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Maxillofacial prosthetics

Surface characterization of the siliconerubber prosthesisStephen 0. Bartlett, Captain DC) USN,* levy Y. Pineda, Chief, USN,**and Dorsey J. Moore, Commander DC) USN***Bethesda, Md.

.Lh e prosthesis that replaces facial tissues must meet stringent standards withrespect to appearance and physical properties. Various materials and fabricationmethods have been used throughout the history o f maxillofacial prosthetics.Currently, silicone rubber, either heat vulcanizing or room-temperature vulcanizing,is, frequently used. Vinyl plastisol preparations have the advantage of being easilycured with varied coloration intrinsically incorporated in the prosthesis to simulatethe natural appearance of the skin. Silicone rubber can also be intrinsically coloredbut only in a single base color, without variations. Regardless of the material used,it. is an advantage to be able to alter the color o f the finished prosthesis. Even themost talented operator occasionally needs to make such changes.

For several years, room-temperature-vulcanizing silicone rubber? has been usedat the United States Naval Dental School, National Naval Medical Center, forfabricating prostheses. Until recently, we were extrinsically altering the color ofthe prosthesis by adding a new layer of the same type of rubber to the surfaceand then by spraying the material with a catalyst. All too frequently, as describedby Schaaf,l the bond between the prosthesis and the extrinsic material was weak.The patient would peel away the outer layer of silicone rubber when cleaning andhandling the prosthesis. Owing to a lack of translucency and depth of coloration, theprosthesis did not always appear as natural as was desired. Because of these experi-ences, we developed a modification of the technique for extrinsic coloration. We nowuse silicone medical adhesiveg rather than the ordinary silicone rubber for the addi-tional layer of material.-- The opinions and assertions contained herein are those of the authors and are not to bemnstrued as official or as reflecting the views of the Navy Department or the Naval Serviceat large.

*Head, Prosthodontics Department.**Senior Laboratory Technician, Maxillofacial Prosthetics Division.***Formerly Chief, Maxillofacial Prosthetics Division.tSilastic 382 or 502, Dow Corning, Inc., Midland, Mich.:Silastic Adhesive Type A, Dow Corning, IIK.~ Midland, Mich.

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Fig. I

70 Bartlett, Pineda, and Moore J. Prosth. Dent.January, 1971

MATERIALS AND METHODSThe prosthesis is constructed in the base shade employing the technique of Firtell

and Bartlett.* After it is found to be satisfactory in contour and shade, it is thoroughlycleaned with chloroform to remove all contaminants from the surface. The portionof the surface to be characterized should not be touched with the fingers. A con-venient handle for holding the prosthesis while it is being cleaned and tinted canbe made. Acrylic resin is poured into a disposable plastic syringe, and the heads ofstraight dressmaker pins are embedded in the resin. The prosthesis is speared onits inner surface by the projecting pin points Fig. 1) .

The tinting material is prepared by first thinning silicone Type A medical ad-hesive with xylene to the consistency of paint approximately equal parts of siliconeand xylene are used). Small amounts of the thinned adhesive are placed in in-dividual medicine cups, and each is tinted with a different inorganic pigment, whichis mulled into the mix with a spatula Fig, 2). The adhesive is applied to the surfaceof the prosthesis with cotton swabs Fig. 3) . Brushlike strokes are sufficient where lightshades are required. To obtain deep shades, as for freckles, a buildup can be achievedwithout fear that the material will not be cured. The reason is that the Type Aadhesive is autocatalytic as it comes from the manufacturer. Therefore, it does notneed to be sprayed with a separate catalyst, which might not permeate the thickestparts of the material. Colored flocking can be added if indicated. The entire tintingprocess takes about 15 to 20 minutes.

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p1grg 1u Surface characterization of rubber prosthesis 71

Fig. 3. The tinted adhesive is being applied to the surface of the prosthesis.

After several minutes, when the surface has reached the tacky stage, a skinliketexture can be obtained by dabbing a patch of lint-free gauze over the area. Oncethe desired characterization is obtained, the prosthesis is set aside for 30 to 45minutes to complete the cure. During the process, the xylene will volatilize, leavinga desirable dull surface. As the Type A adhesive is translucent, the effect will be quitelifelike.LIISCUSSION

This tinting procedure requires less time and effort than the various methodspreviously used. The strength of the prosthesis is improved by the inherent qualitiesof the Type A adhesive. There is a complete cure of the surface and no buildupof catalyst to be concerned about. Also, there is no tendency for the extrinsic colora-tion to peel free, because the adhesive is bonded to the base prosthesis very tena-ciously. Limited experimentation has shown that the adhesive can be used with equalsuccess for tinting the prosthesis fabricated of heat-vulcanizing silicone rubber.C:ONCLUSION

A modification of the technique for tinting silicone extraoral maxillofacialprostheses has been described. This is a simple, effective means of realisticallycoloring the silicone prosthesis.References1. Schaaf, N. G.: Color Characterizing Silicone Rubber Facial Prostheses, J. PROSTH. DENT.24: 198-202, 1970.2. Firtell, D. N., and Bartlett, S. 0.: Maxillofacial Prostheses: Reproducible Fabrication, J.

PROSTH. DENT. 22: 247-252, 1969.