• Journal of Powder Materials
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• v.13 no.5 s.58
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• pp.340-350
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• 2006

Nanostructured materials exhibit attractive mechanical properties that are often superior to the performance of their coarse-grained counterparts. However, one major drawback is their low ductility, which limits their potential applications. In this paper, different strategies to obtain both high strength and enhanced ductility in nanostructured materials are reported for Ti-base and Zr-base alloys. The first approach consists of designing an in-situ composite microstructure containing ductile bcc or hop dendrites that are homogeneously dispersed in a nanostructured matrix. The second approach is related to refining the eutectic structure of a Ti-Fe-Sn alloy. For all these materials, the microstructure, mechanical properties, deformation and fracture mechanisms will be discussed.

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.4
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• pp.232-243
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• 2021

Purpose: The purpose of this study was to evaluate the shear bond strength of various 3D printed denture base resins and the conventional denture base resin to various denture relining materials. Materials and Methods: For denture base materials, a heatcured (Vertex RS) and two types of 3D printed DENTCA Denture base II, NextDent^TM Base) were used. And 4 types denture relining materials (Tokuyama Rebase II fast, Kooliner, Denture Liner, Denture Liner, Lang Jet Denture Repair Kit) with different components were used. It was classified into 12 groups. Adhesion was performed between the resin base and the relining materials in accordance with ISO/TS 11405 standard. The shear bonding strength was measured, and then the adhesion interface was observed with a stereoscopic microscope and a scanning electron microscope. The fracture pattern was investigated through the analysis of the fragment. Results: In the 3D printed denture resin group, the shear bonding strength with relining materials was significantly lower than that of the heat-cured resin group (P < 0.05). The group of polymethyl methacrylate -based relining materials, high shear bonding strength was shown regardless of the type of denture. As for the fracture pattern, adhesive fracture appeared in most groups, and cohesive, mixed fracture appeared in some groups. Conclusion: The polymethyl methacrylate -based denture relining materials showed high shear bonding strength values compared to other denture relining materials. But, for direct methods, it is considered advantageous in terms of shear bonding strength to use a isobutyl methacrylate-based denture relining materials.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.140-146
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• 2013

PURPOSE. The aim of this study was to investigate the destructive effects of biofilm formation and/or biocorrosive activity of 6 different oral microorganisms. MATERIALS AND METHODS. Three different heat polymerized acrylic resins (Ivocap Plus, Lucitone 550, QC 20) were used to prepare three different types of samples. Type "A" samples with "V" type notch was used to measure the fracture strength, "B" type to evaluate the surfaces with scanning electron microscopy and "C" type for quantitative biofilm assay. Development and calculation of biofilm covered surfaces on denture base materials were accomplished by SEM and quantitative biofilm assay. According to normality assumptions ANOVA or Kruskal-Wallis was selected for statistical analysis (${\alpha}$=0.05). RESULTS. Significant differences were obtained among the adhesion potential of 6 different microorganisms and there were significant differences among their adhesion onto 3 different denture base materials. Compared to the control groups after contamination with the microorganisms, the three point bending test values of denture base materials decreased significantly (P<.05); microorganisms diffused at least 52% of the denture base surface. The highest median quantitative biofilm value within all the denture base materials was obtained with P. aeruginosa on Lucitone 550. The type of denture base material did not alter the diffusion potential of the microorganisms significantly (P>.05). CONCLUSION. All the tested microorganisms had destructive effect over the structure and composition of the denture base materials.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.523-531
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• 1993

The purpose of this study was to investigate the color change of denture base resins by coffee. Denture base resins for this study were Triad VLG Denture Base (Dentsply, York Div. U.S.A.), Premium Super-20 (Lang Dental Mfg. Co., Inc., U.S.A.) for denture base, Toughron Rebase (Miki Chemical Prod., Kyoto, Japan), Jet Repair Acrylic (Lang Dental Mfg. Co., Inc., U.S.A.), Triad Reline (Dentsply, fork Div. U.S.A.) and Tokuso Rebase (Tokuyama Soda Co., Ltd., Japan) for denture rebase. Twenty specimens of each denture base resin were made and polished. The color of specimens was measured by colorimeter (Model Tc-6FX, Tokyo Denshoku Co. Japan), and they were stored in coffee for three weeks and then color changes were measured. The obtained results were as follows : 1. The L*, a*, b* and the E*ab values of all denture base resins were changed after three weeks. 2. The amount of color change on L*, a*, b* and the E*ab value of each specimens showed different patterns. 3. The b* values of Triad Reline materials were changed more than the other materials. 4. The E*ab values of Triad Denture Base materials were changed more than the other materials.

• The Journal of Advanced Prosthodontics
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• v.3 no.3
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• pp.136-139
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• 2011

PURPOSE. A new light curing urethane dimethacrylate and a cold curing resin with simpler and faster laboratory procedures may have even improved flexural properties. This study investigated the 3-point flexural strengths and flexural moduli of two alternate base materials. MATERIALS AND METHODS. A cold curing resin (Weropress) and a light curing urethane dimethacrylate base material (Eclipse). Along with Eclipse and Weropress, a high impact resin (Lucitone199) and three conventional base materials (QC 20, Meliodent and Paladent 20) were tested. A 3-point bending test was used to determine the flexural strengths and flexural moduli. The mean displacement, maximum load, flexural modulus and flexural strength values and standard deviations for each group were analyzed by means of one-way analysis of variance (ANOVA) (with mean difference significant at the 0.05 level). Post hoc analyses (Scheffe test) were carried out to determine the differences between the groups at a confidence level of 95%. RESULTS. Flexural strength, displacement and force maximum load values of Eclipse were significantly different from other base materials. Displacement values of QC 20 were significantly different from Lucitone 199 and Weropress. CONCLUSION. The flexural properties and simpler processing technique of Eclipse system presents an advantageous alternative to conventional base resins and Weropress offers another simple laboratory technique.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.5
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• pp.525-535
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• 2002

The purposes of this study were to evaluate the adherence of bacteria on various denture base resin materials and effects of chitosan, added to denture base materials on bacterial adherence. PMMA denture base resin such as heat-cured Vertex-RS, self-cured Vertex-SC and 4-META denture base resin such as heat-cured Meta-Dent, self-cured Meta-Fast were used in this study Samples were divided into two groups the denture base resin with chitosan, without chitosan Streptococcus mutans and Lactobacillus casei were used in this study. The surface of samples was observed by SEM. When chitosan was added to M17 and MRS broth, viable cell count of bacteria was reduced. Viable cell count of Streptococcus mutans on the samples decreased as follows : Meta-Dent, Vertex-SC, Meta-Fast, Vertex-RS. Viable cell count of Lactobacillus casei on the samples decreased as follows: Vertex-RS, Meta-Dent, Meta-Fast, Vertex-SC. The resin with chitosan showed lower adherence of bacteria than without chitosan. The images of SEM showed that the surface of the resin with chitosan was rougher than that of without chitosan. These results showed that the denture base resin materials with chitosan have rougher surface than without chitosan, but less bacteria adhered on them.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2257-2262
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• 2014

$C_{60}$ is widely investigated because of its unique structure. But its applications in solid propellant seem to be relatively neglected. $C_{60}$ has more outstanding features than carbon black which is widely used as a catalyst ingredient of solid propellant. To combine the advantages of fullerene and lead salts, another good composite in propellant catalysts, we synthesized a kind of fullerene phenylalanine lead salt (FPL) and explored its thermal performances by differential thermal analysis (DTA) and thermogravimetry analysis (TGA). The results show it undergoes four exothermic processes started from 408 K. Combined TGA and X-ray diffractometer (XRD), the decomposition mechanism of FPL was derived by TG-IR and comparing IR spectra of FPL and its residues after burned to $327^{\circ}C$, $376^{\circ}C$ and $424^{\circ}C$, respectively. Effect of FPL on the decomposition characteristic of hexogen (RDX), a type of explosive in propellant, has been investigated using DTA at different heating rate, which shows the decomposition temperatures of the explosive are all reduced by more than 20 K. The corresponding activation energy ($E_a$) is decreased by $30kJ{\cdot}mol^{-1}$. So FPL has potential application as a combustion catalyst in solid propellant.

• The Journal of Advanced Prosthodontics
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• v.12 no.6
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• pp.376-382
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• 2020

PURPOSE. To determine the shear bond strengths of different denture base resins to different types of prefabricated teeth (acrylic, nanohybrid composite, and cross-linked) and denture teeth produced by computer-aided design/computer-aided manufacturing (CAD/CAM) technology. MATERIALS AND METHODS. Prefabricated teeth and CAD/CAM (milled) denture teeth were divided into 10 groups and bonded to different denture base materials. Groups 1-3 comprised of different types of prefabricated teeth and cold-polymerized denture base resin; groups 4-6 comprised of different types of prefabricated teeth and heat-polymerized denture base resin; groups 7-9 comprised of different types of prefabricated teeth and CAD/CAM (milled) denture base resin; and group 10 comprised of milled denture teeth produced by CAD/CAM technology and CAD/CAM (milled) denture base resin. A universal testing machine was used to evaluate the shear bond strength for all specimens. One-way ANOVA and Tukey post-hoc test were used for analyzing the data (α=.05). RESULTS. The shear bond strengths of different groups ranged from 3.37 ± 2.14 MPa to 18.10 ± 2.68 MPa. Statistical analysis showed significant differences among the tested groups (P<.0001). Among different polymerization methods, the lowest values were determined in cold-polymerized resin.There was no significant difference between the shear bond strength values of heat-polymerized and CAD/CAM (milled) denture base resins. CONCLUSION. Different combinations of materials for removable denture base and denture teeth can affect their bond strength. Cold-polymerized resin should be avoided for attaching prefabricated teeth to a denture base. CAD/CAM (milled) and heat-polymerized denture base resins bonded to different types of prefabricated teeth show similar shear bond strength values.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.219-223
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• 2001

The on-line cure monitoring during the cure process of composite materials is important for better quality and productivity. The dielectric sensor for cure monitoring consists of base film and electrodes. Because the characteristic of dielectric sensor for the on-line cure monitoring is dependent on the base material, width and number of electrode, etc, the dielectric sensor should be standardized. And the selection of base film material of sensor is very important. In order to prevent the measuring errors generated from the increase of environmental temperature, the base film material should have stable dielectric constant with respect to environmental temperature. In this study, the newly developed dielectric sensor for cure monitoring was designed and the dissipation factor which is function of degree of cure was measured using the sensor. The relationship between the dissipation factor and degree of cure with respect to environmental temperature was investigated.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.79-100
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• 1989

The Purpose of this study was to investigate material differences in stress transmission among various artificial teeth and denture base materials. For this study, a two-dimensional finite element model and a two-dimensional photoelastic model of a mandible with complete denture were made. A resin tooth and a porcelain tooth were used as artificial teeth, and a resin base, a metal lined base, and a soft-liner lined base were used as denture bases. An occlusal load was applied and principal stresses generated in the supporting tissues were compared. To test the impact stress transmission, strain gauge attached to the denture base specimens made of the different materials were made in thick and thin groups. Voltage outputs from hitting the specimen with a steel ball were compared. The results were as follows : 1. In FEM, increasing the mucosal thickness reduced the maximum principal stresses in the supporting tissues, but altering the tooth materials and the base materials induced no difference in the stresses. 2. In photoelastic model study, no difference in fringe order among the specimens were observed, but the thick mucosa group and the soft-liner lined group revealed a more uniform distribution of the load. 3. In strain measuring, the impact force transmission was highest in the soft-liner lined group, and was the lowest in the metal lined group(p<0.01). 4. In the thin group using the resin base, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the thick group. In the soft-liner lined group, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the metal lined group. 5. The thick group showed lower impact stress transmission than the thin group(p<0.01).