near dimensional variability recessing and in water Donna L. Dixon, Karl G. Ekstrand, University Dentistry,

of Iowa, Lexington,

DMD,a DDS, College Ky.

Larry PhDC

of Dentistry,

C. Breeding, Iowa


of three storage DMD,b



base res


and University

of Kentucky,



It has been shown that denture base resins shrink during curing and expand during storage in water. This investigation measured and compared linear dimensional changes of three denture base resins that occurred during processing and after storage in water for 30,60, and 90 days. Triad, Accelar 20, and Lucitone 199 longand short-cured resins were studied, and it was found that Accelar 20 resin exhibited the least curing shrinkage and Lucitone 199 resin short-cured exhibited the most. However, no significant differences occurred between the groups. After 90 days of water storage, the only resin that exhibited a shrinkage from the processed state was Accelar 20. All of the expansion or shrinkage changes were so small that they were not statistically significant and should not be clinically detectable. (J



rom the mid 1850s to the 192Os, rubber was the most satisfactory denture base material available. After World War I, dentists began to search for more esthetic alternatives to this material. It was thought that methyl methacrylate resins could be satisfactorily used in denture

aAssistant Professor, Department of Prosthodontics, University of Iowa, College of Dentistry. bAssociate Professor, Department of Oral Health Practice, University of Kentucky, College of Dentistry. CAssistant Clinical Professor, Department of Prosthodontics, University of Iowa, College of Dentistry.



1. Stainless steel mold used for specimen fabrication.

base fabrication, and investigators began to study these resins. Sweeney1 compared various resins to denture rubber by examining certain physical and mechanical properties of the different materials. One of the properties examined was linear dimensional change after curing, and two methods for measuring this change were developed and described. The resins were all found to shrink during the curing process. However, on immersion in water, the resins were found to expand. Sweeney et a1.2 showed that the water sorption by early methyl methacrylate denture base materials caused an increase in posterior denture dimension. These dentures, on drying, however, were found to generally decrease in


2. Duplicate

of stainless


steel mold formed




in stone.







I. Mean



Resin brand

dimensions Sample NO.

of each resin Preprocessed (mm)

Processed (mm)

water (mm)

60-Day storage

water (mm)

go-Day storage

water (mm)

Accelar 20

1 2 3 4 5 6

44.239 43.132 42.244 45.169 45.731 48.396

43.829 42.951 41.963 45.054 45.583 48.135

43.850 42.835 41.910 44.947 45.494 48.078

43.862 42.852 41.913 44.852 45.540 48.062

43.870 42.827 41.864 44.855 45.566 48.071

Lucitone 199 short-cured

1 2 3 4 5 6

35.922 36.858 36.588 41.477 43.234 42.926

35.751 36.529 36.479 41.316 43.141 42.354

35.729 36.192 36.351 41.349 42.966 42.681

35.771 36.511 36.418 41.244 42.870 42.679

36.384 36.497 36.342 41.234 42.986 42.721

Lucitone 199 long-cured

1 2 3 4 5 6

43.955 42.577 41.214 40.232 39.931 40.001

43.704 42.203 41.049 39.962 39.740 39.808

43.754 42.404 41.135 39.957 39.814 39.794

43.663 42.353 41.132 39.931 39.753 39.807

43.665 42.390 41.081 39.934 39.799 39.809


1 2 3 4 5 6

41.993 43.640 44.012 40.074 40.481 42.035

41.746 43.310 43.824 39.807 40.282 41.794

41.698 43.409 43.981 40.027 40.405 41.915

41.777 43.495 43.964 39.978 40.445 41.992

41.619 43.478 43.977 39.965 40.450 41.920

dimension. Two maxillary complete dentures actually worn by patients were found to increase in posterior dimension by approximately 0.27 mm during an initial 4-month period, after which dimensional stability was reached. Woefel et a1.,3 Skinner and Cooper,4 and Sweeney5 concluded that the dimensional expansion of denture base resins caused by water sorption usually compensates in part for the processing shrinkage. In another investigation by Mowery et al.,‘j during the first month after curing, denture base resins worn by patients were shown to exhibit the greatest dimensional change. After approximately 2 months, no further significant dimensional change was shown to occur.3, 6 Many new resins have been introduced to dentistry for use as denture bases. It was the purpose of this investigation show and compare the amount of linear dimensional change that occurs in three of these resins after curing. In addition, the linear dimensional changes occurring in these resins after storage in water over time were recorded and compared.




A stainless steel mold containing five compartments each 65 mm long, 10 mm wide, and 3 mm thick was fabricated


30-Day storage




(Fig. 1). With the use of a polyvinyl siloxane impression material (Reprosil, L. D. Caulk Co./Dentsply Intl., Milford, Del.) in a custom acrylic resin tray, an impression was made of three compartments in the metal mold, and master casts were made from this impression with improved dental stone (Fig. 2). Wax was then placed in each stone compartment. Three wax dimples were made in each block with a number eight round bur. Small dimples were also made in each wax block to provide for measurement orientation and block identification later. A traveling microscope (Mitutoyo Mfg. Co., Ltd., Japan) was used to measure the total distance from the uppermost dimple to the lowest dimple to the nearest 0.001 mm. Because of the inability of the microscope to measure distances over 25 mm, it was necessary to measure distance AB (the lowest point of the uppermost dimple to the highest point of the middle dimple) then distance BC (the highest point of the lower most dimple to the highest point of the middle dimple), and finally add the two measurements to obtain a total linear distance value AC (Fig. 3). Three such linear dimensional measurements were made of each wax block by one investigator (DLD). From these three measurements, a mean linear dimensional value for each block was calculated. The casts with the wax blocks were then invested in denture flasks.



Accelar 20

Lucitone 199 short-cured

Lucitone 199 long-cured of lin-


Fig. 4. Cured Triad odontic wires.

resin specimen

with embedded


Six such blocks were processed with Lucitone 199 resin (Dentsply Intl., York, Pa.) according to manufacturer’s instructions by using the long-cure method, and six blocks were processed by using the short-cure method. Six blocks were also processed by using Accelar 20 fast heat-cured polymethyl methacrylate resin (Columbus Dental Co., St. Louis, MO.). These samples were made according to manufacturer’s instructions by the 20-minute cure method. Triad visible light-activated resin (Dentsply International, York, Pa.) was also used to prepare six samples the same size as those made from the Lucitone 199 and Accelar 20 resins. These samples were adapted and cured in the stainless steel mold from which the other master casts were made. Because of the flow properties of the uncured Triad denture base material (Fig. 4), three rectangular orthodon-


Mean change (mm)





Resin brand

of points used in measurement


Calculated mean and mean percent each resin group



Fig. 3, Illustration ear dimension.


Mean change

DWP DW30 DW60 DW90 DP30 DP60 DP90

-0.233 -0.300 -0.305 -0.310 -0.067 -0.072 -0.077

-0.150 -0.161 -0.174

DWP DW30 DW60 DW90 DP30 DP60 DP90



DWP DW30 DW60 DW90 DP30 DP60 DP90

-0.241 -0.175 -0.212 -0.205 0.065

DWP DW30 DW60 DW90 DP30 DP60 DP90

-0.245 -0.133


-0.525 -0.671 -0.682 -0.695



-0.253 -0.140 -0.050 -0.014

-0.636 -0.334 -0.148 -0.035



-0.584 -0.425 -0.511 -0.496





0.086 -0.587 -0.316 -0.231 -0.327 0.270 0.355 0.258


-0.138 0.112 0.148 0.108

DWP, Difference between wax (or uncured Triad) and processed samples; DW30, difference between wax (or uncured Triad) and samples; DW60, difference between wax (or uncured Triad) and 60-day samples; DW90, difference between wax (or uncured Triad) and go-day samples; DP30, difference between processed and 30-day samples; DP60, difference between processed and samples; DP90, difference between processed and go-day samples.

tic wires were embedded in each block of uncured Triad resin, and linear dimension AC was calculated as previously described for the dimple method. Three measurements were made for each sample, and a mean total linear dimension value was obtained. Orientation and identification dimples were placed in each Triad block after the curing cycle. All samples within each resin group were made from the same batch number. Immediately after processing, all samples were measured by the same investigator (DLD) using the methods described. To determine and compare the effect of water sorption on the various resins, each processed block was stored in deionized distilled water at 37’ C, and measured again at 30 days, 60 days, and 90 days, as described (Table I).











r......+rAccelar m--m


C+ - - -oLucitone

20 199 Short-Cured 199 Long-Cured







5. Percent

change in linear

RESULTS The mean linear dimensional change in millimeters and the mean percentage change during each time period was calculated for each resin (Table II). Because the distance AC varied from specimen to specimen, percent changes in linear dimension were calculated for between-group comparison. A repeated measures ANOVA model (BMDP2V, BMDP Statistical Software, Inc., Los Angeles, Calif.) with groups as a between-specimen factor, time as a within-specimen factor, and the linear dimensional percent changes with the preprocessed or the processed lengths as the base value showed no significant differences (p < 0.01). A graph depicting the percentage change in linear dimension versus time of the four resin groups is shown in Fig. 5. The Lucitone 199 short-cured resin samples showed the greatest linear dimensional variability during water storage, and Accelar 20 resin samples showed the least. The Lucitone 199 short-cured and Accelar 20 resin samples showed a decrease in the mean percentage change in linear dimension (resin shrinkage) from processing to 30 days of water storage, whereas the Lucitone 199 long-cured and Triad resin specimens showed an increase in mean percent






over time in water


change in linear dimension from processing to 30 days of water storage. From 30 to 60 days of water storage, the mean percent change in linear dimension of the Lucitone 199 short-cured resin specimens and the Triad resin specimens increased. The Accelar 20 and Lucitone 199 longcured resin specimens decreased in percent change in linear dimension during this time period. Only the Lucitone 199 long- and short-cured resin specimens increased in mean percent change in linear dimension from 60 to 90 days. The other resins exhibited a decrease in percentage change during this time period. Over time, none of the resins returned to the exact linear dimension recorded after processing; however, the linear dimension of Lucitone 199 long-cured resin specimens at 90 days was closest to the processed linear dimension. None of the resins returned to the linear dimension recorded before processing.

DISCUSSION The results from this study indicate that Lucitone 199 short- and long-cured, Accelar 20, and Triad denture base resins change in linear dimension during curing. Lucitone 199 short-cured specimens exhibited a greater mean percent of curing shrinkage than did the other specimens, with



Accelar 20 resin specimens exhibiting the least shrinkage. However, there was no significant difference between any of the resins. From processing to 30 days in water storage, Accelar 20 resin samples exhibited shrinkage in linear dimension, whereas the Triad samples exhibited expansion in the mean linear dimension at this time interval and from processing to 60 days. It has been shown, however, that the small changes noted here could not be detected clinically.1-3,


It was expected that expansion would occur when a dry denture base resin was soaked in water for an initial period as did the Lucitone 199 long-cured and Triad resin specimens. It was not expected, however, that the other two resins would exhibit shrinkage during the initial soaking period. Perhaps residual monomer was left within the shortcured Lucitone 199 and Accelar 20 resin specimens after processing and, because of this remaining monomer, water uptake (thus expansion of the specimen) was affected. Further studies should be completed regarding the presence and/or amount of this residual monomer. The Lucitone 199 short-cured resin specimens continued to expand from 60 to 90 days. This is another phenomenon that should be investigated to determine at what time period expansion would cease. The resin that stayed closest to its processed dimension after water storage was Lucitone 199 long-cured. Although this resin did not exhibit the least dimensional shrinkage during processing, it differed from Accelar 20 resin by only 0.059%. Lucitone 199 short-cured resin behaved in the least stable manner dimensionally during storage in water for 90 days.







Since no significant differences in shrinkage were noted between the resin groups after processing, on insertion, dentures made from these materials would probably not show any differences in fit. Even smaller linear dimensional changes occurred after storage in water. These changes are of a degree that would not be detected clinically after a period of wear comparable to the water storage periods. CONCLUSIONS No significant differences in linear dimension were found between any of the four resins due to processing or storage in water up to 90 days. The changes that occurred were so small that they would not be clinically detectable. REFERENCES 1. Sweeney WT. Denture base material: acrylic resins. J Am Dent Assoc 1939;26:1863-73. 2. Sweeney WT, Paffenbarger GC, Beall JR. Acrylic resins for dentures. J Am Dent Assoc 1942;29:7-33. 3. Woelfel JB, Ptienbarger GC, Sweeney WT. Changes in dentures during storage in water and in service. J Am Dent Assoc 1961;62:643-57. 4. Skinner EW, Cooper EN. Physical properties of denture resins. Part 1. Curing shrinkage and water sorption. J Am Dent Assoc 1943;30:184552. 5. Sweeney WT. Acrylic resins for prosthetic dentistry. Dent Clin North Am 1958;2:593-602. 6. Mowery WE, Burns CL, Dickson G, Sweeney WT. Dimensional stability of denture base resins. J Am Dent Assoc 1958;57:345-53. Reprint requests to: DR. DONNAL.DIXON COLLEGE OFDENTISTRY UNIVERSITY OF IOWA IOWA CITY,IA 52242




Linear dimensional variability of three denture base resins after processing and in water storage.

It has been shown that denture base resins shrink during curing and expand during storage in water. This investigation measured and compared linear di...
2MB Sizes 0 Downloads 0 Views