TITLE:
Trace elements on the surface of titanium implants extracted from rat bone
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe K, Hashimoto A*, Endo MM**
INSTITUTE:
Division of Dental Biomaterial Science, Department of Oral Health Science Niigata Univ. Graduate School of Medical and Dental Sciences
* Oral Health in Aging and Fixed Prosthodontics, Department of Oral Health Science, Niigata Univ. Graduate School of Medical and Dental Sciences
** 3rd Project Group, Research & Development Dept. MIZUHO IKAKOGYO Co., Ltd
JOURNAL:
Biomed Res Trace Elements 15(3) 262-264, 2004
KEYWORDS: dental implant, biocompatibility, X-ray photoelectron spectroscopy, calcium, phosphorus, bone formation.

ABSTRACT:
In order to make clear the relationship between the surface properties of a dental implant and biocompatibility, trace elements on the titanium surface of the implant extracted from a rat bone were examined. A cp Ti bullet, as a prototype, of 1.1 mm diameter and 3.5 mm length had a flat surface on its cylindrical side. The flat area was sandblasted by glassy particle and cleaned by argon sputtering. The surfaces of the implants extracted from the femur of Wistar rats were cleaned ultrasonically and examined by X-ray photoelectron spectroscopy (XPS). The detected main elements were Ti, O, C, and N. Ti peaks arise from the base material and the others indicate presence of bio-molecules including proteins. Trace elements, such as P, Ca and Si, were also detected. However, the Ca/P ratios were very small compared to those of calcium phosphate compounds, such as calcium diphosphate. This fact indicates that calcium phosphate compounds, including hydroxyapatite, don't form on the titanium implant in rat bone.

TITLE:
The Elements Analysis of the Tissue Section of the Lung Disease Caused by Environmental Pollution by Means of Electron Probe Microanalysis
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe K, Kobayashi,M*
INSTITUTE:
Division of Dental Biomaterials Science, Department of Oral Health Science, Niigata University Graduate School of Medical and Dental Science
* EPMA Laboratory, Center for Instrumental Analysis, Niigata University
JOURNAL:
Biomed Res Trace Elements 14 (4): 275-278, 2003
KEYWORDS: lung tissue section, trace analysis, environmental pollution, biopsy, diagnosis, electron probe microanalyser.

ABSTRACT:
Electron probe microanalysis (EPMA) equipped with wavelength dispersive spectrometers is one of the powerful instruments for detecting trace elements. We have applied this instrument to analyze trace elements in lung biopsy tissue section for diagnosis, such as hard metal lung. For this purpose, ultra pure carbon plate, in particular no contamination of Si, is required for detecting trace elements in tissue section. Using the carbon plate, we measured the element distributions in some lung biopsy sections that were obtained from the patients of occupational lung disease. As the result, some metallic elements, such as tungsten and titanium, were detected at the portion corresponding to the suspected area from histopathology. Hard metal lung was diagnosed. However, cobalt was not detected. In conclusion, by using ultra pure carbon plate, the usefulness of the section analysis by EPMA for lung disease diagnosis, such as hard metal lung, was confirmed.

TITLE:
New Method for quantitative mapping of metallic elements in tissue sections by electron probe microanalyzer with wavelength dispersive spectrometers
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K., Miyakawa,O., and Kobayashi,M. *
INSTITUTE:
Dental Materials and Technology, Faculty of Dentistry and *Center for Instrumental Analysis, Niigata University
JOURNAL:
Journal of Electron Microscopy 50(1), 77-82, 2001

ABSTRACT:
In this paper, we have proposed a new method that gives quantitative distributions of metallic elements in a tissue section by electron probe microanalyzer equipped with wavelength dispersive spectrometers. Its principal merit is the clear expression of element distribution with micrometer resolution in typically prepared section samples for routine histopathological diagnosis. By analyzing thin standard films containing metallic atoms of interest, it was confirmed that the detection limit is about 1 L 106 atoms mm-2. This value corresponds to 100 mgg-1 (dry weight) in case of tissue section of 2 mm thickness. Furthermore, for copper, iron and aluminum, the exact linear relationship between the amount of metallic atoms and the characteristic X-ray intensity was established in the range up to 15 L 106 atoms mm-2. The element maps of tissue sections from patients with Wilson's disease proved that the copper levels in analyzed areas were not homogeneous and indicated abnormal accumulation in some portions. These results confirmed the usefulness of this method for histopathological diagnosis.

http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11291964&dopt=Abstract

TITLE:
How Do We Analyze the Metallic Element Distribution in Tissue Section ?
-- New Application of Element Mapping by BPMA --
LANGUAGE:
in Japanese with English Abstract
AUTHORS:
Watanabe,K. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, Faculty of Dentistry and *Center for Instrumental Analysis, Niigata University
JOURNAL:
J of the Surface Science Society of Japan, 22(5): 332-336, 2001

ABSTRACT:
Electron probe microanalysis (EPMA) is a useful method for element mapping analysis. However, the samples to be subjected are restricted to heat-stable materials, such as metals and ceramics, because irradiation of focused electron beam generates intense heat. In order to apply EPMA to tissues, we sliced the samples off to sections of appropriate thicknesses by use of polished carbon block as a support, such sections were very stable against the intense electron beam. Thus the mapping analysis by EPMA has been applied to tissue sections for histopathologic diagnosis. The principal advantage of this method is high detection sensitivity that is about 1 x 106 at./mm2 in case of copper. This was confirmed by analyzing thin standard films containing the element. In addition, exact linear relationship between the amount of copper atoms and the characteristic X-ray intensity was established in the range up to 15 x 106 at./mm2. The usefulness of this method for histopathologic diagnosis, such as Wilson's disease, was confirmed by mapping analysis of many section samples.

TITLE:
New Partition Technique for Two-chamber Pressure Casting Unit for Titanium
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K., Okawa,S., Kanatani,M., Nakano,S., Miykawa,O. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, Faculty of Dentistry and *Center for Instrumental Analysis, Niigata University
JOURNAL:
Dental Materials Journal, 19(3): 307-316, 2000
ABSTRACT:
Although titanium has been widely used in prosthetic appliances, such as cast removable partial denture frameworks, high quality castings are still difficult to obtain. This study proposes a new partition technique using a metal foil for improving castability of a two-chamber pressure casting unit. The metal foil was formed beforehand to bring it in contact with the mold crucible wall so that no clearance was left behind it. Using this formed foil, the mold cavity can be completely isolated from the upper chamber and can be maintained in a vacuum even after the rupture of the foil. Accordingly, a large casting force is generated very quickly, and as a result, castability is expected to be significantly improved. This expectation was confirmed by the experiments using wax patterns including thin plate and mesh plate.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11218850&dopt=Abstract

TITLE:
Pilot production of Mousse-Up® based test food for swallowing function
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Matsunaga,K., Haishima,H., Haishima,K., Watanabe,K., and Yamada,Y.
INSTITUTE:
Department of Oral Physiology, Department of Pedodontics, Department of Dental Materials and Technology Niigata University School of Dentistry
JOURNAL:
J Japan Soc Stomatognathic Function 4:173-181, 1998

ABSTRACT:
Key words: swallow, electromyography, suprahyoid muscles, thickener, videofluorography

Abstract: A thickerner can be prepared in any desired viscosity to provide a foodstuff for training aid and/or examining aid for swallowing impairment, and various products have been introduced on the market. In this study, we designed a test food to be used as an examining aid with videofluorography, by mixing Mousse-Up® and Baritop® as the thickener and the contrast medium, respectively. The test food was prepared with various mixture ratios of Mousse-Up®, water, and Baritop®. It was then evaluated in such the specificity as texture and contrast as well as its mobility during swallowing.
Results are as follows:
1 . The thickener and contrast medium could be homogenized,
2 . Test foods could be prepared in any desired viscosity: liquid, soft, or hard, by changing the ratio between water and the thickerner.
Similar texture of test food to that of yogurt or rice gruel known as a training aid to the swallowing impaired could be prepared. The viscosity did not change when the test food was placed in a refrigerator for hours, thus the test food could be stocked in advance for the case.
3 . The contrast efficiency on the videofluorograph was enough to trace the food clearly while the subject swallowed it, and contrast medium added to the test food did not affect the characteristic in viscosity.
4 . To evaluate the mobility of test food during swallowing, electrical activities in the suprahyoid muscles were obtained from normal subjects.
When viscosity increased and/or volume of the food increased, the duration between the time when food bolus was formed and the time when the bolus was pushed back to the tongue base increased. Furthermore the bolus became difficult to be swallowed at a stroke. These results suggested that the form and the volume of food should be decided under the consideration of the swallowing function of patients.
The results suggest that the mixture made of Mousse-Up® and Baritop® cleaned the requirements as a test food for swallowing functions.

TITLE:
Possible Segregation Caused by Centrifugal Titanium Casting
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K., Okawa,S., Kanatani,M., Nakano,S., Miykawa,O. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
Dental Materials Journal, 15(2), 212-219, 1996
ABSTRACT:
The possibility of the segregation under solidification process using a centrifugal casting machine was investigated using an electron probe microanalyzer with elemental distribution map, line analysis and quantitative analysis. When a very small quantity of platinum was added to local molten titanium during the casting process, macroscopic segregation was observed under conditions of density difference of 0.1g/cm3 at the most, confirming that the centrifugal force of the casting machine is extremely strong. When a Ti -6Al-4V alloy was cast, however, no macroscopic segregation was observed. The centrifugal force of the casting machine examined in the present study hardly results in the body-force segregation in this titanium alloy.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9550020&dopt=Abstract

TITLE:
Molten Titanium Flow in U-type Cavity
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Kanatani,M., Nakano,S., Miykawa,O. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 15(6), 532-539, 1996
ABSTRACT:
By combining information from X-ray transparency and from molten titanium flow, the casting process in a U-type cavity simulating crown section was investigated under several conditions,such as type of casting machine or sprue diameter. Despite the machine type, centrifugal (CT) or two-chamber pressure (PR) machine, jet flow and F-type filling were observed in the occlusal area. The flow pattern in the axial area, however, was controlled by the main body force of each casting machine; it was the B-type for PR and the F-type for CT. Major factors related to internal defects were sprue diameter for PR and sprue-attachment position and angle for CT.

TITLE:
Difference in Molten Metal Flow Between Pure Titanium and Ti-6Al-4V alloy
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Kanatani,M., Nakano,S., Miykawa,O. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 15(2), 137-145, 1996
ABSTRACT:
To investigate the difference in castability between pure titanium and Ti-6Al-4V alloy, three types of casting that differed in mold filling type were constructed. Casting defects were checked by X-ray transparencies and flow behavior was observed using the molten tracer element method. There was no difference between the two metals for F type fillings. However, for thin cavities (W type fillings) and mesh cavities (B type fillings), the castability of the titanium alloy was slightly lower than that of pure titanium. The thermal properties of the titanium alloy are presumed to be considerably different from those of pure titanium since platinum, one of the tracers, was hardly detected during mesh casting of the alloy. Microanalysis of the top of the mesh casting revealed that the molten alloy flow included many particles. In conclusion, the reason for the poorer castability of the titanium alloy is that the viscosity of the molten alloy increased significantly because of the solidification particles included in its flow.

TITLE:
Study on the One Chamber Pressure Casting Machine for Titanium
Part 2 Influence of the Mold Permeability on Casting Defects
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Kanatani,M., Nakano,S., Miykawa,O. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 14(6), 668-676, 1955
ABSTRACT:
Casting defects and titanium flow using a one-chamber pressure casting machine were observed by the transparent X-ray method and the molten tracer element method, respectively. To clarify the relation between casting defects and filling types, three types of wax patterns were invested at one time. To estimate the influence of permeability, three types of investment which significantly differed in permeability were used. As a result, investments with high permeability cause many internal defects in thick plate castings and external defects on thin plate castings and mesh castings. Their defects were closely related to the flow in the cavity. Low permeable investment caused few casting defects despite the cavity type.

TITLE:
Study on the One Chamber Pressure Casting Machine for Titanium
(1) Relation between Casting Properties and the Applied Pressure
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 14(4), 378-386, 1995
ABSTRACT:
To clarify the casting properties of a one chamber casting machine, defects and titanium flow in the castings were examined by transparent X-ray photographs and a flow visualization technique. The results were compared with those obtained previously using a two chamber machine. Flow observations showed that the inflow of the fomer machine was faster, due to the higher pressure (7Kg/cm2) applied suddenly. In a thick cavity, turbulent flow sometimes occurred and in such a case many large internal defects were generated because solidification of the shell finished later than that of laminar flow. In thin cavity, external defect occurred because the filling times were longer those that of pressure elevation in the cavity due to the diffusion of argon. In both types of cavity, almost complete castings were sometimes obtained. This uncertainty was caused from the indeterminate permeability of cavity wall. In a complicate cavity consisting of thick and thin portion, internal defect in the thick area and external defect in the thin area were observed.

TITLE:
Titanium Flow Change with Time Caused by the Solidification Layer at Early Stage
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Honma,H., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 14(1), 52-58, 1995
ABSTRACT:
Titanium flow change with time was examined in the case of plate cavities. A very unsteady flow was recognized by means of flow observation of the casting surface and the section. In the thick cavity (1.4mm), a solidification shell was formed of an early stage, and then later inlet fluid was solidified after filling the cavity. As a consequence of that process, large inner defects are liable to generate within the shell. In the thin cavity (0.55mm), the solidification layer which was generated by early inlet flow markedly narrowed the fluid passage, so that the later inlet fluid hardly proceeds the same path because of the large friction, and generated the new passage as a bypass. Large inner defects rarely generated but outer defects tended to occur. In conclusion, unsteady flow strongly affects the generation of casting defects.

TITLE:
Interface Reactions between Titanium and Porcelain during Firing
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Honma,H., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 12(5), 620-629, 1993
ABSTRACT:
To clarify the interface reaction between porcelain and pure titanium during porcelain firing, an electron probe microanalyzer (EPMA), X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) were used to characterize the interface that was revealed after mechanically peeling. Separation occurred partly at the interface between titanium and porcelain and partly slightly inside the porcelain after firing three times at 760C. In the surface layer of the titanium side, only oxygen was detected as a diffusing element. Redox reaction was deduced from the X-ray diffraction results which indicated a decrease in Sn oxide and revealed beta-Sn (metallic Sn). A considerable amount of Ti hemi-oxide was formed at the interface when fired at 760C for two minutes.

TITLE:
Comparative Study of Pressure Casting and Centrifugal Casting on Molten Titanium Flow
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Honma,H., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 12(4), 496-505, 1993
ABSTRACT:
One of the determining factors governing the titanium flow in a mold cavity is the intensity of the casting force, including its direction. Actual casting force is the pressure applied to the narrow orifice of the cavity even in the case of the centrifugal casting. The filling areas and theflow nature were observed by the X-ray radiographs and the flow patterns became apparent from the tracer (Pd) distribution maps. The results of these experiments have proved that the most significant factor influencing the flow behavior in the mold cavity is the intensity of the body force, the gravity or the centrifugal force. Furthermore, external and internal defects in the titanium castings are also influenced by this factor.

TITLE:
Effect of Argon Gas on the Molten Titanium Flow in a Mesh Cavity
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Honma,H., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 11(5), 808-816, 1992
ABSTRACT:
Using a centrifugal casting machine for titanium, the effect of gas conversion, in air or in argon, on the titanium flow was investigated in the case of a mesh pattern. This factor exerted a profound influence on the shape of filled area rather than the castability. In argon, the early inflow reached the farthest portion of the mesh cavity, which was not observed in air. The flow observation indicated that the titanium flow in the cavity was laminar in argon or turbulent in air. In the case of laminar flow, the character of the centrifugal casting appeared more clearly where the driving force of flow was its velocity even in such a complicated pattern.

TITLE:
Relationship between Titanium Flow and Casting Contamination Caused by Mold Materials
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Honma,H., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 11(4), 662-671, 1992
ABSTRACT:
The interface reaction between molten titanium and quartz glass in the casting process was investigated from the standpoint of the flow nature in the mold cavity. The quartz glass by contact with the molten titanium was decomposed into oxygen and silicon. The former together with titanium formed the outermost layer known as alpha-case. The latter is preferentially dissolved into the molten titanium to form the contaminated layer. The molten titanium including the silicon can cause the inner contamination region by the mechanisms of (1) surface concave defects, (2) collision of some streams,and (3) "ejection" in a turbulent flow. Furthermore, the viscosity of molten titanium necessarily increases by contamination and then resistance to flow increases, by which the castability can be affected.

TITLE:
Titanium Flow Patterns caused by Entrance Velocity
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 11(2), 297-307, 1992
ABSTRACT:
Several experiments were carried out under small casting forces to study the relationship between the entrance velocity of molten titanium and the flow pattern in the mold cavity. When the spring of the centrifugal casting machine was wound up to 20 (the manufacture's instruction is 38), the flow was turbulent and its pattern was analogous to that of 38 winds, and when it was wound up to 10, a laminar flow was observed. When the pressure casting machine was operated with the pressure adjusted to 0.6 kg/cm2 (the manufacture's instruction, 1.1 kg/cm2), the flow patterns were altered appreciably and pressure dependence of internal defects varied with the position of the sprue. In addition, the influence of various conditions on the entrance velocity, such as casting force, was theoretically considered.

TITLE:
Molten Titanium Flow in a Mesh Cavity by the Flow Visualization Technique
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
Dental Materials Journal, 10(2), 128-137, 1991
ABSTRACT:
The tracer element molten (TEM) method, which provides titanium flow visualization in a mold cavity, was applied to investigate the flow in a mesh pattern. When a pressure casting machine was used, most of the mesh rods were composed of many solidification layers, which implied that the flow was laminar and almost steady. When a centrifugal casting machine was used, the flow was almost irregular and a stack of solidification layers was observed in only a few segments. These results indicate that the flow was turbulent. In a complicated cavity, such as a mesh pattern, pressure rather than centrifugal force acts as an effective casting force. Therefore, in such a cavity, favorable castability can be achieved with high pressure and laminar flow.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1820837&dopt=Abstract

TITLE:
Research on Titanium Flow by "Tracer Element Molten Method" in the Dental Precision Casting
2. Relationship Between the Titanium Flow in Plate Molds and the Casting Defects
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 10(1), 77-96, 1991
ABSTRACT:
The relationship between the titanium flow in plate molds visualized by the tracer element molten method and the casting defects has been investigated. In the case of Cyclarc, laminar flow, which tends to cause the large internal defect at the center of the vortex, was observed. The solidification shell of the pattern was usually made at an early stage. In the case of Titaniumer, a turbulent flow was observed, and the intense centrifugal force affected the filling process in the mold and the distribution of small porosities. In the thinner molds, the obstruction of subsequent flows by the initial solidification layers provides a new type of filling for the mold.

TITLE:
Determination of Titanium Flow by the Tracer Element Molten Method in the Dental Precision Casting 1. The Principle of Flow Visualization and Application to Simple Castings
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N., and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 9(4), 623-632, 1990
ABSTRACT:
The tracer element molten (TEM) method has been developed for flow visualization of molten Titanium in dental precision casting. The principle of this technique is as follows. When Titanium is cast, the tracer element wire inserted previously into the selective point of the sprue is molten little by little and distributed according to the molten Titanium flow in the mold cavity. After solidification, to observe the flow pattern, the tracer element needs to be analyzed on a section of the casting by EPMA equipped with the stage scan mapping system. This technique using Ag, Au, Pd or Pt as a tracer has been applied to some simpler castings in shape and has been confirmed to be a very powerful technique for Titanium flow visualization in dental castings.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2134828&dopt=Abstract

TITLE:
Reactions at the Nonprecious Metal-Ceramic Interface during Porcelain Firing
(III) -- A Commercial Alloy Forming Much Cr Oxide during Firing --
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 9(3), 453-462, 1990
ABSTRACT:
To examine the interface reaction between porcelain and a commercial Ni-Cr dental alloy (containing higher Cr and Mo) during porcelain firing, electron probe microanalyzer (EPMA) and X-ray diffraction have been used to characterize the interface which has emerged by means of selective dissolution of the alloy caused by a bromine-methanol solution. Much Cr oxide was formed at the early stage of firing, and remained in the reaction layer even if the holding time at 960C was up to 8 minutes. As a result, many Cr atoms diffused into the porcelain layer, most of which was found to form oxides through X-ray diffraction. Moreover, the porcelain layer nearest to the oxide layer was deduced to be modified seriously.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2135535&dopt=Abstract

TITLE:
Reactions at the Nonprecious Metal-Ceramic Interface during Porcelain Firing
(II) -- A Commercial Alloy Containing Higher Cr and Si--
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N. and Kobayashi,M.*
INSTITUTE:
Dental materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 8(5), 667-677, 1989
ABSTRACT:
To clarify the interface reaction between porcelain and a commercial Ni-Cr dental alloy (containing higher Cr and Si) during porcelain firing, electron probe microanalyzer (EPMA), X-ray diffraction and X-ray fluorescence analysis have been used to characterize the interface which has emerged by means of selective dissolution of the alloy caused by a bromine-methanol solution. At the early stage of firing, tin oxides (SnO2), contained in the porcelain powder, were reduced to Sn metal and the resultant reduction layer was about 10 ƒÊm in thickness from the interface. Although in the beginning of firing some Cr oxides were formed at the interface, with increasing retention time (within a few minutes) at 960C, extremely low oxygen partial pressure caused reduction of even such products.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2490211&dopt=Abstract

TITLE:
Reactions at the Nonprecious Metal-Ceramic Interface during Porcelainization
(I) -- Commercial Dental Alloy Containing Be --
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 7(4), 660-674, 1988
ABSTRACT:
To clarify the interface reaction between porcelain and a commercial Ni-Cr dental alloy (containing Be) during porcelainization, electron probe micro analyzer (EPMA) and X-ray diffraction method have been used to characterize the interface which emerged by selective dissolution of the alloy caused by the bromine-methanol solution. Elemental distribution maps across the reaction layer have been provided by alternating EPMA and etching the interface by 1 micron meter depth with Ar ion RF sputtering. At an early stage of porcelainization, a large amount of Ni oxide was generated. However, a long fusing interval resulted in the reduction of such a oxide and oxidation of Be became a dominant reaction. This is because porous porcelain particles change into airtight sintering glass and, as a result, oxygen partial pressure at the interface falls remarkably. Under this condition, oxidation depends upon the equilibrium dissociation pressure of each oxide rather than the alloy composition.

TITLE:
Microanalysis of Thin Oxide Film Formed by High-Temperature Oxidation of Commercial Ni-Cr Alloy containing Be for Metal-Porcelain Bonding
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., Shiokawa,N. and Kobayashi,M.*
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University and *EMX Laboratory, Niigata University
JOURNAL:
Dental Materials Journal, 7(1), 24-38, 1988
ABSTRACT:
Thin oxide films formed on commercial metal/porcelain Ni-Cr alloy containing Be, were studied by using the electron probe micro-analyzer (EPMA) with the glass lining technique and by the X-ray diffraction method with the Debye-Scherrer camera. Oxidation was restricted to form thin oxide films as follows; at 700C for 5 minutes in air, at 1,000C for 2 minutes in air, and at 1,000C for 40 minutes in vacuum (0.001Torr). In the case of oxidation in air, the major oxides were NiO and Cr2O3, and the ratios of Cr2O3 to NiO were 0.57 at 700C and 2.5 at 1,000C. For oxidation in vacuum, only BeO and BeCr2O4 were detected. In all cases, the fine structure of the oxide film was modified in correspondence with the substrate alloy phase. These structural data and morphological data are discussed with respect to the general oxidation theory.
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TITLE:
Microstructure of the Oxide Scale Formed on Ni-Cr Binary Alloys at High Temperature
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miayakawa,O., Nakano,S., Shiokawa,N., and Kobayashi,M.
INSTITUTE:

JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device 7:371-385, 1988
ABSTRACT:
Keyword: Ni-Cr alloy, High temperature oxidation, Multilayered structure, Oxygen gas diffusion
Four Ni-Cr binary alloys (5% Cr, 10% Cr, 18% Cr, and 20% Cr in weight) were oxidized at l,000 °C in air and the oxidation process was investigated by thermogravimetric measurement (TG), electron probe microanalysis (EPMA), and X-ray diffraction. For 5% Cr and 10% Cr alloys, 'breakaway' and multilayered structures occurred in spite of the constant temperature and 'pegs' of CrO3 developed at the innermost oxide layer. For 15% Cr and 20% Cr alloys, the inner oxide layer consisted of almost pure Cr2O3 but Deg formation was not observed. In the case of oxidation of pure Ni covered with thin vacuum-deposited Cr film, thin Cr2O3 layer (marker) existed at the intermediate position in the NiO scale, suggesting oxygen gas diffusion. In conclusion, the oxide scale feature (multilayred structure and peg formation) is due to the behavior of oxygen, such as inward diffusion.

TITLE:
Mechanism of Anisotropic Dimensional Changes in Wax Patterns Prepared by the Softened Wax Technique. III Influence of Additions on Recovery Phenomenon
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S. and Shiokawa,N.
INSTITUTE:
Dental Materials and Technology School of Dentistry, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 3(2), 227-236, 1984
ABSTRACT:
Binary mixtures added carnauba wax or dammar (up to 10% each) to paraffin (M.P.56-58C) were prepared. Cylindrical samples (25 mm in diameter, 25mm in height) were compressed uniaxially up to 50% at various temperature and, after that, behavior of plastic deformation, the degree of preferred orientation and the amount of recovery were investigated.
The degree of preferred orientation of above samples showed almost unchanged (about 80%). Addition of carnauba wax to the paraffin resulted in a large increase in the yield stress but a reduction of the recovery. The samples added dammer to the paraffin were similar in the plastic deformation but increased in recovery with an amount of its addition.
From these results, it is confirmed that the recovery of waxes (the paraffin and binary mixtures) originates from the rubber elasticity of molecules in the amorphous region.

TITLE:
A New Technique to Analyze the Thin Oxide Film Formed on the Nonprecious Metal for Metal-Ceramic Systems
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S., and Shiokawa,N.
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 2(2), 232-243, 1983
ABSTRACT:
In order to study the extreme thin oxide film formed on the nonprecious alloy for metal-porcelain systems at high temperature, new technique by means of EPMA has been developed. This is achieved by that after a glass plate sticked on the oxidized alloy, it is dipped in Bromine-methanol solution to dissolve the base metal selectively. By this process, only the oxide film attached on the glass plate can be obtained.
This new method, "glass lining technique," has following advantages.
(1) The elements composed of the oxide film, such as nickel and chromium, can be detected, being free from the alloy ingredients.
(2) The thickness of the extreme thin oxide film (ranging from a few hundreds to a few thousands angstrom) can be measured by counting the characteristic x-rays of silicon in the glass plate under the oxide film itself.
(3) Quantitative analysis of the oxide film can be easily performed.

TITLE:
Mechanism of Anisotropic Dimensional Changes in Wax Patterns Prepared by the Softened Wax Technique. II Determination of Paraffin Crystal Size
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S. and Shiokawa,N.
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University
JOURNAL:
Dental Materials Journal, 1(1), 55-66, 1982
ABSTRACT:
To estimate the paraffin crystal size, small-angle x-ray scattering has been conducted. For the specimen compressed uni-axially, a very long period (155A) has been found which is interpreted as a lamellar thickness. Moreover, this thickness remains unchanged during the recovery process.
"http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6964913&dopt=Abstract"

TITLE:
Basic Research on Setting Behavior of Phosphate-bonded Investment
(Part 1) Thermal Effects on Setting Time, Setting Expansion and Compressive Strength
LANGUAGE:
in JAPANESE with English Abstract
AUTHORS:
Watanabe,K., Okawa,S., Miykawa,O., Nakano,S. and Shiokawa,N.
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University
JOURNAL:
The Journal of the Japanese Society for Dental Materials and Device, 1(1), 39-46, 1982
ABSTRACT:
For the purpose of studying the effects of temperature during setting on the behavior of phosphate-bonded investment, following experiments have been conducted at the temperatures of 10, 20, 30 and 40C; measurements of normal setting expansion, compressive strength and chemical change of the binder by the x-ray diffraction technique. To avoid an increase in the sample temperature caused by the reaction heat, samples have been made as small as possible (10 mm in diameter and 15 mm in height). The ends of setting reaction are 200, 100, 35 and 7 minutes from the start of mix at 10, 20, 30 and 40C, respectively. At the temperatures of 10, 20 and 30C, initial and second contractions have been observed in the course of expansion curves. None of two contractions have been detected at 40C. The compressive strength is affected considerably by the setting temperature. In conclusion, the sample temperature during setting affects not only the rate of reaction but also certain properties, such as the setting expansion. Therefore, this factor must be always defined when some properties of this material are evaluated.

TITLE:
Mechanism of the Anisotropic Dimensional Change of the Wax Pattern Prepared by the Softened Wax Technique (1) Relationship between Recovery and Crystal Orientation
LANGUAGE:
ENGLISH
AUTHORS:
Watanabe,K.
INSTITUTE:
Dental Materials and Technology, School of Dentistry, Niigata University
JOURNAL:
Journal of the Japan Society for Dental Apparatus and Materials, 22(57), 63-96, 1981
ABSTRACT:
In order to obtain information on the behavior of wax pattern distortion and to reveal its mechanism, the following experiments have been conducted: measurements of fundamental properties including distribution of molecular weight, crystal structure, phase transition, and viscosity, and investigation of the crystal orientation and recovery phenomena. If the wax is deformed plastically at higher temperatures, transformation appears to be a smooth transition from an isotropic distribution of the crystal orientation to an arranged structure. In the case of uniaxial compression, the c-axes are rearranged parallel to the compressed direction and the b-axes and a-axes are randomly oriented in the plane normal to the c-axes. This preferred orientation is due to the crystal rotation. The degree of preferred orientation increases with the increase in compression ratio over all temperatures between 35C and 55C. Above 45C, the degree of orientation decreases with an increase in temperature despite the equal compression ratio. From this fact, the degree of orientation is associated with the crystallinity at deformation temperatures as well as the degree of deformation. The preferentially oriented specimen expands greatly in the direction parallel to the molecular chain axis and shrinks to a great extent in the direction perpendicular to the chain axis. This anisotropy is caused mainly by the recovery. Moreover, the extent of recovery is associated closely with the degree of the preferred orientation. The dimensional change due to the recovery is extraordinarily large (30 to 40%) in comparison with the normal thermal expansion from room temperature to 45C (approximately 1.2%). This large extent of recovery is explained by the rubber-like deformation in the amorphous region.
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