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Dimensional accuracy of improved dental stone and epoxy resin die materials. Part II: Complete arch form
Dimensional accuracy of improved dental stone and epoxy resin die materials. Part I1: Complete arch form N. R. Chaffee, DDS, MS, a I. H. Bailey, DDS, h and D. I. Sherrard, BS c
University of Nebraska Medical Center College of Dentistry, Lincoln, Neb. Statement o f p r o b l e m . Little information has been reported with regard to the dimensional accuracy of improved dental stone materials for reproduction of an entire arch form. P u r p o s e . The purpose of this study was to evaluate the ability of an epoxy resin die material and a type IV dental stone to dimensionally reproduce an entire arch form. M a t e r i a l and methods. Models were fabricated and measurements were made of reference marks to calculate dimensions from first molar to the midline bilaterally and between first molars. Each measurement was repeated three times and the mean measurement and percent relative change was calculated for each dimension. Results. The results revealed that the difference in the relative change in two dimensions was statistically significant for the epoxy resin group (p <0.05). Conclusions. The materials provided a similar degree of dimensional accuracy in reproducing a complete arch when used with addition silicone impression material. (J Prosthet Dent 1997;77:235-8.)
I m p r o v e d dental stone has been the m o s t popular material in dentistry for p r o d u c i n g dies with the lostwax technique. 14 To overcome the disadvantages o f improved dental stone, new materials have been introduced and are r e p o r t e d by the manufacturers to be dimensionally accurate, more abrasion resistant, and stronger than the improved stones. Whereas m a n y o f these materials have been previously c o m p a r e d with gypsum, the physical properties o f epoxy resin have been shown to be d e p e n d e n t on the material tested. 5-9 Commercial dental laboratories have used these new materials in the fabrication o f all-porcelain labial margin restorations and all-ceramic restorations. Little has been reported in the dental literature with regard to the dimensional accuracy o f these new materials for reproduction o f a single unit or for an entire arch form. In the first part o f this study, 1° the accuracy o f a type IV dental stone and epoxy resin die material to dimensionally reproduce a custom-fabricated metal die representing a single t o o t h was examined. The results o f the first part o f the study demonstrated that the epoxy resin die system (Ivoclar Epoxy Resin Die Material, IvoclarWilliams-Vivadent, Amherst, N. Y.) was an acceptable alternative to improved dental stone for a single unit die with respect to dimensional accuracy.I° aAssistant Professor, Department of Adult Restorative Dentistry. UPrivate Practice, Salt Lake City, Utah. CFourth year dental student, College of Dentistry, The Ohio State University, Columbus, Ohio. MARCH 1997
The purpose o f the second part o f this study was to evaluate and compare the accuracy o f an epoxy resin die material and a type IV dental stone to dimensionally reproduce an entire arch form. METHODS
AND MATERIAL
Master model A mandibular metal arch form (Model 41-51, Columbia D e n t o f o r m Corp., L o n g Island City; N. Y.) was used as the master model. Three stainless steel rods were machined on four sides to produce a point reference mark. The machined reference marks were then attached to the master arch form with cyanoacrylate (Zapit, Dental Ventures o f America, Inc., Anaheim Hills, Calif.) to provide points for measurement. The reference marks (Fig. 1 ) were located as follows: reference mark 1 at the embrasure between the central incisors; reference mark 2 in the central fossa o f the left first molar; and reference mark 3 in the central fossa of the right first molar. A relief template was made for the fabrication o f each custom tray by adaptation o f two thicknesses o f Kerr No. 8 baseplate wax (Kerr/Sybron, Romulus, Mich.) to the master arch form with the reference marks. Twenty custom trays were fabricated with 0.015-inch extra heavy weight tray material (Buffalo Manufacturing Co., Inc., Brooklyn, N. Y.) on an U l t r a - F o r m vacuum-forlning machine ( U l t r a D e n t Products, Inc., Salt Lake City, Utah). A custom base was made with type I V dental stone to allow orientation o f the master THE JOURNAL OF PROSTHETIC DENTISTRY
235
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Metal master model with three reference marks.
CHAFFEE, BAILEY, AND SHERRARD
WhipMix Corp., Louisville, Ky.) was mixed, with the m a n u f a c t u r e r ' s r e c o m m e n d e d w a t e r : p o w d e r ratio (23 m l / 1 0 0 gm) u n d e r a vacuum o f 710 m m H g (28 inches o f H g ) for a 60-second spatulation period. The stone was vibrated into the impression and allowed to set for 1 hour at ambient r o o m temperature and humidity before removal from the impression. The gypsum casts were then measured. Group II. Epoxy resin casts (Ivoclar, Ivoclar-Williams Vivadent) were fabricated from an impression, as done in group I. The casts were made individually and in accordance with the manufacturer's recommendations. Impressions were prepared with a coat o f isolating liquid followed by an application o f wetting powder. The epoxy material was combined with the activator at a ratio o f 15 m l / 2 . 5 ml and spatulated for 30 seconds. The resultant mixture was painted on the entire impression surface with a No. 1 sable brush and the remaining resin was poured into the impression. The material was allowed to cure for 3 hours at ambient room temperature (22.1 ° _+0.2 ° C) and humidity (60% _+10%) after which the arch form casts were recovered from the impressions for measurement. Measurement
Fig. 2. Polyvinyl siloxane impression of master mandibular arch form.
mandibular arch on a dental surveyor. The custom trays were aligned to the master arch form on the dental surveyor. Carbide bur shafts, placed in the vertical arm o f the dental surveyor to the custom trays, were attached with acrylic resin (Coe Tray Plastic, G.C. America, Inc., Chicago, Ill.). The alignment procedure was used to maintain the desired impression thickness while making the master impressions. Experimental groups
Group L Ten casts were made from individual impressions o f the master arch form. Type I high viscosity polyvinyl siloxane impression material was used to make the impressions in the trays and light body polyvinyl siloxane material (Reprosil, L. D. Caulk Co., Milford, Del.) was syringed onto the reference marks (Fig. 2). Impression material retention in the trays was obtained with the adhesive provided by the manufacturer. The impressions were allowed to polymerize at 37 ° C in 100% humidity. The master model was recovered from the impression, which was allowed to set for 1 hour at ambient r o o m temperature (22 ° _+0.2 ° C) and humidity (60% _+ 10%) before pouring. Improved dental stone (Silley Rock, 236
All casts were measured at x25 magnification using a microscope with a measuring accuracy o f 0.001 m m (model Smz, Nikon Inc., Garden City, N. Y.). The microscope was modified with an EPI illuminator, linear encoder state, and digital micrometer display (model 03L, Nikon Inc., Garden City, N.Y.). A direct light field was used with both systems. Each specimen was measured in an ordered sequence, namely dimension A, the distance between reference marks 1 and 2; dimension B, the distance between reference marks 1 and 3; and dimension C, the distance between reference marks 2 and 3 (Fig. 3). The measurements were repeated three times to determine the mean for each dimension. To aid in viewing the reference marks, graphite lines were scribed on the ridges o f the index pointer to aid in focusing at the reference point. All measurements were made by the same investigator. The measurements were made with the specimens at a m b i e n t r o o m t e m p e r a t u r e and h u m i d i t y (22.1 ° _+ 0.2 ° C and 60% _+ 10%). The mean for each dimension measured three times on the master arch form was used as the basis for determining the relative change in the respective dimension o f each sample according to the relationship: Dimension
i s~.~ic - D i m e n s i o n
i ~,~s~c~die
Percent relative change t =
Dimension
i ,~,~rdi,.
where i refers to the dimension (A, B, or C). These relative changes were then subjected to a repeated measures analysis o f variance (ANOVA) and subsequently VOLUME 77 NUMBER3
CHAFFEE, BAILEY, AND SHERRARD
THE JOURNAL OF PROSTHETIC DENTISTRY
0,10 •
I
0.01
°
i
N Epoxy
"Ore08
Gypsum -0.17 (9
I1)
n
-0.26
-0.35 Dimension A
Dimension B
Dimension C
Fig. 4. Relative change in dimension.
Table I. Statistical summaries of measurement values (ram)
Fig. 3. Illustration of master mandibular arch and dimensions measured. to Tukey comparisons to identify, for each dimension, any significant differences between the two groups in the relative changes. Student's t-test was used to test the relative changes o f each dimension in each group for significance from zero. M1 hypothesis testing was performed with an experiment-wise error level (alpha) o f 0.05. RESULTS The master arch form measured 35.412 _+0.024 mm, 34.342 +_ 0.029 mm, and 41.228 + 0.032 m m for dimensions A, B, and C, respectively. Summaries o f the measurement values and percent relative changes are presented in Table I, and the mean relative changes in each dimension are illustrated in Figure 4 for each group. The repeated measures ANOVA o f the percent relative changes demonstrates a significant difference in the relative change among the dimensions or locations studied (p = 0.0001) and a significant interaction between the groups and the dimensions or locations evaluated (p =
0.0065). The percent o f relative change for dimensions A and B for the epoxy resin material was significantly different from zero. A highly significant interaction was observed for the dimension measured and the type o f material. The location o f the measurement affected the relative change in dimension from the master model differently for each material.
DISCUSSION The results o f this study demonstrated differences in the relative change that were dependent on the location o f the measurement and the material. The difference in the relative change in dimensions A and B was statistically significant for the epoxy resin group whereas it was M A R C H 1997
and percent relative changes for the epoxy resin and stone die groups Group model Epoxy resin
Stone
N
10
10
Dimension
Measurement value
% Relative change
A
35.396 4- 0.019
- 0 . 0 4 6 -+ 0.053
B
34.244 -+ 0.024
- 0 . 2 8 4 -+ 0.069
C
41.231 -+ 0.028
0.007 + 0.068
A
35.435 -+ 0.049
0.064 -+ 0.139
B
34.317 -+ 0.044
-0.073 + 0.129
C
41.2314-+0.055
0.007+0.013
not statistically significant for the improved dental stone. It is difficult to determine the source o f these differences. The controlled placement o f the impression tray on the master model standardized the effect o f the impression material thickness. One possible source could be the technique used to construct the specimens. The epoxy resin specimens were fabricated in a standardized fashion, with the epoxy resin material applied to the impression beginning with the teeth on the side o f dimension B. Once the material covered the surface o f the impression, the remaining material was poured into the impression beginning with the side o f dimension B. The improved dental stone specimens were also fabricated in a standardized fashion, following the manufacturer's recommendations, again filling the impression beginning with the teeth on the side o f dimension B. The magnitude o f the differences in the relative change in dimensions A and B for the epoxy resin material studied would not be clinically significant when used for the construction o f complete arch removable die master models. The difference for dimension A was -0.05% and for dimension B was -0.3%, which calculates to 17.2 pm and 100 pro, respectively. These differences should not create large inaccuracies in interabutment distances for fixed partial dentures (FPDs) within a quadrant or major occlusal errors when the complete arch models are mounted on an articulator. 4 Therefore, the results o f 237
THE JOURNAL OF PROSTHETIC DENTISTRY
this study indicated that both the gypsum and epoxy resin die materials evaluated will provide a similar degree o f dimensional accuracy in reproducing a complete arch when used with addition silicone impression materials. Further investigation is required to determine the source o f the dimensional differences for the materials and to detail reproduction, hardness, and abrasion resistance. CONCLUSIONS
From this study, the following conclusions were drawn. 1. The epoxy resin material produced models that were slightly undersized in the dimensions from the right first molar to the central incisors (-0.3%) and from the left first molar to the central incisors (-0.05%). 2. The improved dental stone produced models that were slightly oversized in the dimensions from left first molar to the central incisors (0.06%) but slightly undersized from the right first molar to the central incisors
(0.07%). 3. The gypsum and epoxy resin die materials provided a similar degree o f dimensional accuracy in reproducing a complete arch when used with addition silicone impression materials. 4. Additional research is needed to compare epoxy resin and improved dental stone materials for detail reproduction, hardness, and abrasion resistance.
CHAFFEE, BAILEY, A N D SHERRARD
REFERENCES I. Toreskog S, Phillips RW, Schnell RJ. Properties of die materials: a comparative study. J Prosthet Dent 1966;16:119-31. 2. Hollenback GM, Smith DD. A further investigation of the physical properties of hard gypsum. J Calif Dent Assoc 1976;43:221-7. 3. Gett[eman L, Ryge G. Accuracy of stone, metal and plastic die materials. J Calif Dent Assoc 1970;46:28-31. 4. Craig RG. Restorative dental materials. 9th edition. St Louis, MO: The CV Mosby Co, 1993. 5. Moser JB, Stone DG, Willoughby GM. Properties and characteristics of a resin die material. J Prosthet Dent 1975;34:297-304. 6. Vermilyea SG, Huget EF, Wiskoski J II. Evaluation of resin die materials. J Prosthet Dent 1979;42:304-7. 7. Nomura GT, Reisbick MH, Preston JD. An investigation of epoxy resin dies. J Prosthet Dent 1980;44:45-50. 8. Aiach D, Malone WI-, Sandrik J. Dimensional accuracy of epoxy resins and their compatibility with impression materials. J Prosthet Dent 1984;52:5004. 9. BaileyJH, DonovanTE, PrestonJD.Thedimensionalaccuracyofimproved dental stone, silverplated, and epoxy resin die materials. J Prosthet Dent 1988;59:307-10. 10. Chaffee NR, Bailey IH, Sherrard DJ. Dimensional accuracy of improved dental stone and epoxy resin die materials. Part h single die. ] Prosthet Dent 1997;77:131-5. Reprint requests to: DR. NANCYR. CHAFFEE DEPARTMENTOF RESTORATIVEDENTISTRY COLLEGEOF DENTISTRy UNIVERSITYOF NEBRASKAMEDICALCENTER 40TH AND HOLDREGESTS. LINCOLN, NE 68583-0740
Copyright © 1997 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/97/$5,00 + 0. 10/1/78264
We express our sincere appreciation to Dr. William Johnston for his statistical assistance and to L. D. Caulk Co., WhipMix Corporation, and Ivoclar-Wil[iams-Vivadentfor their product support.
B o u n d v o l u m e s available to subscribers
Bound volumes of TheJournal of Prosthetic Dentistry are available to subscribers (only) for the 1997 issues from the publisher at a cost of $76.00 ($89.00 international) for Vol. 77 (January-June) and Vol. 78 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Volumes 75 and 76 are also available. Payment must accompany all orders. Contact Mosby-Year Book, Inc., Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, USA; phone (800)453-4351, or (314)453-435I. Subscriptions m u s t be in force to qualify. B o u n d v o l u m e s are n o t available in place o f a regular J o u r n a l subscription.
238
VOLUME 77 NUMBER 3
University of Nebraska Medical Center College of Dentistry, Lincoln, Neb. Statement o f p r o b l e m . Little information has been reported with regard to the dimensional accuracy of improved dental stone materials for reproduction of an entire arch form. P u r p o s e . The purpose of this study was to evaluate the ability of an epoxy resin die material and a type IV dental stone to dimensionally reproduce an entire arch form. M a t e r i a l and methods. Models were fabricated and measurements were made of reference marks to calculate dimensions from first molar to the midline bilaterally and between first molars. Each measurement was repeated three times and the mean measurement and percent relative change was calculated for each dimension. Results. The results revealed that the difference in the relative change in two dimensions was statistically significant for the epoxy resin group (p <0.05). Conclusions. The materials provided a similar degree of dimensional accuracy in reproducing a complete arch when used with addition silicone impression material. (J Prosthet Dent 1997;77:235-8.)
I m p r o v e d dental stone has been the m o s t popular material in dentistry for p r o d u c i n g dies with the lostwax technique. 14 To overcome the disadvantages o f improved dental stone, new materials have been introduced and are r e p o r t e d by the manufacturers to be dimensionally accurate, more abrasion resistant, and stronger than the improved stones. Whereas m a n y o f these materials have been previously c o m p a r e d with gypsum, the physical properties o f epoxy resin have been shown to be d e p e n d e n t on the material tested. 5-9 Commercial dental laboratories have used these new materials in the fabrication o f all-porcelain labial margin restorations and all-ceramic restorations. Little has been reported in the dental literature with regard to the dimensional accuracy o f these new materials for reproduction o f a single unit or for an entire arch form. In the first part o f this study, 1° the accuracy o f a type IV dental stone and epoxy resin die material to dimensionally reproduce a custom-fabricated metal die representing a single t o o t h was examined. The results o f the first part o f the study demonstrated that the epoxy resin die system (Ivoclar Epoxy Resin Die Material, IvoclarWilliams-Vivadent, Amherst, N. Y.) was an acceptable alternative to improved dental stone for a single unit die with respect to dimensional accuracy.I° aAssistant Professor, Department of Adult Restorative Dentistry. UPrivate Practice, Salt Lake City, Utah. CFourth year dental student, College of Dentistry, The Ohio State University, Columbus, Ohio. MARCH 1997
The purpose o f the second part o f this study was to evaluate and compare the accuracy o f an epoxy resin die material and a type IV dental stone to dimensionally reproduce an entire arch form. METHODS
AND MATERIAL
Master model A mandibular metal arch form (Model 41-51, Columbia D e n t o f o r m Corp., L o n g Island City; N. Y.) was used as the master model. Three stainless steel rods were machined on four sides to produce a point reference mark. The machined reference marks were then attached to the master arch form with cyanoacrylate (Zapit, Dental Ventures o f America, Inc., Anaheim Hills, Calif.) to provide points for measurement. The reference marks (Fig. 1 ) were located as follows: reference mark 1 at the embrasure between the central incisors; reference mark 2 in the central fossa o f the left first molar; and reference mark 3 in the central fossa of the right first molar. A relief template was made for the fabrication o f each custom tray by adaptation o f two thicknesses o f Kerr No. 8 baseplate wax (Kerr/Sybron, Romulus, Mich.) to the master arch form with the reference marks. Twenty custom trays were fabricated with 0.015-inch extra heavy weight tray material (Buffalo Manufacturing Co., Inc., Brooklyn, N. Y.) on an U l t r a - F o r m vacuum-forlning machine ( U l t r a D e n t Products, Inc., Salt Lake City, Utah). A custom base was made with type I V dental stone to allow orientation o f the master THE JOURNAL OF PROSTHETIC DENTISTRY
235
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Metal master model with three reference marks.
CHAFFEE, BAILEY, AND SHERRARD
WhipMix Corp., Louisville, Ky.) was mixed, with the m a n u f a c t u r e r ' s r e c o m m e n d e d w a t e r : p o w d e r ratio (23 m l / 1 0 0 gm) u n d e r a vacuum o f 710 m m H g (28 inches o f H g ) for a 60-second spatulation period. The stone was vibrated into the impression and allowed to set for 1 hour at ambient r o o m temperature and humidity before removal from the impression. The gypsum casts were then measured. Group II. Epoxy resin casts (Ivoclar, Ivoclar-Williams Vivadent) were fabricated from an impression, as done in group I. The casts were made individually and in accordance with the manufacturer's recommendations. Impressions were prepared with a coat o f isolating liquid followed by an application o f wetting powder. The epoxy material was combined with the activator at a ratio o f 15 m l / 2 . 5 ml and spatulated for 30 seconds. The resultant mixture was painted on the entire impression surface with a No. 1 sable brush and the remaining resin was poured into the impression. The material was allowed to cure for 3 hours at ambient room temperature (22.1 ° _+0.2 ° C) and humidity (60% _+10%) after which the arch form casts were recovered from the impressions for measurement. Measurement
Fig. 2. Polyvinyl siloxane impression of master mandibular arch form.
mandibular arch on a dental surveyor. The custom trays were aligned to the master arch form on the dental surveyor. Carbide bur shafts, placed in the vertical arm o f the dental surveyor to the custom trays, were attached with acrylic resin (Coe Tray Plastic, G.C. America, Inc., Chicago, Ill.). The alignment procedure was used to maintain the desired impression thickness while making the master impressions. Experimental groups
Group L Ten casts were made from individual impressions o f the master arch form. Type I high viscosity polyvinyl siloxane impression material was used to make the impressions in the trays and light body polyvinyl siloxane material (Reprosil, L. D. Caulk Co., Milford, Del.) was syringed onto the reference marks (Fig. 2). Impression material retention in the trays was obtained with the adhesive provided by the manufacturer. The impressions were allowed to polymerize at 37 ° C in 100% humidity. The master model was recovered from the impression, which was allowed to set for 1 hour at ambient r o o m temperature (22 ° _+0.2 ° C) and humidity (60% _+ 10%) before pouring. Improved dental stone (Silley Rock, 236
All casts were measured at x25 magnification using a microscope with a measuring accuracy o f 0.001 m m (model Smz, Nikon Inc., Garden City, N. Y.). The microscope was modified with an EPI illuminator, linear encoder state, and digital micrometer display (model 03L, Nikon Inc., Garden City, N.Y.). A direct light field was used with both systems. Each specimen was measured in an ordered sequence, namely dimension A, the distance between reference marks 1 and 2; dimension B, the distance between reference marks 1 and 3; and dimension C, the distance between reference marks 2 and 3 (Fig. 3). The measurements were repeated three times to determine the mean for each dimension. To aid in viewing the reference marks, graphite lines were scribed on the ridges o f the index pointer to aid in focusing at the reference point. All measurements were made by the same investigator. The measurements were made with the specimens at a m b i e n t r o o m t e m p e r a t u r e and h u m i d i t y (22.1 ° _+ 0.2 ° C and 60% _+ 10%). The mean for each dimension measured three times on the master arch form was used as the basis for determining the relative change in the respective dimension o f each sample according to the relationship: Dimension
i s~.~ic - D i m e n s i o n
i ~,~s~c~die
Percent relative change t =
Dimension
i ,~,~rdi,.
where i refers to the dimension (A, B, or C). These relative changes were then subjected to a repeated measures analysis o f variance (ANOVA) and subsequently VOLUME 77 NUMBER3
CHAFFEE, BAILEY, AND SHERRARD
THE JOURNAL OF PROSTHETIC DENTISTRY
0,10 •
I
0.01
°
i
N Epoxy
"Ore08
Gypsum -0.17 (9
I1)
n
-0.26
-0.35 Dimension A
Dimension B
Dimension C
Fig. 4. Relative change in dimension.
Table I. Statistical summaries of measurement values (ram)
Fig. 3. Illustration of master mandibular arch and dimensions measured. to Tukey comparisons to identify, for each dimension, any significant differences between the two groups in the relative changes. Student's t-test was used to test the relative changes o f each dimension in each group for significance from zero. M1 hypothesis testing was performed with an experiment-wise error level (alpha) o f 0.05. RESULTS The master arch form measured 35.412 _+0.024 mm, 34.342 +_ 0.029 mm, and 41.228 + 0.032 m m for dimensions A, B, and C, respectively. Summaries o f the measurement values and percent relative changes are presented in Table I, and the mean relative changes in each dimension are illustrated in Figure 4 for each group. The repeated measures ANOVA o f the percent relative changes demonstrates a significant difference in the relative change among the dimensions or locations studied (p = 0.0001) and a significant interaction between the groups and the dimensions or locations evaluated (p =
0.0065). The percent o f relative change for dimensions A and B for the epoxy resin material was significantly different from zero. A highly significant interaction was observed for the dimension measured and the type o f material. The location o f the measurement affected the relative change in dimension from the master model differently for each material.
DISCUSSION The results o f this study demonstrated differences in the relative change that were dependent on the location o f the measurement and the material. The difference in the relative change in dimensions A and B was statistically significant for the epoxy resin group whereas it was M A R C H 1997
and percent relative changes for the epoxy resin and stone die groups Group model Epoxy resin
Stone
N
10
10
Dimension
Measurement value
% Relative change
A
35.396 4- 0.019
- 0 . 0 4 6 -+ 0.053
B
34.244 -+ 0.024
- 0 . 2 8 4 -+ 0.069
C
41.231 -+ 0.028
0.007 + 0.068
A
35.435 -+ 0.049
0.064 -+ 0.139
B
34.317 -+ 0.044
-0.073 + 0.129
C
41.2314-+0.055
0.007+0.013
not statistically significant for the improved dental stone. It is difficult to determine the source o f these differences. The controlled placement o f the impression tray on the master model standardized the effect o f the impression material thickness. One possible source could be the technique used to construct the specimens. The epoxy resin specimens were fabricated in a standardized fashion, with the epoxy resin material applied to the impression beginning with the teeth on the side o f dimension B. Once the material covered the surface o f the impression, the remaining material was poured into the impression beginning with the side o f dimension B. The improved dental stone specimens were also fabricated in a standardized fashion, following the manufacturer's recommendations, again filling the impression beginning with the teeth on the side o f dimension B. The magnitude o f the differences in the relative change in dimensions A and B for the epoxy resin material studied would not be clinically significant when used for the construction o f complete arch removable die master models. The difference for dimension A was -0.05% and for dimension B was -0.3%, which calculates to 17.2 pm and 100 pro, respectively. These differences should not create large inaccuracies in interabutment distances for fixed partial dentures (FPDs) within a quadrant or major occlusal errors when the complete arch models are mounted on an articulator. 4 Therefore, the results o f 237
THE JOURNAL OF PROSTHETIC DENTISTRY
this study indicated that both the gypsum and epoxy resin die materials evaluated will provide a similar degree o f dimensional accuracy in reproducing a complete arch when used with addition silicone impression materials. Further investigation is required to determine the source o f the dimensional differences for the materials and to detail reproduction, hardness, and abrasion resistance. CONCLUSIONS
From this study, the following conclusions were drawn. 1. The epoxy resin material produced models that were slightly undersized in the dimensions from the right first molar to the central incisors (-0.3%) and from the left first molar to the central incisors (-0.05%). 2. The improved dental stone produced models that were slightly oversized in the dimensions from left first molar to the central incisors (0.06%) but slightly undersized from the right first molar to the central incisors
(0.07%). 3. The gypsum and epoxy resin die materials provided a similar degree o f dimensional accuracy in reproducing a complete arch when used with addition silicone impression materials. 4. Additional research is needed to compare epoxy resin and improved dental stone materials for detail reproduction, hardness, and abrasion resistance.
CHAFFEE, BAILEY, A N D SHERRARD
REFERENCES I. Toreskog S, Phillips RW, Schnell RJ. Properties of die materials: a comparative study. J Prosthet Dent 1966;16:119-31. 2. Hollenback GM, Smith DD. A further investigation of the physical properties of hard gypsum. J Calif Dent Assoc 1976;43:221-7. 3. Gett[eman L, Ryge G. Accuracy of stone, metal and plastic die materials. J Calif Dent Assoc 1970;46:28-31. 4. Craig RG. Restorative dental materials. 9th edition. St Louis, MO: The CV Mosby Co, 1993. 5. Moser JB, Stone DG, Willoughby GM. Properties and characteristics of a resin die material. J Prosthet Dent 1975;34:297-304. 6. Vermilyea SG, Huget EF, Wiskoski J II. Evaluation of resin die materials. J Prosthet Dent 1979;42:304-7. 7. Nomura GT, Reisbick MH, Preston JD. An investigation of epoxy resin dies. J Prosthet Dent 1980;44:45-50. 8. Aiach D, Malone WI-, Sandrik J. Dimensional accuracy of epoxy resins and their compatibility with impression materials. J Prosthet Dent 1984;52:5004. 9. BaileyJH, DonovanTE, PrestonJD.Thedimensionalaccuracyofimproved dental stone, silverplated, and epoxy resin die materials. J Prosthet Dent 1988;59:307-10. 10. Chaffee NR, Bailey IH, Sherrard DJ. Dimensional accuracy of improved dental stone and epoxy resin die materials. Part h single die. ] Prosthet Dent 1997;77:131-5. Reprint requests to: DR. NANCYR. CHAFFEE DEPARTMENTOF RESTORATIVEDENTISTRY COLLEGEOF DENTISTRy UNIVERSITYOF NEBRASKAMEDICALCENTER 40TH AND HOLDREGESTS. LINCOLN, NE 68583-0740
Copyright © 1997 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/97/$5,00 + 0. 10/1/78264
We express our sincere appreciation to Dr. William Johnston for his statistical assistance and to L. D. Caulk Co., WhipMix Corporation, and Ivoclar-Wil[iams-Vivadentfor their product support.
B o u n d v o l u m e s available to subscribers
Bound volumes of TheJournal of Prosthetic Dentistry are available to subscribers (only) for the 1997 issues from the publisher at a cost of $76.00 ($89.00 international) for Vol. 77 (January-June) and Vol. 78 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Volumes 75 and 76 are also available. Payment must accompany all orders. Contact Mosby-Year Book, Inc., Subscription Services, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, USA; phone (800)453-4351, or (314)453-435I. Subscriptions m u s t be in force to qualify. B o u n d v o l u m e s are n o t available in place o f a regular J o u r n a l subscription.
238
VOLUME 77 NUMBER 3