STATEMENT OF PROBLEM: Die materials require abrasion resistance, dimensional stability with time, and high surface wettability for adequate material properties. Wear of gypsum materials is a significant problem in the fabrication of accurately fitting cast prosthetic devices. So It has been recommended that the use of die hardener before carving or burnishing ofthe wax pattern. PURPOSE: The purpose of this study was to compare the abrasion resistance and surface microhardness(Knoop) with 3 commonly used gypsum die materials(MG Crystal Rock, Super plumstone, GC FUJIROCK(R) EP) with and without the application of 2 die hardeners. MATERIAL AND METHODS: Three die materials were evaluated for abrasion resistance and surface microhardness after application of 2 die hardeners(Die hardener and Stone die & plaster hardener). Thirty specimens of each gypsum material were fabricated using an impression of resin die(Pattern resin; GC Corporation, Japan) with 1-mm high ridges, sloped 90 degrees. Gypsum materials were mixed according to manufacturer's recommendations and allowed to set 24 hours before coating. Specimens were arbitrary assigned to 1 of 3 treatment subgroups (n=10/subgroup): no treatment(control), coated with Die hardener, and coated with Stone die & plaster hardener. Abrasion resistance(measured by weight loss) was evaluated using device in 50g mass perpendicular to the ridges. Knoop hardness was determined by loading each specimen face 5 times for 15 seconds with a force of 50g. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Conclusions: The obtained results were as follows: 1. 3 types of die stone evaluated in this study did not show significant differences in surface hardness and abrasive resistance(P<.05). 2. In the abrasive resistance test, there were no significant differences between GC FUJIROCK(R) EP and MG Crystal Rock with or without 2 die hardener(P<.05). 3. Super plumstone treated with Stone die & plaster hardener showed increased wear loss(P<.05). 4. Die hardener coatings used in this study decreased the surface hardness of the gypsum material(P<.05).
Calcium Sulfate* ; Hardness ; Wettability

PURPOSE: The purpose of this study was to verify the effect of the abutment superimposition process on the final virtual model in the scanning process of single and 3-units bridge model using a dental model scanner. MATERIALS AND METHODS: A gypsum model for single and 3-unit bridges was manufactured for evaluating. And working casts with removable dies were made using Pindex system. A dental model scanner (3Shape E1 scanner) was used to obtain CAD reference model (CRM) and CAD test model (CTM). The CRM was scanned without removing after dividing the abutments in the working cast. Then, CTM was scanned with separated from the divided abutments and superimposed on the CRM (n=20). Finally, three-dimensional analysis software (Geomagic control X) was used to analyze the root mean square (RMS) and Mann-Whitney U test was used for statistical analysis (α=.05). RESULTS: The RMS mean abutment for single full crown preparation was 10.93 µm and the RMS average abutment for 3 unit bridge preparation was 6.9 µm. The RMS mean of the two groups showed statistically significant differences (P<.001). In addition, errors of positive and negative of two groups averaged 9.83 µm, −6.79 µm and 3-units bridge abutment 6.22 µm, −3.3 µm, respectively. The mean values of the errors of positive and negative of two groups were all statistically significantly lower in 3-unit bridge abutments (P<.001). CONCLUSION: Although the number of abutments increased during the scan process of the working cast with removable dies, the error due to the superimposition of abutments did not increase. There was also a significantly higher error in single abutments, but within the range of clinically acceptable scan accuracy.
Calcium Sulfate ; Crowns ; Dental Models

No abstract available.
Acute Kidney Injury ; Calcium Sulfate ; Calcium ; Hypercalcemia

No abstract available.
Animals ; Calcium Sulfate* ; Dogs* ; Humans* ; Regeneration*

In process of fabrication of a fixed partial denture, dies are trimmed to expose margins of the preparations. The need for the soft tissue cast is quite evident as the soft tissue emergence profile that surrounds the prepared tooth is destroyed in the process of fabrication. This article describes a modified technique to fabricate the soft tissue cast for the conventional fixed partial denture. The impression made with the polyvinylsiloxane was first poured to prepare the die cast. After retrieval of the cast, the same impression was poured second time with the resin based resilient material to cover the facial and proximal gingival areas. The remaining portion of the impression was poured with the gypsum material. This technique does not require additional clinical appointment, second impression procedure, technique sensitive manipulations with impression, or cumbersome laboratory procedures. The simplicity of this technique facilitates and justifies its routine use in fabrication of the fixed partial denture.
Calcium Sulfate ; Denture, Partial, Fixed ; Tooth

OBJECTIVETo explore a simple but novel method of strengthening gypsum material by cyanoacrylate infiltration. To evaluate the influence of cyanoacrylate on the mechanical properties of dental gypsum models.

METHODSGypsum specimens were polished to the dimension of 35 mmx4 mmx4 mm. Butyl-cyanoacrylate was diluted with chloroform at different concentrations, namely 20% and 30% cyanoacrylate. Gypsum specimens were infiltrated by diluting one component of cyanoacrylate at different concentrations for 8 h and then dried for analysis. The changes in elastic modulus, fracture toughness, compressive strength, biaxial strength, brinell hardness were measured. The data were analyzed using software OriginPro 8.

RESULTSThe viscosity measurements indicated that diluted cyanoacrylate were Newtonian fluids and the viscosity increased slightly within the 48 hours of preparation but still similar as water at room temperature, which could be used to infiltrating gypsum. The gypsum infiltrated with cyanoacrylate exhibited good physicochemical properties. The biaxial strength, fracture toughness, compressive strength and brinell hardness of the gypsum were improved by 39%, 30%, 63% and 18%, respectively.

CONCLUSIONCyanoacrylate can significantly improve the strength of gypsum model which indicates the potential clinical application.

Animals ; Calcium Sulfate ; Osteogenesis ; Periosteum ; Rats ; Skull

This essay is to present an improvement on the concentration assay for hemihydrate gypsum in plaster of Paris bandage-Viscose form.
Calcium Sulfate ; analysis ; Casts, Surgical ; Titrimetry ; methods

PURPOSE: If bone grafts and guided tissue regeneration are effective individually in treating osseous defects, then the question is, what would happen when they are combined. Bone grafts using Calcium Carbonate(Biocoral) and Guided Tissue Regeneration using Calcium Sulfate(CALMATRIX) will maximize their advantages and show the best clinical results in intrabony defects. This study was to compare the effects of a combination of CS and CC with control treated only with modified widman flap in a periodontal repair of intrabony defects. MATERIALS AND METHODS: 30 patients with chronic periodontitis were used in this study. 10 patients were treated with a combination of CS and CC as the experimental groupII and another 10 patients were treated with CC as the experimental groupI, and the remaining 10 patients, the control group were treated only with modified widman flap. Clinical parameters including probing depth, gingival recession, bone probing depth and loss of attachment were recorded 6 months later. RESULTS: The probing depth changes were 3.30+/-1.34 mm in the control group, 4.2+/-1.55 mm in the experimental groupI(CC) and 5.00+/-1.33 mm in the experimental groupII(CS+CC). They all showed a significant decrease 6 months after surgery(p <0.01). There was a significant difference(p <0.05) between the control and experimental group. However there were no significant difference(p <0.05) between the experimental groupIand II. The gingival recession changes w -1.30+/-1.25 mm in the control group, This is a significant difference(p <0.01). However, there was a -0.50+/-0.53 mm change in the experimental groupI(CC) and -0.60+/-0.97 mm in the experimental groupII(CS+CC). In addition, in terms of gingival recession, there was a no significance difference(p <0.05) among the groups. The clinical attachment level changes were 2.00+/-1.33 mm in the control group, 3.60+/-1.58 mm in the experimental groupI(CC) and 4.40+/-1.17 mm in the experimental groupII(CS+CC). They all showed a significant decrease 6 months after surgery(p <0.01). There was a significant difference(p <0.05) between the control and experimental group. However there was a no significance difference(p <0.05) between the experimental groupI andII. The bone probing depth changes were 0.60+/-0.52 mm in the control group, 3.20+/-1.48 mm in the experimental groupI (CC) and 4.60+/-1.43 mm in the experimental groupII(CS+CC). All of them showed a significant decrease 6 months after surgery(p <0.01), there was a significance difference(p <0.05) among the groups. CONCLUSION: Treatment using a combination of CS and CC have a potential to improve periodontal parameters in intrabony defects and More efficient clinical results can be expected in intrabony defects less than 2 walls grafted with CS and CC.
Calcium ; Calcium Carbonate ; Calcium Sulfate ; Chronic Periodontitis ; Gingival Recession ; Guided Tissue Regeneration ; Humans ; Transplants

PURPOSE: The accuracy of a gypsum model (GM), which was taken using a conventional silicone impression technique, was compared with that of a polyurethane model (PM), which was taken using an iTero(TM) digital impression system. MATERIALS AND METHODS: The maxillary first molar artificial tooth was selected as the reference tooth. The GMs were fabricated through a silicone impression of a reference tooth, and PMs were fabricated by a digital impression (n=9, in each group). The reference tooth and experimental models were scanned using a 3 shape convince(TM) scan system. Each GM and PM image was superimposed on the registered reference model (RM) and 2D images were obtained. The discrepancies of the points registered on the superimposed images were measured and defined as GM-RM group and PM-RM group. Statistical analysis was performed using a Student's T-test (alpha=0.05). RESULTS: A comparison of the absolute value of the discrepancy revealed a significant difference between the two groups only at the occlusal surface. The GM group showed a smaller mean discrepancy than the PM group. Significant differences in the GM-RM group and PM-RM group were observed in the margins (point a and f), mesial mid-axial wall (point b) and occlusal surfaces (point c and d). CONCLUSION: Under the conditions examined, the digitally fabricated polyurethane model showed a tendency for a reduced size in the margin than the reference tooth. The conventional gypsum model showed a smaller discrepancy on the occlusal surface than the polyurethane model.
Calcium Sulfate* ; Models, Theoretical ; Molar ; Polyurethanes* ; Silicones ; Tooth ; Tooth, Artificial