of new denture
G. H. Latta, Jr., D.D.S., M.S.,* W. F. Bowles, J. E. Conkin, B.P.S., M.S.***
Ten maxillary dentures were constructed on standard-sized casts in each of four acrylic resins. Uniform placement of the artificial teeth and thickness of the base were maintained by use of a silicone rubber mold. Metal shot was luted in preselected positions to the dentures and the land of the cast. Frontal, lateral, and occlusal radiographs were made of the dentures at time intervals of (1) before processing, (2) after processing, (3) immediately after removal from the cast, and (4) 30 days later. Study of the radiographs revealed significant variations in position of the metal shot from the before-processing baseline within each group of dentures and significant differences between groups of dentures. (J PROSTEET DENT 1990;63:654-61.)
crylic resins have been advocated for use as denture base materials for many years, and evaluation of their physical and chemical characteristics has been extensive.lM8Recent developments in dental products and methods of polymerization have led to marketing of purportedly superior resins for use in removable prosthodontics. The study of these new products is limited, however, and does not include observation of denture base stability in three dimensions.s-14 Investigators have shown that the density change that occurs during polymerization of methylmethacrylate results in a linear shrinkage calculated to be 0.2% to 0.5%.*51 l6 This shrinkage is compensated somewhat by expansion due to water sorption so that the final denture base approaches its original size and thereby its clinical acceptability.‘> l7 This study was determined the three-dimensional stability of several complete denture base resin systems after polymerization.
METHODS Forty maxillary dentures were constructed on duplicate casts obtained from a silicone rubber mold (Figs. 1 and 2). To obtain an orientation device for standardization of denture fabrication, an additional silicone mold was made of a wax maxillary denture on one of the duplicate casts and
*Associate **Associate tics. ***Associate
Professor, Professor Professor,
Department of Prosthodontics. and Chairman, Department Department
Fig. 1. Standard cast. attached to a squared stone base (Fig. 3). Uniform placement of the artificial teeth for the test dentures was accomplished by first placing them in this mold, flowing warm wax over the collars of the teeth, and fully seating a duplicate cast in the mold. The palate of the denture bases was maintained at one thickness of baseplate wax. Prior to processing, metal shot was luted into the artificial teeth, the denture base, and the cast land area by spot curing it with autopolymerizing acrylic resin in preselected positions (Fig. 4). Although an attempt was made to place the metal shot in approximately the same location for each test denture, no measurement would be made except within each denture itself and therefore exact location was irrelevant. Ten dentures were made in each of the selected
Fig. 2. Maxillary denture. Fig. 3. Silicone mold for uniform placement of teeth, thickness of denture base, and orientation of radiographs.
Fig. 4. Reference points of metal shot in artificial teeth, denture base, and cast land area.
denture base resins (Table I). Polymerization of the denture base resin system was carried to completion by accepted techniques,ls and according to manufacturer’s instructions. The dentures were replaced in the silicone rubber mold to orient them for frontal, lateral, and occlusal radiographs at time intervals of (1) before processing, (2) after processing, (3) immediately following removal from the cast, and (4) after 30 days (Fig. 5). Uniform x-ray focal length in each dimension was maintained by use of an aiming device (bite wing indicator arm and aiming ring-XCP, Rinn Corp., Elgin, Ill.) fixed to the silicone mold device (Fig. 3). By rotating the squared mold and changing the aiming device to the
proper dimension, the frontal, lateral, and occlusal radiographs could be returned to exactly the same angulation and focal length at each interval. Measurement of positional changes of the metal shot within each denture base, and between the denture base and the land area of the cast was made by examination of the radiographs with a vernier caliper accurate to O.OOO5 inch (Sylvac Ultra-Cal II, F.V. Fowler Co. Inc., Newton, Mass.). The measurements were made to the outer perimeter of each metal shot, thereby eliminating the need for uniform dimension of the shot. A’-B’ was designated the cross-arch measurement, B’-C’ the diagonal measurement, and A-C the anteroposterior measurement. Statistical ccc
I. Test resins
6. Occlusal, frontal, and lateral radiographs.
significance was determined for spatial relationships by using sample means to compute one-factor ANOVAs. Significant F tests were further studied with Scheffe’s post hoc test.
RESULTS An average of measured relationships between radiographic images of the metal shot falling within 0.005 inches was accepted as the true value of the measurement. To maintain consistency, all measurements of the dentures within each resin system were made by the same investigator. Differences between the before-processing measurement and each of the later time-period measurements were obtained, and mean values for the 10 dentures in each group were calculated (Tables II and III). The pattern of change noted for the final measurements (after 30 days) was fairly consistent in all but one dimension, that is, primarily a shrinkage in the occlusal dimension, expansion in the frontal dimension, but divided between shrinkage and expansion in the lateral dimension (Fig. 6). In this regard, mean changes seen in the occlusal dimension were 0.016 inch or less except in two instances, whereas mean changes in the frontal and lateral dimensions were much greater, averaging 0.023 inch in the frontal dimension and 0.034 inch in the lateral. Considering the occlusal dimension by itself, most groups shrank in the cross arch (A’-B’) and expanded diagonally
Hy-Pro Lucitone denture base resin
The L.D. Caulk Company Division of Dentsply (compressionmolding) International, Inc. Milford, Del. PERform denture Whaledent International system’ (injection New York, N.Y. molding) SR-Ivocap denture Ivoclar (USA) Inc. system (injection San Marco, Calif. molding) Accelar 20 denture Modern Materials acrylic (compression Columbus Dental molding) St. Louis, MO.
(B’-C’) and anteroposteriorly (A’-C’) before removal from the cast. After removal from the cast, nearly all groups shrank in every direction. They showed little change after 30 days with the exception in groups 1 and 2 which shrank 0.010 inch anteroposteriorly and expanded 0.018 inch, making their final measurements close to the original. It was also noted that groups 3 and 4 had larger changes than either group 1 or 2 at their final measurements. However, in real numbers these changes were less than 0,011 inch in the cross arch, 0.047 inch diagonally, and 0.020 inch anteroposteriorly. As stated before, mean changes in the frontal and lateral dimensions were much greater than in the occlusal dimensions. The cross-arch changes before removal from the cast varied from 0.010 to 0.033 inch in the frontal dimension, and from 0.003 to 0.102 inch in the lateral dimension. Although the final (after 30 days) frontal cross-arch change for all groups was 0.015 inch or less, the lateral dimension change remained large, varying from 0.051 to 0.069 inch. In like manner, the anteroposterior change before removal from the cast varied from 0.028 to 0.061 inch in the frontal dimension and 0.008 to 0.036 inch in the lateral dimension. This change also decreased in the final (after 30 days) frontal dimension to 0.022 inch or less, but remained large in the lateral dimension up to 0.056 inch. Diagonal changes were similar to cross-arch and anteroposterior changes except that group 2 showed a frontal change of 0.122 inch, which was nearly double any other change observed. A review of the raw data showed that this remarkable change was consistent for all samples, 0.097 inch or more in eight of the 10 samples. Mean changes in the occlusal dimension for all groups fell below 1% except in two instances (Fig. 7). However, changes in the frontal and lateral dimensions were much greater, where only three measurements in the frontal dimension fell below 0.5%) whereas only two in the lateral dimension fell below 1% . The cross-arch (A’-B’) measure-
Mean values of positional changes of metal shot (inches) Group Measure*
Occlusal A’-B’ B’-C’ A’-%’ Frontal A’-B’ B’-C’ A’X Lateral A’-B’ B’-C’
A’-C’ 0cc1usal A’-B’ B’-C’ A’4 Frontal AI-B’ B’-C’ A’-C’ Lateral A’-B’ B’-C’ A’-C’ Occlusal A’-B’ B’-C’ A’42 Frontal A’-B’ B’-C’ A’-C’ Lateral A’-B’ B’-C’ A’-C’
cross-arch; B’-C’, diagonal; A’-C’, 3 before-removal data not available.
-0.006 0.004 0.005
-0.006 0.001 -0.002
-0.007 0.005 0.009
-0.021 0.015 -0.044
-0.010 -0.018 -0.028
-0.033 0.026 -0.061
0.033 -0.028 0.008
-0.003 -0.001 0.050
0.102 -0.041 0.033
-0.004 0.001 0.002
-0.006 0.001 -0.024
-0.011 -0.025 -0.018
-0.015 0.005 -0.029
-0.013 0.009 -0.015
0.018 -0.022 0.051
-0.019 0.045 -0.009
0.001 0.010 -0.009
0.016 -0.012 0.002
0.052 -0.015 0.048
-0.065 0.018 -0.049
0.061 -0.003 -0.001
-0.006 0.008 -0.008
-0.004 0.003 -0.006
-0.010 -0.039 -0.016
-0.013 -0.011 -0.026
0.015 -0.004 0.017
0.007 0.122 0.004
-0.015 0.046 0.022
0.049 -0.017 0.011
0.051 -0.022 0.056
-0.051 0.021 -0.052
0.059 -0.015 0.004
ments in the lateral dimension showed the greatest change, varying from 6% to 9%. Significant differences in mean dimensional change between the resin systems were studied at the after-30-days time period (Table IV). In the occlusal dimension, group 4 diered significantly in cross-arch change and group 3 differed in diagonal change. In the frontal dimension, groups 3 and 4 differed in cross-arch change and group 2 differed in diagonal change. Only in the lateral dimension were differences in anteroposterior change seen, where groups 2 and 3 showed significance. Group 3 differed in cross-arch and anteroposterior change in this dimension as well. Measurements between metal shot incorporated in the
land area of the cast and metal shot in the dentures could only be followed up to the point of the before-removal status, after which their relationship was lost. Investigation of these preliminary measurements revealed no unusual findings.
DISCUSSION Previous investigations performed in two dimensions demonstrated dimensional changes during the processing of denture base resin systems in the range of 0.2 % to 0.5 % . The results of this study closely duplicated those findings in the occlusal dimension, where mean changes were generally lessthan 1% . In contrast, much greater variation was
Range of positional changes after 30 days (inches) Mean Group
-0.006 0.008 -0.008
-0.004 0.003 -0.006
-0.010 -0.039 -0.016
-0.013 -0.011 -0.026
0.015 -0.004 0.017
0.007 0.122 0.004
-0.015 0.046 0.022
-0.002 0.020 -0.004
0.049 -0.017 0.011
0.051 -0.022 0.056
-0.051 0.021 -0.052
0.059 -0.015 -
0.005 0.016 0.014 0.005 0.014 0.033 0.005 0.012 0.027 0.006 0.014 0.018 0.007 0.011 OMl 0.016 0.030 0.058 0.008 0.019 0.029 0.008 0.016 0.022 0.020 0.010 0.008 0.021 0.011 0.018 0.016 0.025 0.019 0.016 0.007 0.009
0.002 0.027 0.022 0.003 0.025 0.036 0.001 -0.020 0.036 0.000 0.008 0.000 0.022 0.014 0.036 0.030 0.162 0.068 0.012 0.068 0.066 0.012 0.041 0.025 0.069 0.021 0.023 0.082 -0.010 0.087 -0.008 0.048 -0.034 0.078 -0.005 0.010
-0.014 -0.011 -0.019 -0.010 -0.017 -0.072 -0.018 -0.059 -0.060 -0.019 -0.037 -0.066 0.000 -0.014 0.008 0.018 0.068 -0.085 -0.027 0.010 -0.026 -0.013 -0.017 -0.040 0.004 -0.026 -0.001 0.025 -0.042 0.036 -0.101 -0.035 I -0.098 0.036 -0.029 -0.022
noted when the third dimension was added: mean changes were in the range.of 0.2% to 8.1% in the frontal dimension and 0.2% to 9% in the lateral. The greatest mean changes were seen in the lateral dimension where cross-arch measurements averaged 7.5 % . Caution should be used when putting great significance in this finding, however, because the before-processing crossarch measurements in this dimension averaged only 0.697 inch. A change of small but equal magnitude would be a 100% change and a minuscule 0.069 inch would represent a 10 % change! ln thii regard, these same measurements in the occlusal and frontal dimensions averaged only 0.4% and 0.8%) respectively. Similarly, the diagonal change in
the lateral dimension was only 1.4% and the anteroposterior was 1.6 % . ln assessing the superiority of the resin systems, group 3 showed statistically greater dimensional change in six measurements, groups 2 and 4 in two measurements, and group 1 did not prove statistically different in any measurement. It should also be noted that group 2 was slightly superior, although not significantly so, in the occlusal dimension when real numbers are considered. Group 2 did equally well in the frontal dimension for two of the three measurements, but surprisingly showed by far the greatest dimensional change in the diagonal measurement (B’-(Y), where there was considerable variation in all groups except
Fig. 6. Positional changes (inches) “after 30 days.”
one. Likewise, even though groups 3 and 4 were inferior in the cross-arch measurement in the frontal dimension, this difference was only 0.017 to 0.029 inch, respectively, probably not clinically significant. In the lateral dimension, group 3 showed the greatest variation by being directly opposite to all other groups, expanding when they shrank and shrinking when they expanded. This variation led to significant differences between group 3 and the other groups. However, the dimensional changes for all groups from the zero level were nearly equal, whether positive or negative. Only in one instance, the anteroposterior 0.001 inch measurement of group 4, did
any resin come within 0.010 inch of its original dimension. Thus, even though some statistically significant differences were seen, no resin system should be declared clearly superior in the lateral dimension.
The degree of dimensional change found in the resin systems studied indicates a continued need for procedures to correct the fit and function of complete dentures before their delivery to patients; that is, adjustment of pressure spots on the tissue surface and remounts to correct occlusal discrepancies are still required. Therefore, dentists must be
Fig. 7. Percent
Table IV. Statistical days
ANOVA F-test Cross-arch
Diagonal (B’-C’) Occlusal Frontal Lateral Anteroposterior Occlusal Frontal
Occlusal Frontal Lateral
changes after 30
13.263 65.728 20.975 60.255 14.313 (A’ -C ’ 1 1.325 1.089 87.019
post hoc test (significant
0.0015 0.0001 0.0001
0.0001 0.0001 0.0001
2, 3 3
0.2835 0.3682 0.0001 at 95%).
skeptical of claims of improved dimensional stability and quality of fit of dentures and continue to use accepted and proven prosthodontic techniques for patient treatment.
Standard-size casts were used to make 10 maxillary dentures in each of four different denture base resin systems. Uniform placement of artificial teeth and thickness of the base were maintained and metal shot was luted to the dentures in preselected positions. Occlusal, frontal, and lateral radiographs were made of the dentures at four time intervals and studied to determine differences in dimensional stability of the resin systems. 1. Changes in position of the metal shot incorporated within the dentures were noted in each of the occlusal, frontal, and lateral dimensions for all resin systems. 2. The pattern of positional change during polymerizaJUNE
tion was primarily a shrinkage in the occlusal dimension, expansion in the frontal dimension, and shrinkage and expansion alike in the lateral dimension. 3. The mean positional changes generally fell below 1% in the occlusal dimension but were much larger in the frontal and lateral dimensions, ranging from 0.2% to 8.1% frontally and 0.2 % to 9 % laterally. 4. Significant differences between resin systems were observed in mean positional changes in all three dimensions. REFERENCES 1. Skinner EW, Cooper EN. Physical properties of denture resins: Part 1. curing shrinkage and water sorption. J Am Dent Assoc 1943;30:1845-52. 2. Skinner EW. Acrylic denture base materials: their physical properties and manipulation. J PFKSTHET DENT 1951;1:161-7. 3. McCracken WL. An evaluation of activated methyl methacrylata denture base materials. J PROSTHET DENT 1952;2:68-83. 4. Kydd WL. Complete denture base deformation with varied occlusal tooth form. J PROSTHET DENT 1956;6:714-8. 5. Ryge G, Fairhurst CW. An evaluation of denture adaptation on the basis of contour meter readings. J PROSTHET DENT 1969;9:755-60. 6. Mirza FD. Dimensional stability of acrylic resin dentures. J PROSTHET DENT 1961;11:648-57.
7. Sorensen SE, Ryge F. Flow and recovery
An innovative Harold
Tel Aviv University, Aviv, Israel
8. Peyton FA, Anthony DH. Evaluation of dentures processed by different techniques. J PROSTH~-T DENT X%3$3:269-82. 9. Ogle RE, Lewis EA, Sorensen SE. A new visible light curing system applied to prosthodontics and orthodontics. Buffalo Dental Review 1985;1:1-4. 10. Schmidt KH.
SR-Ivocap system and denture structure. Quintessence Intl 1976;7:1-4. 11. Trage R. Experience grained with SR-Ivocap system. Quintessence Intl 1980;11:1-6.
12. Clinical Research Associates. Light-cure system for denture bases, repairs, and relines. CRA Newsletter 1986;lO:l. 13. Clinical Research Associates. Denture base construction system. CRA Newsletter 1988;12:11. 14. Arnold TG, Schulte JK, Anderson GC. Dimensional stability of injection and conventional processing of denture acrylic [Abstract]. J Dent Res 1987;66:125. 15. Woelfel JB, Paffenharger CC, Sweeney WT. Dimensional changes occurring in dentures during processing. J Am Dent Assoc 1960;61:413-30. 16. Phillips RW. Skinner’s science of dental materials. 8th ed. Philadelphia: WB Saunders Co, 1982;195-204. 17. Skinner EW, Jones PM. Dimensional stability of self-curing denture base acrylic resin. J Am Dent Assoc 1955;51:426-31. 18. Woelfel JB. Processing complete dentures. Dent Clin North Am 1977; 21:329-38. Reprint
DR. GEORGE H. LATTA, JR. UNIVEFWTY OF TENNESSEE, MEMPHIS COLLEGE OF DENTISTRY 875 UNION AVE. MEMPHIS, TN 38163
B.D.S., L.D.S., R.C.S.(Eng),*
and Mel Rosenberg,
hygiene Ph.D.** Tel
A simple and rapid test for measuring oral hygiene was recently developed. It is based on the rate of oxygen consumption of oral expectorates of milk. This investigation modified the test to study denture hygiene. The dentures of 20 patients were immersed in 10 mL of sterile milk. After a 2-minute agitation, 3 mL of milk was added to test tubes containing methylene blue. The time required for color change at the bottom of the test tube, which is indicative of the rate of oxygen consumption, was recorded. For comparison with visual plaque accumulation, the dentures were coated with disclosing solution and the extent of plaque was scored by three examiners. A correlation was found between the plaque index scores and results of the milk test (r = -0.64, p < 0.005). The data suggest the use of this test to monitor denture hygiene. (J PROSTHET DENT 1990;63:661-4.)
oft tissue changes associated with unclean removable dentures are denture stomatitis, inflammatory papillary hyperplasia, and chronic candidiasis.le6 Since most of the causative microorganisms in denture stomatitis reside
This study was carried out in the Alpha Omega Research tories, supported by the Alpha Omega Foundation. *Senior Lecturer, Department of Oral Rehabilitation. **Senior Lecturer, Laboratory of Oral Microbiology. 1011/18378 THEJOURNALOFPROSTHETICDENTISTRY
on the denture, disinfection of the denture is an essential preventative procedure.7-g The extent of plaque on dentures can be demonstrated by dye binding (disclosing) techniqueslO and assessment of specific organisms obtained by plating oral samples on selective growth media.9 Residual plaque accumulations after use of denture cleansers have been examined with a scanning electron microscope.lrf l2 Altman et al.13 critically evaluated methods to determine the cleanliness of dentures and suggest a spectrofluorometric protein assay of plaque as a most useful guide to denture cleanser efficacy. 661