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Biomedical subjects

H Shintani

Publications and source records attributed to H Shintani.

At least 91 records · Page 5Linked to original sources
PubMed1990

Timing of operation for aortic regurgitation: relation to postoperative contractile state.

With angiography and pressure measurement, we determined left ventricular volume, wall stress, and systolic performance in 30 patients with aortic regurgitation before and after successful aortic valve replacement. End-systolic wall stress was greatly elevated preoperatively and decreased to normal postoperatively. Systolic pump performance assessed as ejection phase indexes was severely depressed preoperatively and improved to normal or near-normal postoperatively in most patients. The ratio of end-systolic wall stress to end-systolic volume index (ESS/ESVI), an index of myocardial contractility, was greatly decreased before operation. Postoperatively, the ratio increased in all patients, becoming normal in 12 of the 13 patients who had a preoperative ESS/ESVI of 2.9 or greater. However, 15 of 17 patients in whom the ESS/ESVI ratio was less than 2.9 still had subnormal ratios, which indicates the presence of irreversible contractile dysfunction. Stepwise multivariate analysis showed that preoperative ESS/ESVI was the only independent discriminator of postoperative normalization of the contractile function as assessed by ESS/ESVI. After aortic valve replacement, myocardial contractile state does not return to normal in a considerable number of patients. It is important to offer aortic valve replacement for aortic regurgitation before the chance for a good functional result is lost. The ESS/ESVI ratio may be a useful index in determining the timing of operation in patients with aortic regurgitation.

Adult↗
PubMed1990

A medicated polycarboxylate cement to prevent complications in composite resin therapy.

Preparative treatment is the preferred method to protect the dentin and pulp from complications in composite resin therapy. This study investigated the in vivo effects of the polycarboxylate cement containing zinc fluoride and tannic acid in composite resin restorations. Scanning electron micrographs established that the composite resin failed to contact the axial wall. The gaps varied from 10 to 60 microns. However, this polycarboxylate cement was shown to provide excellent adaptation to dentin when used as a base and its chemical adhesion allowed it to make close contact with the unetched dentin. The newly developed electron probe x-ray microanalyzer revealed that the in vivo penetration of fluoride and zinc occurred through the dentinal tubules. When this polycarboxylate cement was used, the orifices of dentinal tubules were partially occluded, possibly with the smear layer fixed by tannic acid. In addition, by releasing the components, this polycarboxylate cement adds acid resistance to dentin and increases the resistance of dentin collagen to proteolytic enzymes. As such this polycarboxylate cement offers advantages as a base to composite resin therapy.

Adolescent↗
PubMed1990

[The effect of ammonium fluoride solution at various concentrations on enamel].

The fluoride concentrations of ammonium fluoride solution (NH4F,pH 4.4), which has the same effect on enamel powder as conventional APF solution, were studied. Human enamel powder (200 mesh passed) was treated with solutions of NH4F (1,000 ppmF-, 3,000 ppmF-, 5,000 ppmF-, 7,000 ppmF-, 9,000 ppmF-, pH 4.4) and APF (9,000 ppmF-, pH 3.4) for 5 min. at 37 degrees C. Some of the specimen was washed with 1MKOH solution for 48 hours. Fluoride uptake by enamel powder was analyzed by means of chemical analysis and reaction products identified using X-ray diffractometry. The fluoride uptake of 5,000 ppmF- of NH4F-treated enamel was the same as that of APF-treated enamel. X-ray diffractometry showed that CaF2 was formed in the experimental groups. CaF2 with high crystallinity was formed in the NH4F-treated enamel, and the peak height of X-ray diffraction pattern of CaF2 in 3,000 ppmF- of NH4F-treated enamel was the same as that of APF-treated enamel. In conclusion, the ammonium fluoride solution of 3,000-5,000 ppmF- had a similar effect on enamel powder as conventional APF solution.

Acidulated Phosphate Fluoride↗
PubMed1989

Clinical evaluation of two posterior composite resins retained with bonding agents.

Two hundred thirteen carious cavities were restored with two brands of chemically adhesive posterior composite resins by totally etching both the enamel and dentin walls after removing only the caries detector-stainable tissue and with no mechanical retention form in the cavity preparation. Most cavities were extensive, involving more than two surfaces in 74%. The dentin floor was not covered with cement although a spot lining was placed when the cavity was deep. All restorations were examined, usually after 4 years, by photographs and scanning electron microscope observation of replicas, and by criteria established by the U.S. Public Health Service. The materials and the technique proved to be clinically useful.

Acid Etching, Dental↗
PubMed1989

In vitro color change of composite-based resins.

The adsorption of staining materials to resin restoratives was considered to be influenced by the physico-chemical properties of the resin-based monomers. To study the effects of the surface characteristics of resins on staining, we prepared five visible-light-cured experimental resins without fillers. Staining of these resins was colorimetrically measured. The staining solutions used were the Oil Orange and the Food Red 3 solutions. With the Oil Orange solution, the materials with higher hydrophobicity showed higher staining. With the Food Red 3 solution, the materials with higher water sorption showed higher staining.

Color↗
PubMed1989

Studies of machinable ceramics for dental applications. 1. Color analysis.

Machinable ceramics that can be cut and even lathed have recently been developed in industry. As a first step in evaluating the feasibility of such ceramics in dentistry, eight machinable ceramics were examined for color using the Vita shade guide and a chroma-meter reflectance instrument. We discovered that the studied machinable ceramics varied significantly from the Vita shade guide by the color difference vector, delta E. These machinable ceramics appeared very white and strongly opaque due to their high brightness (L*) values. For intra-oral applications, we expect that L* values of machinable ceramics will be reduced by modification of their microstructures, including their matrix and dispersed phases, while their excellent machinability due to the cleavage of dispersed crystals should be retained.

Color↗
PubMed1989

[Evaluation of plasma PIVKA-II as a new marker for hepatocellular carcinoma].

We have measured the plasma PIVKA-II levels in 188 cases of various liver disease with HCC and malignant diseases in other organs by an EIA, using a monoclonal antibody (E-1023 kit, Eisai), and also have measured the plasma vitamin K levels in cases of HCC and cholestasis by an HPLC. Plasma PIVKA-II was detected in many cases of HCC (67%, 35 of 52 cases) and cholestasis (60%, 6 of 10 cases). In contrast, the positivities of PIVKA-II in the other diseases including benign liver diseases were very low. Combination assays of PIVKA-II and vitamin K revealed that PIVKA-II correlates with vitamin K in cholestasis but not in HCC, suggesting that PIVKA-II in HCC does not depend on a systemic deficiency of vitamin K. From these results, it was concluded that PIVKA-II is a reliable marker which can reflect the clinical course of HCC.

Adult↗
PubMed1989

[Cohort study on cariostatic effect of 100ppmF- fluoride mouthrinsing].

The cariostatic effect of fluoride mouthrinsing with dilute fluoride solution in the school dental health programs was examined. The subjects were 138 children (75 of boys and 63 of girls) who carried out fluoride mouthrinsing with solution of 100 ppmF- for 6 years and 105 children (65 of boys and 40 of girls) who had no fluoride mouthrinsing were analysed by cohort study from 1983 to 1989. The cariostatic effect was evaluated by DMFT index and DMF rate for each tooth type in each erupted school grade. The increment of DMFT index was less than that of the control group. There was a clear cariostatic effect with the advance in the school grade. DMF rate for each tooth type of 1 in 2nd grade and 2 in 3rd grade students showed a statistically significant difference. Both that of upper and lower first molars in 1st and 2nd grade also showed the same result as that of upper incisors. In conclusion, a high cariostatic effect was obtained by introducing the use of fluoride mouthrinsing with a solution of 100ppmF- to the school dental health program, and the observation of DMF rate for each tooth type classified with each erupted school grade was a useful method to evaluate the cariostatic effect of fluoride mouthrinsing.

Child↗
PubMed1988

Necrotizing effect of ethanedimethanesulfonate on spontaneously occurring Leydig cell tumors in old F344 rats.

Thirty 18-month-old male F344/DuCrj rats were divided into the following groups: 10 untreated controls; eight vehicle-injected controls; and 12 ethanedimethanesulfonate (EDS)-injected rats. Untreated controls were killed immediately to check for testicular tumor incidence. In rats of the test group, a 75-mg/kg dose of EDS dissolved in dimethyl sulfoxide:water (1:3) was injected i.p. At intervals of 1, 2, 3, and 10 days after injection, two vehicle-injected control rats and three EDS-injected rats were sacrificed, and the testes were fixed by vascular perfusion. The midsagittal sections of all the fixed testes were examined to determine the incidence of macroscopic Leydig cell tumors, and some tumor tissues of the injection-treated groups were also investigated ultrastructurally. In 28 of 30 animals, a total of 78 Leydig cell tumors could be distinguished. Extensive and severe necrotic alterations accompanying fresh, multiple hemorrhages in early stages and reparative changes in later stages could be observed in a total of 78% of the 32 tumors examined from the EDS-injected group. The tumor cells exhibited ultrastructurally degenerative changes such as chromatin condensation and cytoplasmic vacuolation from 1 day after EDS injection. Therefore, EDS may be a necrotic agent for rat Leydig cell tumor.

Animals↗
PubMed1988

Adherence of streptococci to surface-modified glass.

Four types of surface-modified glass were prepared. Aminopropyl glass was prepared by alkylsilylation of glass slides with gamma-aminopropyltriethoxysilane. This glass carries primary amino groups which may be protonated at pH 7.2. Owing to the presence of both positively charged ions and hydrophobic ethoxyl groups, the glass is considered to be amphipathic. Three other types of surface-modified glass slides were prepared from aminopropyl glass by forming Schiff's bases with three aldehydes: glucose, glyoxylic acid and hexanal. The aldehyde-treated slides were subsequently reduced using sodium borohydride. Thus, the surface of the glass was rendered hydrophilic, ampholytic or hydrophobic, respectively. The adherence of two Streptococcus sanguis strains and two Streptococcus mutans strains to the surface-modified glass slides was studied. Different strains showed differences in adherence to these slides depending on their physico-chemical surface properties. For S. sanguis ATCC 10556, hydrophobic bonds seemed to be most important, while in S. mutans OMZ 176, ionic interactions made the highest contribution to adhesion. Hydrogen bonds seemed to contribute least to adherence.

Bacterial Adhesion↗
PubMed1988

Streptococcal adherence on various restorative materials.

The adherence of Streptococcus sanguis ATCC 10556, S. sanguis ATCC 10557, S. mutans Ingbritt, and S. mutans OMZ 176 to the surfaces of composite resins, amalgam alloys, and a Au-Ag-Pd alloy was measured. Adhesion was correlated with values for hydrophobicity and zeta-potential of the bacteria and the restorative materials. The hydrophobicity of the restoratives showed a positive correlation between the numbers of adherent S. sanguis cells, suggesting that hydrophobic interactions are important for the adherence of this bacterial species. In contrast, the numbers of adherent S. mutans cells showed a positive correlation with the zeta-potential of the restoratives, suggesting that electrostatic interactions are important in adherence of this bacterium.

Bacterial Adhesion↗