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*

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

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

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

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

Recently, it is reported that intervention of oral nutritional supplement improves the nutritional status of cancer patients, and the effectiveness is affected by the sensory preference of cancer patients on the oral nutritional supplement. However, the variety of oral nutritional supplement is extremely limited and the number of patient's benefits from using the products are restricted mostly due to sensory dislikes. The objective of this study was to provide sensory preference score of trial manufactured products with different accessory ingredients to maximize the use of oral nutritional supplements. Cancer patients (n = 30) and age, sex-matched healthy volunteers (n = 30) participated in the sensory assessments (taste, flavor, viscosity, color and overall preference) of three types of oral supplements (cereal base, cereal base+herb and cereal base+fruit) and a control supplement product with scorched cereal flavor, a top seller in current Korean market. Results indicate that the cancer patients' overall preference was significantly higher for the control supplement, and fruit added supplement was preferred over plain cereal and herb added products, although the difference was insignificant. However, there was no significant preference difference for the supplements among the control group for all sensory factors. These results suggest that cancer patients are more sensitive to sensory preferences compared to the control group, and the patients prefer the flavor of cooked cereal which is a staple food in Korea.
Edible Grain* ; Fruit ; Healthy Volunteers ; Humans ; Korea ; Nutritional Status ; Viscosity

This study was conducted to evaluated the nutrition quality of the commercial supplementary foods for infants and young children and to seek a solution to the establishment of standards of nutrient requirements for supplementary foods in Korea. Information on food ingredients, nutrient contents, claims about usefulness of food components and instructions for feeding preparation were obtained from the labels of 33 commercial supplementary foods manufactured by 4 different domestic companies. According to the standard of supplementary foods for infants and young children described in the Korean Food Code, the commercial supplementary foods were categorized into two different types, weaning food and baby food. All the commercial weaning foods were in powder form and mainly composed of cereals, whereas all the baby foods were mainly composed of fruits in the form of canned juice. The weaning foods contained more nutrients than the baby foods did, and the nutrient levels of the weaning foods expressed as nutrient density on energy basis were higher than the RDA for infants aged 5 to 11 months, suggesting that the commercial weaning foods provide adequate amounts of nutrients. If one followed the instructions for feeding preparation appearing on the label, however, recommended amounts of intake of the weaning foods would provide too much energy as well as nutrients. There were many differences in nutrient standards of weaning foods between the Korean Food Code and Codex international food standard. In conclusion, the establishment of standards for nutrient requirements for the supplementary foods requires significant scientific studies on what nutrients are the most inadequate in Korean infants and young children feeds and what levels of nutrients should be added to the foods in order to supplement their nutrition. In addition, it is very important to have a strong scientific basis to support our standard when discrepancies exist between our standard and the international standard.
Edible Grain ; Child* ; Food Labeling ; Fruit ; Humans ; Infant* ; Korea ; Weaning

This in vitro study examined the effect of surface defects on cutting blades on the extent of the cyclic fatigue fracture of HEROShaper Ni-Ti rotary files using fractographic analysis of the fractured surfaces. A total of 45 HEROShaper (MicroMega) Ni-Ti rotary files with a #30/.04 taper were divided into three groups of 15 each. Group 1 contained new HEROShapers without any surface defects. Group 2 contained HEROShapers with manufacturing defects such as metal rollover and machining marks. Group 3 contained HEROShapers that had been clinically used for the canal preparation of 4-6 molars. A fatigue-testing device was designed to allow cyclic tension and compressive stress on the tip of the instrument whilst maintaining similar conditions to those experienced in a clinic. The level of fatigue fracture time was measured using a computer connected the system. Statistical analysis was performed using a Tukey's test. Scanning electron microscopy (SEM) was used for fractographic analysis of the fractured surfaces. The fatigue fracture time between groups 1 and 2, and between groups 1 and 3 was significantly different (p < 0.05) but there was no significant difference between groups 2 and 3 (p > 0.05). A low magnification SEM views show brittle fracture as the main initial failure mode. At higher magnification, the brittle fracture region showed clusters of fatigue striations and a large number of secondary cracks. These fractures typically led to a central region of catastrophic ductile failure. Qualitatively, the ductile fracture region was characterized by the formation of microvoids and dimpling. The fractured surfaces of the HEROShapers in groups 2 and 3 were always associated with pre-existing surface defects. Typically, the fractured surface in the brittle fracture region showed evidence of cleavage (transgranular) facets across the grains, as well as intergranular facets along the grain boundaries. These results show that surface defects on cutting blades of Ni-Ti rotary files might be the preferred sites for the origin of fatigue fracture under experimental conditions. Furthermore, this work demonstrates the utility of fractography in evaluating the failure of Ni-Ti rotary files.
Edible Grain ; Fatigue* ; Fractures, Stress* ; Microscopy, Electron, Scanning ; Molar