to 34.15 kPa) were much higher than thoserecorded for wet preparation (–1.45 to 2.50 kPa). The tungsten carbide bur demonstrated sig-nificantly less pressure than the diamond bur (α=.05) under both wet and dry conditions. When0 to 1 mm of dentin remained, dry preparation with the diamond bur generated a mean pulpalpressure of 12 kPa; dry preparation with the carbide bur generated a mean pressure of 6 kPa. Wetpreparation readings with the diamond and carbide burs, with the same dentin thickness remain-ing, were 0.6 kPa and 0.15 kPa, respectively. Preparation >2 mm from the pulp chamber gener-ated a mean 0.09 kPa increase in pressure. This increase was not changed by bur type or use of

water coolant. The temperature remained constant during wet and dry preparation with the car-bide bur, and during wet preparation with the diamond bur.Conclusion. When preparing teeth in vitro, with <2 mm of dentin remaining, significant pres-sure changes occurred within the pulp chamber. 25 References. —DL Dixon

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