Kunihiro Hisatsune

Buccal hemangioma with phleboliths: Report of two cases

Two cases of buccal hemangioma with phleboliths were reported. Angiography, angioxerography, and computerized tomography were carried out before the procedures were planned. One patient was treated by means of surgical excision of the tumor after ligation of the left external carotid artery. The second patient was treated by means of surgical excision alone. Histologic examinations suggested that the thrombi in the blood vessels of hemangiomas might become the core of the phleboliths. Analysis of the phleboliths by means of x-ray diffraction and infrared spectrometry confirmed calcium phosphate and calcium carbonate as the main components of the phleboliths.

Spinodal ordering in the equiatomic AuCu alloy

Abstract To identify spinodal ordering in AuCu alloys, electron microscopy and electron and X-ray diffraction examinations were employed on the equiatomic composition of AuCu alloy using direct ageing. The spinodal ordering temperature T′s and the coherent phase boundary T s were determined to be 630 and 648 K respectively. Three distinguishable phase transition mechanisms were found. (1) The ordering proceeds at grain boundaries by a heterogeneous nucleation mechanism after showing an incubation period at a temperature between the transition temperatures T c and T′c. (2) The ordering is induced in the grain interior by a homogeneous nucleation mechanism between T′c and T c. (3) The spinodal ordering is brought about below T s. The microstructure induced by the spinodal ordering is characterized by the tweed structure. The direct-ageing method is effective in distinguishing the ordering processes with or without an incubation period, and in eliminating confusion in microstructures by the unavoidable order...

In vitro corrosion behavior of cast iron–platinum magnetic alloys

OBJECTIVE The objective of this study was to investigate the corrosion resistance of cast Fe-Pt alloys of varying compositions for use as attachment keepers and to make a comparison with the corrosion resistance of magnetic stainless steel. METHODS The corrosion behavior of cast Fe-Pt alloy keepers (Fe-40 at%Pt, Fe-38 at%Pt, Fe-37 at%Pt and Fe-36 at%Pt) was evaluated by means of an immersion test and an anodic polarization test. The solutions used were a 1.0% lactic acid aqueous solution (pH=2.3) (10 ml) and 0.9% NaCl solution (pH=7.3) (10 ml). As a control, the corrosion resistance of a magnetic stainless steel keeper (SUS 447J1: HICOREX) was also measured. RESULTS Chromium and platinum ions were not detected in either the 1.0% lactic acid or 0.9% NaCl solutions. The only released ions detected were the Fe ions in the 1.0% lactic acid solution. The amounts of Fe ions released from the Fe-40 at%Pt and Fe-38 at%Pt alloys were significantly (p<0.05) lower than from the Fe-37at%Pt, Fe-36 at%Pt and SUS 447J1 alloys. In the anodic polarization test, the potentials at the beginning of passivation for the four Fe-Pt alloys were higher than for the SUS 447J1 alloy in both solutions. SIGNIFICANCE The Fe-Pt alloys, especially the alloys with higher Pt percentages (Fe-40 and 38 at%Pt), indicated a high corrosion resistance compared to the magnetic stainless steel keeper. A reduction in the Pt percentage may decrease the corrosion resistance in the oral environment.

Structural aspects of AuCu I or AuCu II and a cuboidal block configuration of f.c.c. disordered phase in AuCuPt and AuCuAg pseudobinary alloys

Abstract A crystallographic analysis of the relative orientation of the microstructure of the two-phase (AuCu I or AuCu II) alloy coexisting with cuboidal block configurations of disordered f.c.c. phase was performed by means of transmission electron microscopy (TEM) and high-resolution electron microscopy complemented with selected area electron diffraction (SAED) examinations in (AuCu)1−X−PtX (X = 0.0135, 0.0248, 0.0469 and 0.0692 in atomic ratio), AuCu9 at.% Ag and AuCu14 at.% Ag alloys. In (AuCu)1−X−PtX alloys, a characteristics checkerboard-like microstructure which was composed of cuboidal blocks of disordered f.c.c. enclosed by two parallelogram-shaped orientation variants of AuCu IX and AuCu IY ordered regions without twin relation was observed, although the SAED pattern showed twinning. Evidence for a twin relation was found in small ordered regions observed in the cuboidal blocks unavoidably during quenching from an ageing temperature to ice brine. The cuboidal block was enclosed by four parallelogram-shaped AuCu I regions. The orientation relationship was deduced as (001)AuCu I//{100}α2 and the interface was defined as the {102}AuCu I. The microstructure consisted of the cuboidal block of a silver-rich f.c.c. α2 phase surrounded by three different orientation variants of the AuCu II ordered regions in which two of three variants had twin relation in AuCu9 at.% Ag and AuCu14 at.% Ag alloys. The orientation relationship was deduced as (001)AuCu II//{100}α2 and the interface was defined as the (001)AuCu II. The formation sequence of the checkerboard-like microstructure in (AuCu)1−X−PtX alloys was also analyzed using dark-field images in conventional TEM and SAED observations.

Age-hardening behavior in a palladium-base dental porcelain-fused alloy

Abstract Age hardening in a Palladium-base porcelain-fused alloy was investigated by hardness tests, x-ray diffraction, scanning, and transmission electron microscopy. In the early stages of aging, a metastable ordered phase with a face-centered tetragonal structure based on Pd 3 In was formed within the grains. Hardening was due to coherency strain between the metastable structure and the matrix with a face-centered cubic structure. In the later stages, a lamellar structure, consisting of a stable ordered phase with a face-centered tetragonal structure based on Pd 3 In and a stable phase with a face-centered cubic structure, grew from the grain boundaries. Finally, the lamellae covered the whole grain and resulted in softening.

Ordering behaviors and age-hardening in experimental AuCu-Zn pseudobinary alloys for dental applications

Age-hardening mechanisms and related ordering behaviors of the experimental (AuCu)(1-x)Zn(x) alloys with x < or = 0.2 were investigated for dental applications. The addition of Zn to equiatomic AuCu greatly increased the age-hardening rate and delayed overaging. It was suggested that the quenched-in excess vacancies were greatly related to the age-hardening rate in the AuCu-Zn pseudobinary alloys. In these alloys, the hardness became maximum during the very initial stage of ordering, and with the development of ordered phase, the hardness began to decrease. Transmission electron microscopy revealed that the age-hardening of AuCu-Zn pseudobinary alloys is caused by lattice distortion that occurred during the very early stage of atomic ordering. The addition of Zn to AuCu effectively increased the density of antiphase boundaries per unit volume of the AuCu II superstructure. This is suggested to be the main cause for the retardation of the overaging in the alloys containing Zn of 5 at% or more. This pronounced effect of Zn addition to AuCu alloy on its age-hardening characteristics may be advantageous for obtaining stable mechanical properties of dental casting gold alloys.

Attractive force of castable iron-platinum magnetic alloys.

OBJECTIVE The objective of this study was to examine the attractive force of cast Fe-Pt alloys of varying compositions to dental iron-neodymium-boron magnets. METHODS Ingots of Fe-40 at%Pt, Fe-38 at%Pt, Fe-37 at%Pt and Fe-36 at%Pt alloys were cast in pattern molds for dental magnetic attachment keepers. The attractive forces of the cast Fe-Pt alloy keepers and magnetic stainless steel keepers to dental Fe(14)Nd(2)B magnets (MAGFIT and HICOREX) were measured and statistically evaluated. The saturation magnetization of each Fe-Pt alloy was determined by recording the hysteresis loop using a vibrating sample magnetometer under a magnetic field of 1.6 MA/m. RESULTS Decreasing the Pt percentage increased the saturation magnetization value and resulted in an increase of the attractive force to each magnet. There was no statistical difference (p>0.05) in attractive force between the Fe-36 at%Pt alloy specimens and the stainless steel keepers for both magnets. A definite correlation between Pt percentage and the value of saturation magnetization was also found (r(2)=-1.000). SIGNIFICANCE The Fe-Pt alloys with less than Fe-39.5 at%Pt produced high saturation magnetization values and great attractive force to the magnet, and thus, they have the potential to serve as magnetic attachment keepers. Of the Fe-Pt alloys tested, Fe-36 at%Pt seemed to be the best composition for making magnetic attachment keepers.

Age-hardening reactions and microstructures of a dental gold alloy with palladium and platinum

The age-hardening reactions and microstructures of a dental casting gold alloy with some palladium and platinum were investigated by means of hardness tests, X-ray diffractometry, electrical resistivity measurements, and scanning and transmission electron microscopy. Ageing reactions during isothermal annealing were completed by two stages. The first stage corresponded to the formation of a metastable CuAu I phase within grains, and the second stage to a cellular reaction at grain boundaries. The former contributed to the hardening and the latter to the softening. An activation energy of 128 kJ mol−1 for hardening was obtained. Two types of cell growth were observed and could be distinguished in terms of the homologous temperature.

Aging Reactions in a Low Gold, White Dental Alloy

Aging behavior of a low gold, white dental alloy was investigated by electrical resistivity measurements, X-ray diffraction, and electron microscopy. It was characterized by both grain interior and grain boundary reactions. The coexistence of AuCu-I and CuPd in dental alloys was first confirmed.

Optical Properties of Au-Pt and Au-Pt-In Alloys

The effects of platinum addition to gold and indium addition to a gold-platinum alloy on their optical properties were investigated using a computer-controlled spectrophotometer. Spectral reflectance data from a polished sample for the incident CIE standard illuminant D65 was collected as a function of the wavelength at 10 nm intervals from 360 to 740 nm. Three coordinates,L* (lightness),a* (red-green),b* (yellow-blue), in the CIE 1976L*a*b* colour space, were determined to quantify the colour of experimental binary Au-Pt and ternary Au-Pt-In alloys. p ]The pronounced step near 520 nm (approximately 2.4 eV) in the spectral reflectance-wavelength curve for pure gold, which is responsible for the rich yellow colour of gold, became less pronounced with the addition of platinum. The decoloring effect of platinum was found to be due to this phenomenon. The addition of indium of up to ca 4 at% to a Au-10 at% Pt alloy increased both chromaticity indices, ie,a* andb* values, giving a gold tinge to the alloy: this effect was brought about by both the slight increase in reflectance in the long-wavelength range and the slight decrease in reflectance in the short-wavelength range of the visible spectrum.