The purpose of this study was to evaluate the surface roughness of Ni-Cr-Be alloy(Verabond ~, Aalba Dent Inc. USA) according to electrolyte concentration and etching time. Total of 150 metal specimens (12x 10 X 1.5mm) composed of 5 polisded specimens, 5 sandblasted specimens, 140 etched specimens were prepared. Etched groups were divided into 28 groups by the HC1O4 con= centrations(10, 30, 50, 70%) and etching times(15, 30, 60, 120, 180, 240, 300 seconds). The mean surface roughness(Ra) and the etching depth were measured with Optical 3-dimensional surface roughness measuring machine(Accura 1500M, Intek Engineering Co., Korea) and observed under SEM. The results obtaind were as follows 1. Surface roughness(Ra) and etching depth were affected by the order of etching time, electrolyte concentration, and their interaction (NO.05) . 2. Surface roughness(Ra) and etching depth were increased with etching time in 10%, 30% electrolyte concentrations, but they had no significant difference with etching time in 70%(P<0.05). 3. Surface roughness(Ra) and etching depth decreased in the order of 30, 10, 50, 70% electrolyte concentrations from 120 seconds etching time(p<0.05). 4. The remarkable morphologic changes in etched surface were observed along the grain boundaries in 15, 30 seconds of 10%, 30% concentrations and the morphologic changes could be denoted in the grains themselves as well as along the boundaries with the lapse of time. Even though the noticeable morphologic changes also took place in etched surface with 50% concentration, the degree of changes were less than that of changes with 10%, 30%. However, there were little morphologic changes with 70% concentration regardless of etching time. 5. Surface roughness(Ra) of sandblasting group with 50um A1203 had no significant difference with 30%-30 seconds etched group(p<0.05).
Alloys* ; Edible Grain

The purpose of this study was to evalute the corrosion resistance of chemically and thermally recycled metal brackets. In vivo, two types of recycled metal brackets and new brackets were directly bonded for 1 year, and then the microstructure of bracket surface was examined by S.E.M. (J.S.M.-840 Scanning Electron Microscope, Japan). The following results were obtained. 1) The microstructure of new and chemically recycled metal bracket surfaces showed regular structure without island formation and recrystallization; and after 1 year, the same appearance except some scratches. 2) The microstructure of thermally recycled metal bracket surfaces showed a beginning of island formation and recrystallization by annealing, and after 1 year, a typical corrosive appearance, completely island formation with some metal grains by recrystallization. 3) Chemically recycled metal brackets showed better corrosion resistance than thermally recycled metal brackets.
Edible Grain ; Corrosion*

We report a case of warty dyskeratoma in a 65-year-old man. He had a asymptomatic solitary 1 x 1 cm sized, round, light-brownish colored, centrally depressed nodule on the right forehead for several yearss. Histopathological findings showed two large cup-shaped keratin-filled invagination of acanthotic epidermis, suprabasal cleft formation with corps ronds, grains and numerous villi at the lower portion of the invagination, the characteristic features of warty dyskeratoma.
Aged ; Edible Grain ; Epidermis ; Forehead ; Humans

We report a case of warty dyskeratoma in a 59-year-old man. For 10 years, he had had an asymptomatic solitary 0.5x0.5 cm sized, erythematous, hard papule with a yellowish, central keratotic plug on the vertex. Histological findings showed a large cup-shaped, keratin-filled invagination of acanthotic epidermis, and a suprabasal cleft formation with corps ronds, grains and numerous villi at the lower portion of the invagination, the characteristic features of warty dyskeratoma.
Edible Grain ; Epidermis ; Humans ; Middle Aged ; Scalp*

PURPOSE: This study aimed to identify the effects of the sintering conditions of dental zirconia on the grain size and translucency. MATERIALS AND METHODS: Ten specimens of each of two commercial brands of zirconia (Lava and KaVo) were made and sintered under five different conditions. Microwave sintering (MS) and conventional sintering (CS) methods were used to fabricate zirconia specimens. The dwelling time was 20 minutes for MS and 20 minutes, 2, 10, and 40 hours for CS. The density and the grain size of the sintered zirconia blocks were measured. Total transmission measurements were taken using a spectrophotometer. Two-way analysis of variance model was used for the analysis and performed at a type-one error rate of 0.05. RESULTS: There was no significant difference in density between brands and sintering conditions. The mean grain size increased according to sintering conditions as follows: MS-20 min, CS-20 min, CS-2 hr, CS-10 hr, and CS-40 hr for both brands. The mean grain size ranged from 347-1,512 nm for Lava and 373-1,481 nm for KaVo. The mean light transmittance values of Lava and KaVo were 28.39-34.48% and 28.09-30.50%, respectively. CONCLUSION: Different sintering conditions resulted in differences in grain size and light transmittance. To obtain more translucent dental zirconia restorations, shorter sintering times should be considered.
Ceramics ; Edible Grain ; Light ; Microwaves ; Zirconium

The purpose of this study is to investigate which current densities and etching times will result in an optimal etching depth and surface roughness when an Ni-Cr-Be alloy is etched with 30% perchloric acid(HClO4 ). For this study,observations were made by means of an optical three-dimen-sional surface roughness measuring machine and a scanning electron microscope. The etchings took place under the following conditions using current densities of 300mA/cm2, 450mA/cm2, 600mA/cm2 and 750mA/cm2, and using etching time of three, five, six, seven and nine minutes. Under the conditions, the experiments reached the following conclusions. 1. When the current density is above 450mA/cm2 and the etching time is longer than five min-utes, the etching depth increased as the current density and etching time increased. And the surface roughness was significantly influenced by the interaction of the current density and etching time. 2. Under the etching conditions of 600mA/cm2 and five minutes, the optimal etching depth for a resin cement space and the highest surface roughness for mechanical retention were obtained. The etching depth and surface roughness were 32.86 micrometer and 7.90 micrometer, respectively. 3. Observations under the scanning electron microscope showed that both the corrosion at the grain boundary and the corrosion within the grain occurred on the etched surface. It was also observed that the corrosion at the grain boundary became more severe as the current density and etching time increased. In addition, at higher current densities and longer etching times, general corrosion appeared.
Alloys* ; Edible Grain ; Corrosion ; Resin Cements

Heat treatment which removes internal stress enhances the mechanical properties of the orthodontic arch wire. The main purpose of this experiment was to investigate the effects of the heat treatment on the mechanical properties of the Elgiloy wire. The Elgiloy wire, 0.016" X 0.022" and 0.018" X 0.025", were heat treated in an electric oven for 5, 10 and 15 minutes at selected temperatures between 300 and 900degreesC. Tensile strength and load deflection rate were measured to reveal the changes of mechanical property at various con?ditions, and each specimen was observed under metallurgic microscope. Also to trace the precipitation material due to overheat treatment, a qualitative analysis was carried out with EDS system. It was found that heat treatment at a low temperature caused an increase in the tensile strength and bending resistance, and a maintenance in the fibrous in the tensile strength and bending resistance, and a maintenance in the fibrous structure of both sizes of wire. The changes observed in properties and appearance were probably due to the relief of internal stresses incurred in the metal during cold working. In both sizes of wire the tensile strength and the bending resistance continued to decrease at high temperature, and the fibrous structure continued to disappear then was not observed at 900degreesC. The carbide precipitation founded in grain boundary at 750degreesC probably was other elements carbide (Ni, Co) except Cr. The grain growth was observed at 1100degreesC. Optimum heat treatment for the 0.016" X 0.022" Elgiloy wire was 10 minutes at 500degreesC, and for the 0.018" X 0.025" Elgiloy wire it was 5 to 15 minutes at 500degreesC.
Edible Grain ; Hot Temperature* ; Tensile Strength

Cerebral paragonimiasis, occurring as an extrapulmonary infestation, is one of the important intracranial lesions in Korea. In this paper we report a case of cerebral paragonimiasis which showed very similar C-T findings to pyogenic brain abscess and was verified by pathologic research. Though we don't have much experiences in the diagnosis of the cereal paragonimiasis with C-T Scan, we found out some differences between pyogenic abscess and that due to cerebral paragonimiasis in several aspects.
Abscess ; Brain Abscess* ; Brain* ; Edible Grain ; Diagnosis ; Korea ; Paragonimiasis*

PURPOSE: This study is intended to understand the sensitometric charac teristics and the emulsion properties of the commercially available CEA TVS film in comparison with the Kodak X-Omat V film. MATERIAL AND METHODS: For this purpose, we have formulated an analytic expression of the characteristic curves for x-ray film exposed to mixed radiation of electrons, photons, and visible light. This mathematical expression was developed based on reaction-rate and target-hit theories. Unlike previous expressions, it relates optical density to emulsion properties such as grain size and silver bromide content. We have also developed a quantity which characterizes the film response to visible light relative to that to photons and electrons. This quantity could be expressed as a function of grain area. Thus, we have developed mathematical expressions and quantities with which the emulsion properties of the films can be revealed based on the sensitometric characteristics. Demonstrating the use of this analytical study, we exposed CEA and Kodak verification films to the mixed radiation of electrons, photons, and visible light, and interpreted the experimental results accordingly. RESULTS: We have demonstrated that: (1) the saturation density increases as the silver bromide content increases, (2) the time required to reach the threshold dose (to which the film begins to respond) when films are exposed to visible light decreases as the grain size increases, and (3) the CEA film contains more silver bromide, whereas the Kodak film contains larger grains. These findings were supported by the data provided by the manufacturers afterward. CONCLUSION: This study presented an analytical and experimental basis for understanding the response of X-ray film with respect to the emulsion properties.
Edible Grain ; Light ; Photons ; Silver ; X-Ray Film

The purpose of this study was to prove that an intermediate resin layer (IRL) can increase the bond strength to dentin by reducing the permeability of single-step adhesives. Flat dentin surfaces were created on buccal and lingual side of freshly extracted third molar using a low-speed diamond saw under copious water flow. Approximately 2.0 mm thick axially sectioned dentin slice was abraded with wet #600 SiC paper. Three single-step self-etch adhesives; Adper Prompt L-Pop (3M ESPE, St Paul, MN, USA), One-Up Bond F (Tokuyama Corp, Tokyo, Japan) and Xeno III (Dentsply, Konstanz, Germany) were used in this study. Each adhesive groups were again subdivided into ten groups by; whether IRL was used or not; whether adhesives were cured with light before application of IRL or not; the mode of composite application. The results of this study were as follows; 1. Bond strength of single-step adhesives increased by an additional coating of intermediate resin layer, and this increasement was statistically signigicant when self-cured composite was used (p < 0.001). 2. When using IRL, there were no difference on bond strengths regardless the curing procedure of single-step adhesives. 3. There were no significant difference on bond strengths between usage of AB2 or SM as an IRL. 4. The thickness of hybrid layer was correlated with the acidity of adhesive used, and the nanoleakage represented by silver deposits and grains was examined within hybrid and adhesive layer in most of single-step adhesives. 5. Neither thickness of hybrid layer nor nanoleakage were related to bond strength.
Adhesives* ; Edible Grain ; Dentin* ; Diamond ; Molar, Third ; Permeability ; Silver ; Water