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*

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

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*

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

This study compared levels of whole grain consumption-related predisposing, reinforcing, and enabling factors according to socio-demographic variables, and examined how these factors are associated with whole grain consumption frequency among Korean adults. A survey questionnaire was administered to a convenience sample of adult males and females aged 20~59 years (n=300). The questionnaire included questions on predisposing, reinforcing, and enabling factors in relation to whole grain consumption as well as a brief whole grain food frequency questionnaire. Female subjects showed a significantly higher level of negative beliefs on health.nutrition.taste.texture while showing a significantly lower level of social support compared to that of males. The age group of 40~59 years showed a significantly higher social support level than the age group of 20~39 years. Results from multivariate regression analyses showed that different combinations of predisposing, reinforcing, and enabling variables were significant in predicting whole grain consumption frequency according to sex and age. The study findings can be used for developing specific target-oriented nutrition intervention programs for promotion of whole grain intake among Korean adults.
Adult* ; Causality* ; Edible Grain* ; Female ; Humans ; Male ; Surveys and Questionnaires

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

Sixty mongrel dogs were divided into three groups of twenty dogs. One group of twenty dogs underwent placement of a rigid reconstruction plate (2.7mm thickness of plates and 3.0mm diameter of screws, Richards plating system, stainless-steel) and labeled normal mandibles stress shielded (NMSS) group. Another group of twenty dogsundeuuent cancellous cellular bone grafts of 3.5cm in length and a rigid reconstruction plate. In this group the plates were left in place until the time of sacrifice(1460 days) The group was labeled as a bone grafted mandibles stress shielded (BGSS). Ten dogs of each group were sacrificed at day 60. Another ten dogs of cach group were sacrificed at day 1460. In addition, all intitial resection specimens were processed for histomorphometry on trabecular bone area(TBA) as a normal non-stress shielded reference value of day-0 control (NMNSS) group. The histomorphometric results are as follows. Average percentage of TBA at day 0 control in NMNSS group was 44+/-5%. Average percentage of TBA in NMNSS group at 60 days was 42+/-6% , and that at 1460days was 42+/-4%. Average percentage of TBA in NMSS group at 60days was 47+/-6%, and that at 1460days was 44+/-4%, while average percentage of TBA at day 0 control was 44+/-5% (pinot available). Average percentage of TBA in BGNSS group at 60 days was 67+/-4, and that at 1460 days was 65+/-4%, while average percentage of TBA in day o control was 44+/-5%. BGNSS group shows, once each mandible was bone grafted at 60 days, that bone density was increased due to the high cellular bone grains. But after 1460 days there are little significant change, and that they are stable for four years(p<.001). Average percentage of TBA in BGSS group at 60 days was O+/-6, and that at 1460 days was 66+/-4% , while average percentage of TBA at day O control was 44+/-5%. BGSS group with the plate left in place for 4 years also shows the enhanced bone trabecular percentage at 60 days due to the high cellular bone grafts, but after 60 days until 4 years still little significant change(p<.001). The result data indicates the stress shielding from the rigid reconstruction plate on the mandible is not valid. It is suggested that clinicians do not need to remove reconstruction plates for fear of stress shielding.
Animals ; Bone Density ; Edible Grain ; Dogs* ; Mandible ; Reference Values ; Transplants*