FIVE-YEAR ASSESSMENT OF FIXED PROSTHODONTICS

13. Glantz, P-O., Strandman, E., and Randow, K.: Unpublished data.

14. Nilner, K., Glantz, P-O., Ryge, G., and Sundberg, H.: Oral galvanic action after treatment with extensive metallic restora- tions. Acta Odontol Stand 40:381, 1982.

15. Axell, 1‘.: A prevalence study of oral mucosal lesions in an adult Swedish population. Odont Revy 27(Suppl), 1976.

16. Agerberg, G., and Carlsson, G. E.: Functional disorders of the masticatory system. I. Distribution of symptoms according to age and sex as judged from investigation by questionnaire. Acta Odontol Stand 30~597, 1972.

17. Hansson, T., and Nilner, M.: A study of the occurrence of symptoms of diseases of the temporomandibular joint masticatory

musculature and related structures. J Oral Rehabil 2:313, 1975.

18. Helkimo, M.: Epidemiological surveys of dysfunction of the masticatory system. Oral Sci Rev 1:54, 1976.

We acknowledge the editorial assistance provided Ijy Hilary Prit- chard, Senior Editor, Department of Restorative Dentistry, University of California, San Francisco.

Keptnt requests to: DR. GUNNAR RYCE 49 GRACELANI) DRIVE SAN RAFAEL, CA 94901

New irreversible hydrocolloid silicone impression material

Wilmer B. Eames, D.D.S.,* and Clifford S. Litvak, D.D.S., M.S.** University of Colorado, School of Dentistry, Denver, Colo.

A lginate (irreversible hydrocolloid) has not been considered the patrician of impression materials since its introduction prior to World War II when agar from Japan became scarce.’ It has been used primarily for opposing casts and study models. The irreversible hydro- colloid materials are used in removable partial denture prostheses, in orthodontics, and to a limited extent in fixed partial prosthodontics.’

Prior to the use of alginates, agar hydrocolloid had been the accepted precision impression material since it was described in 1 937.3 The clinical use of hydrocolloid impression materials results in a high degree of accuracy and detail reproduction. The material had long been acceptable for making precision castings.

In addition to the use of irreversible hydrocolloid and hydrocolloid individually, several authors have described the combined use of the two materials.4-6 The injection of reversible hydrocolloid was thought to provide the neces- sary details while alginate served to unite them to the tray.

With the convenience of elastomeric materials in both packaging and mixing, a trend to depart from the heated

Presented at Ihe American Academy of Restorative Dentistry, Chicago, Ill.

*Professor Emeritus, Emory University, School of Dentistry, Atlanta, Ga., and Visiting Professor, University of Colorado.

**Clinical Instructor, University of Colorado.

conditioner required for hydrocolloids occurred in favor of a simple paste/paste system. However, a recent survey revealed that hydrocolloids ranked third in preference by nearly 4000 dentists.’

The disadvantages of hydrocolloids include the neces- sity for preparation with special heating conditioners as well as their instability and the need for immediate pouring. This disadvantage is not confined to hydrocol- loids. Both rubber base and silicone materials are unstable unless poured immediately.8 Conversely, polyethers and polysilicones are stable for several days prior to pouring.8

Consequently, the hydrocolloids have regained favor and are acceptable when compatible gypsum die materials are used. Some gypsums are not compatible with hydrocolloids or with powder/water alginates.9~‘o

MATERIAL AND METHODS

The present study compared a reversible hydrocolloid, Surgident (Columbus Dental Mfg. Co., St. Louis, MO.), and an irreversible hydrocolloid powder/water system, Jeltrate (L.D. Caulk Co., Milford, Del.), with a new irreversible hydrocolloid/silicone, Ultrafine (batch No. 811005, Buffalo Dental Mfg. Co., Brooklyn, N.Y.), (Fig. l), heavy and light bodies, manufactured in paste/catalyst form. Humectants are used in its formu- lation to stabilize the surface detail and help prevent syneresis, which occurs with powder/water irreversible

THE JOURNAL OF PROSTHETIC DENTISTRY 479

EAMES AND LITVAK

Fig. 1. Heavy-bodied Ultrafine alginates/silicone p%.te.

hyrfrocolloids. It is thixotropic, pleasant tasting, and

mixes readily with its catalyst counterpart. The heavy- body material is mixed in a bowl, and the thinner wash material is measured and mixed on a pad.

The study also compared physical properties, repro- duction of detail, and the influence of I%rafine on two qypsurn products for detail reproduction.

Die-Keen dental stone (Columbus Dental Mfg. Co.) provides maximum detail reproduction with hydrocol- ioids and has high scrape resistance.” It was used as the standard die material in a comparison of unmodified alph,l calcium sulfate hemihydrate (the standard for :2DA testing), because it was found to be more compar- ihlc than other die materials tested.‘” In all instances, potassium sulfate (2%) was used for a 15-minute bath prior to pouring the hydrocolloid specimens. as recom- mended by the manufacturers.

Both American Dental Association (ADA) specifica- tion No. 11 for hydrocolloids and specification No. 18 for alginates were used for comparison in this study, because hydmcolloid specifications are more stringent and Ultra- line ts claimed to be comparable to hydrocolloids.

Special attention should be given to a recent brief report of an “alginate substitute,” which was the name adopted for the original heavy-bodied product.” The subsequent light-bodied (syringeable) material was not tested but was marketed. It has been used for more than 3 years for precision castings. Because ofthe word “silicone’” 1 n the product description, the ADA C.ouncil evaluated this Ijroduct by means of the nonaqueous elastomeric specifica- uon No. 19 and compared it with a commercial silicone iuhber product. I.Tltrafme was not intended to meet specification No. 19, although it fared well when poured immediately and when not tested after 24 hours. Ultrafine is an irreversible hydrocolloid/silicone polymer material and not a silicone rubber (elastomer), with which the ADA

Fig. 2. Clinical models. Top, Impression made with Ultrafine heavy-body. Bottom, Impression made with hydrocolloid heavv-body.

report compared it. ’ It is not presented as capable of meeting the 24-hour requirements of specification No. 19. Immediate pouring of Ultrafine (and other aqueous materials) is essential. When this requirement is followed, detail reproduction and compatibility with gypsum were well within specifications.

RESULTS

In the detail reproduction tests, it was found that even the heavy-bodied irreversible hydrocolloid/silicone product was often comparable with heavy-bodied hydro- colloid (Fig. 2). The syringeable or “wash” consistency of Ultrafine was found under most conditions to be

superior to light-bodied hydrocolloid. Fig. 3, A, shows a macrophotograph of the 75, 20, and 50 hrn lines of the light-body Ultrafine, and Fig. 3, R) demonstrates the virtual lack of the 20 km line reproduction with light- bodied hydrocolloid.

Table I presents the data for Ultrafine irreversible hydrocolloid/silicone. %Jeltrate powder/water alginate, and Surgident reversible hydrocolloid, by comparing ADA specifications No. 11 for hydrocolloids and No. 18 for alginates.

When the setting-time category in the specifications is considered. Ultrafine can be ad.justed by the addition of

480 OCTOBER 1984 VOLUME 52 NUMBER 4

NEW ALGINATE/SILICONE IMPRESSION MATERIAL

Fig. 3. A, Reproduction of 75,20, and 50 Mm lines by light-bodied Ultrafine poured in Die-Keen. B, Reduced detail reproduction with light-bodied hydrocolloid poured in Die-Keen.

more or less catalyst to accommodate the dentist. This body and the hydrocolloid were within this specifica- does not change the consistency or viscosity of the tion. material. Powder/water irreversible hydrocolloids like For compressive strength, all materials exceeded both Jeltrate can be altered by varying the temperature of the specifications No. 11 and No. 18. Ultrafine light-body water. exceeded the hydrocolloid specification fourfold. This

The permanent deformation limit of 1.5% for hydro- property relates to tear resistance. colloid was exceeded by Jeltrate, but Ultrafine light- For compressive strain, both alginates met specifica-

THE JOURNAL OF PROSTHETIC DENTISTRY 481

EAMES AND LITVAK

Fig. 4. Thixotropic characteristic of Ultrafine shown on maxillary complete arch impression.

tion No. 18, and the heavier-bodied materials were well within hydrocolloid specifications.

DISCUSSION

it should be noted that the specifications permit some elast.omeric materials to shrink up to 1% in a 24-hour period ’ ” IJltrafine falls within this range when poured immediately.

In a concurrent study of mixing methods, Ultrafine :u:th least affected by different mixing techniques and showed the least difference of any of the materials with : acuum, hand-mixing in a rubber bowl, or by a mechan- iiai rotating bowl. Reducing bubbles is an inherent problem with all viscous materials.

f:linical experience has shown the thixotropic charac- teristic. of Ultrafine (Fig. 4) to be particularly advanta- r;cous when making maxillary complete arch impres- ‘,o!r’,

STONE DIES

.“\ previous study reported that some gypsum stone die materials are more compatible with hydrocolloids than ot!~ers.” This phenomenon did not always appear to be a problem with Ultrafine. Fig. 5, A and R, are examples of ii)ie Keen that exhibit a smoother surface texture than l/‘&-Mix. This may be a characteristic of the stone itself rnther than the influence of the impression material. Soaking hydrocolloids in potassium sulphate provides a better surface with some die materials, but it does not influence Illtrafmr.

The technique for use of this new irreversible hydro- ;,olloid is simple. The heavier paste material is mixed with its catalyst in a rubber bowl. The thinner wash material is proportioned and mixed on a pad and injected into rhe preparation (Fig. 6). The filled tray is carried into place (Fig. 7) and held for 3 to 3’N minutes before removal (Fig. 8)

482

Fig. 5. Surface texture differences of A, Die-Keen and B, Vel-Mix when poured against Ultrafine impression.

Fig. 6. Injecting thin paste with syringe

Fig. 0, A, N, and i., demonstrates the relative seating ability of castings made on a steel die designed for this purpose. The comparative materials were a vinyl polysi- ioxane, Reprosil (I. D. Caulk Co.), Surgident, and Illtrafine. Die spacing was used routinely.

IICTOBER 1984 VOLUME 52 NUMBER .I

NEW ALGINATE/SILICONE IMPRESSION MATERIAL

Fig. 7. Filled tray is held for 3 to 3% minutes.

Fig. 8. Impression showing light- and heavy-bodied Ultrafine.

Fig. 10 shows a typical mesial-occlusal-distal inlay on a second premolar completed in the manner described by the Chairman of the Operative Division at the Universi- ty of Colorado. He reported that the procedure was routinely successful.

Painting a coat or two of die surface hardener (Stone Die & Plaster Hardener Resin, George Taub Products and Fusion Co., ,Jersey City, N.J.) will increase the scrape or abrasion resistance and produce a considerably smoother die. The film thickness is negligible. This hardener is an acrylic solution that penetrates the surface of the die to leave a smoother surface prior to waxing. Cyanoacrylates are sometimes used for this purpose but are considered hazardous because they adhere to the fingers.

The manufacturer of Ultrafine suggests the use of a silicone rinse, Ultra-Wet (Buffalo Dental Dental Mfg. Co., Brooklyn, N.Y.), to facilitate removal and help prevent tearing. This gives a slight loss of detail, just as there is when preparations are wet with viscous saliva. Sticking is not a major problem but does happen occasionally. The rinse is readily available.

Fig. 9. Seating ability of castings made from A, Repro- sil, B, hydrocolloid, and C, Ultrafine. Die spacing was used routinely.

Fig. 10. Clinical result with Ultrafine for mesial-occlu- Sal-distal inlay. (Photo courtesy of Dr. Ralph Lambert.)

THE JOURNAL OF PROSTHETIC DENTISTRY 483

EAMES AND LITVAK

Table I. Properties of Ultrafine, a powder/water alginate, and a hydrocolloid judged by ADA specifications No. 11 and No. 18

-.~- ..- - ~- --.- _..~ -...-..-. Alginates”

.--__--.- -. ~~..~ Ultrafine Ultrafine

light heavy Powder/ Property body body water Hydrocolloidt

Setting time (min.j 3.5 3 2.5 2.5.3$ Permanent deformation ((&) 1.12 1.92 1.93 1.0 Compressive strength &m/cm’1 10486 9559 7056 6439 Compression strain (‘5) 18.7 12.5 13.1 5.6

CONCLUSION

Ultrafine will not replace the elastomeric materials because the latter are tougher and do not tear as readily. Its clinical use for almost 4 years, supported by our laboratory and clinical testing, has shown that Ultrafine could well replace hydrocolloids and is more convenient to use in its paste form.

4.

,

There are disadvantages to all types of materials, and irreversible hydrocolloid/silicones may not be preferred by all clinicians; but the concept is unique. The irrevers- ible hydrocolloid and agar materials cannot be plated., but surface die hardeners are advantageous.

In general, the paste system is more convenient and has better physical properties than the water/irrevers- ible hydrocolloid material tested. The cost of the paste system is comparable to the powder/water product, less costly than hydrocolloid, and more convenient. The paste system is also appreciably less costly than the elastomer- its, particularly the new polysiloxanes. Cost should not, of course, be the prime consideration.

It is expected that the use of Ultrafine may be extended to areas that have not been acceptable to powder/water materials: for master impressions for complete and partial dentures and for highly detailed opposing costs in prosthodontics, as well as for orthodon- tic working casts. Ultrafine has an excellent potential for precision castings in restorative dentistrv.

! I

i ?.

REFERENCES

Appleby. I). C:.. Cohen. S. R., Racowsky, I,. P.. and Mmgledorfi’.

I<. K.: 7‘he combined revrrsible h);drocolloid/irrr\ersible imprrv

sions cv~wm (:linical q@ication. .J PINXIWET th.N I’ 46:48.

1981.

OCTORER 1984 VOLUME 52 NUMBER 4