TOOTHREDUCTIONGUIDE

6. Place the reduction guide in the patient’s mouth and accurately reshape the desired teeth (Fig. 4). 7. Narrow, polish, and smooth the occlusal surfaces of the odontoplasty, further reduce the teeth to receive crowns, and make temporary restorations. Vinyl polysiloxane may also be used for the construction of the reduction guide.

PROCEDURE Place polysiloxane putty (50/50) over the modified stone teeth, adapt it to both the facial and lingual aspects (no separating media is necessary), and allow it to set. 2. Reduce the height of the putty flush with the level of the occlusal surfaces of the altered teeth with a sharp knife. 3. Remove the guide from the cast in one piece and posi1.

Marginal

accuracy

of provisional

tion it over the natural teeth to indicate the necessary modifications (Figs. 5 through 7). REFERENCES 1. Ellinger CW, Rayson JH, Henderson D. Single complete dentures. J PROSTHET DENT 1971;26:1-10. 2. Sharry JJ. Complete denture prosthodontics. 3rd ed. New York: McGraw-Hill, 1974313-5. 3. Mann AW, Pankey LD. Use of Pankey-Mann instrument in restoring the lower posterior teeth. J PROSTHET DENT 1960;10:135-50. 4. Dawson PE. Evaluation and diagnosis and treatment of occlusal problems. St Louis: CV Mosby Co, 1974.

Reprint

D.D.S., M.S.D.,* and John B. Holmes,

University

San Francisco,

School

of Dentistry,

to:

restorative

Jack H. Koumjian, of California,

requests

DR. L. KIRK GARDNER SCHOLL OF DENTISTRY MEDICAL COLLEGE OF GEORGIA AUGUSTA, GA 30912-1250

San Francisco,

materials

D.D.S., M.Ed.** Calif.

Marginal integrity is an important quality in the provisional restoration. Previous studies on marginal integrity have presented conflicting results. In addition, newly available resins are making the selection of an accurate resin for provisional restorations difficult. The objective of this study was to evaluate the marginal accuracy of seven commercially available resins by using an established indirect technique, and to evaluate the effect of water absorption on polymerization shrinkage. Eight specimens of each material were tested under three conditions: immediately after polymerization, after 1 week of dry storage, and after 1 week of storage in room temperature water. Three materials, Duralay, Cold Pat, and Snap resins, produced statistically significantly superior marginal adaptation. Water absorption appeared to compensate for continued polymerization shrinkage. (J PROSTHETDENT~BB~;~~:~~B-~~.)

T

emporary coverage of a prepared tooth during various stages of treatment is an important step in the construction of fixed dental prostheses. Several factors affect the desirability of any specific provisional restorative material. These include resistance to fracture, marginal accuracy, color stability, wear resistance, tissue compatibility, ease of manipulation, and cost. The relative importance of most of these factors is directly related to the intended length of time that a provisional restoration is used.

This study was supported by a grant from the Academic Senate, University of California, San Francisco, Health Sciences Campus. Presented at the Pacific Coast Society of Prosthodontists meeting, Sun River, Ore. *Assistant Professor, Restorative Dentistry. **Clinical Professor, Prosthodontic Section.

10/l/18386

THE

JOURNAL

OFPROSTHETIC

DENTISTRY

Fig. 1. Stainless steel master die. Marginal accuracy ranks high on this list because good fit at the margins of a provisional restoration is essential to maintaining gingival health and protecting the tooth from physical, chemical, bacterial, and thermal injuries.lp 2

639

Fig. 2. Fig. 3. Fig. 4. Fig. 6.

Table

Experimental Stone model Experimental Stone model

model simulating simulating clinical model simulating simulating clinical

I. Provisional restorative materials tested

1 Snap (polyethyl methacrylate), Parke11 Bio-materials Division, Fermington, N.Y. 2 Trim (polyvinylethyl methacrylate), Harry Bosworth Co., Skokie, Ill. 3 Tru-Kit (methyl methacrylate), Harry Bosworth Co. 4 Protemp (Bis-aryl-composite), ESPE-Premier, Norristown, Pa. 5 Triad (light-activated composite resin), Dentsply Inc., York, Pa. 6 Duralay (methyl methacrylate), Reliant Dental Manufacturing Co., Alsip, Ill. 7 Cold Pat (polymethyl methacrylate), Motloid Co., Chicago, Ill.

Several studies have evaluated the techniques used for making provisional restorations. Barghi and Simmons3 recommended venting and relining all provisional restorations to increase marginal accuracy.3 Crispin et a1.4demonstrated the superiority of the indirect technique of mak-

clinical situation before tooth preparation. situation before tooth preparation. clinical situation after tooth preparation. situation after tooth preparation.

ing provisional restorations. Robinson and Hovijitra5 evaluated three provisional materials with the direct technique. Monday and Blai@ also found that margins made with the indirect technique were more accurate than those made with the direct technique. Tjan et al.’ evaluated four resins with the direct technique. Three of the four resins tested were found to be accurate in marginal adaptation. The conflicting results reported in these studies provide little guidance to the clinician in the selection of a resin. Furthermore, the newer composite and visible light-cured resins available should be evaluated so that the restorative dentist will have a basis for choice of a provisional material. This study evaluated in vitro the marginal accuracy of seven commercially available resins with an established indirect technique. In addition, the effect of water absorption on marginal accuracy was evaluated.

MATERIAL

AND

METHODS

A stainless steel master die was machined to the following dimensions: 5 mm height, 10 mm gingival diameter, 5degree taper, and 1 mm shoulder (Fig. 1). A flat surface

JUNE

1999

VOLUME

63

NUMBER

6

PROVISIONAL

RESTORATIVE

MATERIALS

MARGINAL ACCURACY PROVISIONAL RESTORATIVE

OF MATERIALS

69

m ii t-

q 1 WK AIR

100

a

5

75

8 5

50

’ii

25

TRUKIT

Fig.

Table

TRIAD

TRIM

PROTEMP

SNAP

1 WK WATER

COLDPAC

DURALAY

6. Marginal discrepancy under three conditions.

Marginal discrepancy under three test conditions

II.

Material

Immediate

(n = 8)

Tru-Kit Triad Trim Protemp Snap Cold Pat Duralay

1 Wk

JOURNAL

OF PROSTHETIC

air

1

Wk water

pm

SD

flm

SD

pm

SD

94

24 24 23 19 27 27 25

122 110 89 97 61 59 43

26 33 17 26 27 26 27

90 80 91 91 58 39 24

15 28 19 17 21 19 20

93 80 70

59 55

39

machined at a 30-degree angle to the long axis was made on one side of the die to help standardize the crown placement. Four points of reference were placed on the mesial, distal, facial, and lingual gingival finishing lines so that the measurements made were consistent. The experimental model, simulating the clinical situation before and after tooth preparation, consisted of three metal dies with the master die in the middle. A full cast crown was cemented over the master die to simulate the unprepared tooth (Fig. 2). No measurable gaps were observed at the margin of the cemented crown. An impression of this experimental model was made using a polyvinyl siloxane material (Express, 3M Co., St. Paul, Minn.). A stone model, simulating the tooth before preparation, was obtained from the impression (Fig. 3). This model was used to prepare a stent. The cast crown was then removed from the master die (Fig. 4). Seven impressions of the experimental model were made with the same impression material. Eight stone dies were obtained from each of the seven impressions for a total of 56 dies (Fig. 5). Each of the seven provisional resins (Table I) were pro-

THE

IMMEDIATE

DENTISTRY

portioned, manipulated, and timed according to the manufacturer’s instructions. Resin-filled stents were fitted over the lubricated dies and stabilized with rubber bands. Eight provisional restorations were made from each resin. Five of the materials were cured in a pressure pot at 30 psi for 10 minutes. Triad resin was cured in a light-curing unit (Triad, Dentsply Int., York, Pa.) according to manufacturer’s instructions and Protemp resin was cured for 10 minutes on the bench. After curing, each restoration was trimmed, excess material was removed, and the margin was finished. The crown was seated by hand pressure on the master die. All measurements of the provisional crowns were made by using a measuring microscope at the original magnification of X100. Gaps between the margin of the restoration and the finish line of the preparation were measured at the four reference points. The measurements of each provisional restoration previously marked on the mesial, distal, facial, and lingual finish lines were measured under three different conditions: immediately after seating, after 7 days storage in air at room temperature, and after 7 days storage in water at room temperature.

641

RESULTS The results are presented in Fig. 6 and Table II. All of the materials demonstrated some dimensional change from the immediate group measurements. All of the l-week dry storage values were greater than the immediate values. With the exception of Trim and Protemp resins, all l-week wet storage values were less than the immediate values. Analysis of variance (ANOVA) and least squares means were used to establish the statistical significance among seven resins under three conditions.

DISCUSSION The most clinically relevant model is, of course, the l-week wet storage model. Duralay, Cold Pat, and Snap resins were clinically acceptable because of the minimal marginal gap produced (24 to 57 pm range). They had significantly lower marginal discrepancy when compared with Tru-Kit, Triad, Trim, and Protemp resins (30 to 90 pm range). The effect of continued polymerization was investigated by comparing the marginal fit of the crowns on the die immediately after fabrication with the fit after storage in air at 37’ C for 1 week. The gap distance increased for all materials during 1 week of storage in air. This increase was probably the result of continued polymerization of resin. The increase was statistically significant for Trukit, Triad, Trim, and Protemp resins and not statistically significant for the remaining materials. The effect of water absorption on the fit of the crowns was investigated to determine whether water absorption compensates for polymerization shrinkage. The decreasing gap sizes are probably indications of such compensation after storage in water for 1 week. On the other hand, water absorption did not appear to compensate for the polymerization shrinkage of the Trim and Protemp resins. It is ad-

642

visable to store the provisional crowns in water whenever practical before cementation to provide better marginal adaptation at the time of cementation.

CONCLUSIONS Seven provisional restorative materials were tested immediately after fabrication, after storage for 1 week in air, and after storage for 1 week in water. The following conclusions were made: 1. The best result was obtained with Duralay resin, followed by Cold Pat and Snap resins. These three materials had significantly less marginal discrepancy compared with the other resins tested. 2. All of the materials showed evidence of continued polymerization shrinkage after storage in air for a week. 3. Water absorption compensated for polymerization shrinkage in all of the materials except Trim and Protemp resins. REFERENCES 1. Krug RS. Temporary 1975;19:313-20. 2. Kaiser DA. Accurate

resin crowns acrylic

and bridges.

resin temporary

Dent Clin North

restorations.

Am

J PROSTHJZT

DENT 1978;39:158-61.

3. Bargbi N, Simmons EW. The marginal integrity of the temporary acrylic resin crown. J PROSTHET DENT 1976;36:274-7. 4. Crispin BJ, Watson JF, Caputo AA. The marginal accuracy of treatment restorations: a comparative analysis. J PROSTHET DENT 1980;44:283-90. 5. Robinson FB, Hovijitra S. Marginal fit of direct temporary crowns. J PROSTHET DENT

6. Monday crowns.

1982;47:390-2.

JJ, Blais D. Marginal J PR~~THET

adaptation

of provisional

acrylic

resin

DF.NT 1985;54:194-7.

7. Tjan AH, Tjan AH, Grant BE. Marginal accuracy composite crowns. J PROSTHET DENT 1987;58:417-21.

of temporary

Reprint requests to: DR. JACK H. KOUMJIAN SCHOOL OF DENTISTRY UNIVERSITY OF CALIFORNIA SAN FRANCISCO, CA 95153-0758

JUNE

1990

VOLUME

6.3

NUMBER

6

Marginal accuracy of provisional restorative materials.

Marginal integrity is an important quality in the provisional restoration. Previous studies on marginal integrity have presented conflicting results. ...
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