Search PubMed⌕ Search

Biomedical subjects

H Hamanaka

Publications and source records attributed to H Hamanaka.

At least 55 records · Page 3Linked to original sources
PubMed1991

Lowered Cu, Zn-superoxide dismutase activity in human malignant skin tumors.

We examined Cu, Zn-superoxide dismutase (SOD) activities of fifteen malignant skin tumors (four malignant melanomas, three squamous cell carcinomas, four Bowen's diseases, two basal cell epitheliomas, one sebaceous epithelioma, and one extramammary Paget's disease) and compared them with those in adjacent normal tissues of the same patients. Though there were some individual differences, all the SOD activities in tumor tissues were significantly lower than those in adjacent normal tissues of the same subjects. The average SOD activity in tumor tissues was 12.01 +/- 2.17 unit/mg protein, while that of normal tissues was 17.62 +/- 2.85. These findings agree with previous reports from various other organ tumors.

Aged↗
PubMed1991

Histochemical detection of burn-induced lipid peroxidation in sebaceous glands of rat skin.

Increased lipid peroxide levels both in skin and serum have been reported after cutaneous thermal injury. However, it still remains unclear where lipid peroxides are produced at the site of burned skin. In the present study, a histochemical method using cold Schiff's reagent was applied in order to detect the localization of lipid peroxide. Schiff positivity was detected in sebaceous glands, and the extent of positivity seemed to correlate with the serum lipid peroxide levels. These results may suggest that lipid peroxides produced in sebaceous glands after thermal injury enter the blood stream and are partially responsible for the elevated serum lipid peroxide levels.

Animals↗
PubMed1991

Development of sealed cup yoke type dental magnetic attachment.

The purpose of this study was to develop a small cup type yoke magnetic attachment sealed from oral fluid. The magnetic device forms a closed circuit between the magnet, yokes, and keeper. A 3.2 mm phi x 1.4 mm SmCO5 magnet was put into a cup yoke of 447J1 stainless steel and covered by 447J1 stainless steel disk yoke with a 316L stainless steel ring. To protect the magnet from corrosion, the connection was sealed by laser welding. The optimum dimensions were figured out by a finite element method. The performance of the magnetic attachment was investigated. As a result, a magnet device 4.4 mm in diameter and 2.1 mm in height was developed. The breakaway retention when the keeper touched it was 341 gf on average.

Dental Stress Analysis↗
PubMed1991

[Primary cardiac malignant mesenchymal tumor containing chondrosarcomatous component--a case report].

A case of 70 years old female bearing a primary cardiac tumor was presented. Mitral valve replacement and reconstruction of the interatrial septum were necessary because the tumor originated from the left atrial side of the interatrial septum and invaded the anterior mitral valve leaflet and around the annular area. Pathological examination of the resected specimens revealed mesenchymal tumor containing chondrosarcomatous component. The patient received radiation therapy (50 Gy) postoperatively and she resumed normal daily activity. Preoperative echocardiographic manifestations were of proved benefit in the diagnosis of malignant cardiac tumor and a proper therapeutic strategy could be chosen.

Aged↗
PubMed1990

Photoprotective effect of topically applied superoxide dismutase on sunburn reaction in comparison with sunscreen.

Photoprotective effect of topically applied superoxide dismutase (SOD) to guinea pig skin was compared with a commercially available sunscreen agent after a single exposure to UVB. While cutaneous SOD activity was remarkably decrease in non-treated control animals, both topical SOD and sunscreen agent significantly reduced the decrease in skin SOD activity after UVB irradiation. However, only the sunscreen agent successfully reduced erythema reaction 24h after irradiation but topical SOD failed. These findings suggest that topical SOD protects skin from photo-oxidative damage without affecting erythema response, and thus, from a practical standpoint, sunscreen agents, when compared with topical antioxidants, seem better at present for daily photoprotection.

Administration, Topical↗
PubMed1989

Dental casting of titanium and Ni-Ti alloys by a new casting machine.

The purpose of this study was to develop a new casting machine for titanium and Ni-Ti alloys. Properties of cast pure titanium and Ni-Ti alloys were studied by means of the tensile and casting tests. As gas in the mold was removed by the mold being heated under a high vacuum, the reaction between the molten metal and the mold decreased. The new control system and the two types of crucibles developed proved very useful for prevention of internal macro-defects in castings and for improvement of castability. Mechanical properties and castability of pure titanium were improved. Ni-Ti alloys could be cast without loss of their shape-memory effect or super-elasticity characteristics. The new casting machine is thought to be promising for the casting of titanium and Ni-Ti alloys. Furthermore, we can cast these alloys using conventional techniques and investments.

Dental Alloys↗
PubMed1989

[Evaluation of super-elasticity characteristics of orthodontic Ni-Ti alloy wire].

Mechanical properties of orthodontic Ni-Ti alloy wires, especially their super-elasticity characteristics, were investigated in order to use them effectively in the clinics. In this study, twenty commercial orthodontic Ni-Ti wires were tested and two parameters were devised for the load-deflection curve and introduced to evaluate the practical mechanical properties, one being the "super-elastic index: SEI" for super-elasticity, and the other being the "E-load" for the load in the super-elastic region. There was a "flat area" in the load-deflection curve of the super-elastic type of Ni-Ti alloy wires, whose SEI was above seventy and a continuous force could be used through the wide range of deflection. The load of the work-hardened type of Ni-Ti wires, SEI below thirty, was nearly proportional to the deflection. And the middle type showed intermediate properties of the two. The E-load values of the super-elastic type wires are thought to indicate the load level in the super-elastic region. The quantitative evaluation of the super-elasticity characteristics of the orthodontic Ni-Ti wires became possible by the introduction of these parameters.

Dental Alloys↗
PubMed1989

[Retention of Pt-Co magnet for dental prosthesis].

Though Pt-Co magnet is inferior to rare-earth magnet in magnetic properties, the magnet is much superior to the corrosional resistances in oral fluids. The purpose of this investigation was to determined the retentive characteristics of Pt-Co magnet. The break away force between the magnet and XM27 stainless steel keeper were measured. The retention of phi 4x 1.5 mm Pt-Co magnet was 49 g. This retention could be increased to 172 g by using stainless steel cup type yoke. These retention were rather small, but if 3 or more couples of attachments or larger Pt-Co magnet attachment were fixed in denture, the retention level approach that of clasp or mechanical precision attachments.

Cobalt↗
PubMed1989

[Sandwich type dental magnetic devices of Nd-Fe-B magnet and permendur].

Nd-Fe-B magnets have a very high maximum energy product (BH max), which is defined as the attractive strength between a magnet and opposing magnetic materials. Permendur (Fe-49 Co-2 V) has the greatest magnetic saturation (Bs), which makes it strongly magnetized. If magnetic retainers were made with Nd-Fe-B magnets and a permendur yoke, they would be small and have strong retention. The purpose of this investigation was to develop small dental magnetic devices with Nd-Fe-B magnets and permendur yokes. The magnetic devices form sandwich-type magnetic circuits with magnetic stainless steel keepers. A 4 x 3 x 2 mm rectangular prism Nd-Fe-B magnet was used. The magnet was sandwitched between the semi-columnar yokes. To protect the magnet from corrosion, the devices were encapsulated with 304 stainless steel by silver brazing and adhesion bonding of a stainless steel tube and foil. The optimum cross-sectional area of the yoke was determined experimentally. The dimensions of the devices were phi 5 x 3.5 mm for 4 x 3 x 2 magnet. The breakaway retention for a keeper of magnetic stainless steel (Type XM 27) was 852 g on average. This breakaway retention is sufficient for dental prosthetic applications.

Beryllium↗
PubMed1989

[Superplastic forming of titanium alloy denture base].

Ti-6Al-4V alloy has both excellent biocompatibility and superior mechanical properties. This Ti-6Al-4V can be deformed greatly and easily at the superplastic temperature of 800 degrees C to 900 degrees C. The superplastic forming of Ti-6Al-4V was made to apply to fabrication of denture base. Almost the same procedure as for dental casting mold was employed in producing the superplastic forming die by the improved phosphate bonded investment. In the pressure vessel of heat resistant alloy, Ti-6Al-4V plate was formed superplastically on the die by argon gas pressure at 850 degrees C. The fit of superplactic forming Ti-6Al-4V denture base was better than that of casting Co-Cr alloy denture bases. The Ti-6Al-4V alloy might react a little with the die. Because micro Vikers hardness of the cross-section did not go up too much near the surfaces. Even just after being formed, the surfaces were much smoother than that of Co-Cr alloy casting. The tensile strength and yield strength of superplastic forming Ti-6Al-4V were higher than those of Co-Cr castings. The elongation was about 10%. These results show that superplastic forming of Ti-6Al-4V would be suitable for a denture base.

Dental Alloys↗
PubMed1989

[Mechanical properties and phase transformation of super-elastic Ni-Ti alloy wires. Part 1: Relation between super-elasticity and phase transformation].

The relationship between mechanical properties and thermal behavior of super-elastic Ni-Ti alloy orthodontic wires was investigated in order to use them effectively in clinics. Three types of super-elastic Ni-Ti alloy orthodontic wires, SENTALLOY-BLUE(SB), YELLOW(SY) and RED(SR), were used. Two parameters were introduced from the load-deflection curves in three point bending test to evaluate their mechanical properties. One was the super-elastic index (SEI) for super-elasticity, and the other was the E-load for the load in the super-elastic region. Their thermal behavior in the course of the transformation analyzed with DSC, and compared with the mechanical properties. The specimens heat-treated at 500 degrees C for 30 min were also examined. The differences in mechanical properties of the super-elastic Ni-Ti alloy orthodontic wires used in this study were thought to be more affected by the height of the thermic peak and the form of the DSC curves than the transformation temperature. The higher the thermic peak, the higher tended to be the SEI and the lower E-load. To the contrary, the lower thermic peak, the higher was the E-load and the lower was the SEI, and the continuous force could not be achieved. The remaining work-hardened structure was thought to influence these differences.

Dental Alloys↗
PubMed1989

[Mechanical properties and phase transformation of super-elastic Ni-Ti alloy wires. Part 2: Changes of properties through heat treatment].

Three types of super-elastic Ni-Ti alloy orthodontic wires, SENTALLOY-BLUE (SB), YELLOW (SY) and RED (SR), on the change of properties were studied especially the reversible change of the load level, using three point bending test and DSC. The heat treatment at 440 degrees C caused the largest reduction in mechanical properties of SB and SY, and the 400 degrees C treatment did that of SR. The load level of SR was less changeable than those of SB and SY by the difference of heat treatment temperature. Mechanical properties of SY were almost reversible by the alternate heat treatment at 440 degrees C and 510 degrees C. Then the 440 degrees C-heat treatment increased the transformation temperature, and the 510 degrees C-heat treatment decreased them. The variation of the mechanical properties completely corresponded to the change in transformation temperature. The variation appears to result from some internal structure changes. Changes in mechanical properties are observed by heat treatment at 360, 400 and 480 degrees C, but the reversibilities were not so clear. The change of the properties of super-elastic wires are influenced by the kind of wire and the heat treatment condition. The reversible change in the mechanical properties seems to have many advantages over super-elastic Ni-Ti alloy orthodontic wires.

Dental Alloys↗
PubMed1986

The super-elastic property of the Japanese NiTi alloy wire for use in orthodontics.

A new Japanese nickel-titanium (NiTi) alloy wire was developed by the Furukawa Electric Co., Ltd. of Japan. This wire was subjected to uniaxial tensile testing and a specially designed three-point bending test to determine the wire stiffness, and to evaluate spring-back, shape memory, and super-elasticity. The Japanese NiTi wire exhibited an unusual property termed "super-elasticity," which no other orthodontic wire has shown. This phenomenon was researched thoroughly. The wire delivered a constant force over an extended portion of the deactivation range. Among all the wires compared, Japanese NiTi alloy wire was the least likely to undergo permanent deformation during activation. The new alloy exhibited a specific stress-strain curve unlike those of the other tested materials. Stress remained nearly constant despite the strain change within a specific range. This unique feature is the manifestation of so-called super-elasticity. Heat treatment enabled the load magnitude at which super-elasticity is reflected to be influenced and controlled by both temperature and time. A unique and useful process was also developed so that an arch wire delivering various magnitudes of force for a given activation could be fabricated from the wire of the same diameter. The clinical application of wires of this new alloy should be more likely to generate a physiologic tooth movement because of the relatively constant force delivered for a long period of time during the deactivation of the wire. Japanese NiTi alloy should be considered an important material addition to clinical orthodontic metallurgy.

Chromium Alloys↗