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Biomedical subjects

K Wakasa

Publications and source records attributed to K Wakasa.

At least 109 records · Page 6Linked to original sources
PubMed1995

Hardness and fracture toughness of four commercial visible light-cured composite resin veneering materials.

Four commercial visible light (VL)-cured composite resin veneering materials with a dentine shade were examined for their Knoop hardness and fracture toughness. Composite specimens were classified into three groups. The first group was cured by VL only, the second group was cured by VL and post-cured by VL and the third group was cured by VL and post-cured by heat. It became evident that one composite containing four-functional urethane monomer had both hardness and fracture toughness greater than those of the other three composites containing two-functional urethane monomer. The filler content (vol%) in the composite tended to be linearly proportional to both hardness and fracture toughness. Post-curing by VL and heat were proven to effectively increase both hardness and fracture toughness of once light-cured composites. These results suggest that the clinical performance (e.g. wear resistance and colour stability) of VL-cured composite resin veneering materials might be improved with the aid of post-curing.

Composite Resins↗
PubMed1995

Thermal behaviour of casting investment during setting.

The aim of this study was to examine the thermal reactions of silica-sol liquids for mixing investment powders using differential thermal analysis (DTA) and also the setting behaviour of the mixed powders using differential scanning calorimetry (DSC). The silica-sol liquids showed the appearance of vapourization (around 100 degrees C as a peak temperature) and combustion (200-300 degrees C) in DTA measurement. Mixed silica-sol investment exhibited the setting behaviour with an exotherm in the DSC measurement representing that greater peak time, setting time and heat in mixed investment than with gypsum-bonded investment.

1-Propanol↗
PubMed1995

Calculation models for average stress and plastic deformation zone size of bonding area in dentine bonding systems.

Average stress during shear bond testing, and deformation behaviour during nano-indentation testing were calculated for the bonding area as a bonding site for copolymerization with resin composite in dentine bonding systems. First average stress was calculated in the bonding area between bovine dentine and composite resin. Secondly, the plastic deformation zone size was calculated using an elastic/plastic deformation zone model after a nano-indentation test. The result clearly showed that average stress depended upon the elasticity of the bonding area, the elasticity value ratio of the composite resin-to-bonding area, and interfacial stress between the dentine and the adhesive resin. In this bonding area, the elasticity/hardness ratio changed depending on the thickness of the bonding area as well as the plastic deformation zone size (b), expressed as a (b/2a)-value (indented triangular length (2a) at nano-indentation test) expanded with increasing the elasticity value.

Animals↗
PubMed1994

Isolation and characterization of 21 novel expressed DNA sequences from the distal region of human chromosome 4p.

We have established an approach to the isolation of expressed DNA sequences from a defined region of the human chromosome. The method relies on the direct screening of cDNA libraries using pooled single-copy microclones generated by a laser chromosome micro-dissection in conjunction with a single unique primer polymerase chain reaction (SUP-PCR) procedure. We applied this method to the distal region of human chromosome 4p (4p15-4pter), which contains the Huntington disease (HD) and the Wolf-Hirschhorn syndrome (WHS) loci. Twenty-one nonoverlapping and region-specific cDNA clones encoding novel genes were isolated in this manner. Ten of 21 clones were subregionally assigned to 4p16.1-4pter, and the remainder mapped to the region proximal to 4p16.1. Northern blot and reverse transcription followed by the PCR (RT-PCR) analysis revealed that 16 of these 21 clones detected transcripts in total RNA from human tissues. Our method is applicable to other chromosomal regions and is a powerful approach to the isolation of region-specific cDNA clones.

Base Sequence↗
PubMed1994

Isolation of expressed sequences encoded by the human Xq terminal portion using microclone probes generated by laser microdissection.

The genes that cause a variety of neurologic and neuromuscular disorders have been mapped to the distal region of Xq. In an effort to isolate genes from this area, a regional genomic library of the distal 30% of Xq was constructed from a single metaphase spread by means of laser microdissection and single unique primer-polymerase chain reaction. Using pooled probes of 1000 clones from the genomic library, human brain cDNA libraries were screened for expressed sequences encoded by this region. From the 250,000 cDNA clones screened so far, 10 nonoverlapping sequences that mapped back to the target portion were isolated. The complete nucleotide sequences of these cDNA clones have been determined. Analysis of the sequences indicates that none has significant similarity to previously characterized primate genes. One sequence mapping to Xq27.3-qter contained an open reading frame of 281 amino acids and was expressed in every tissue tested. This gene, as well as others isolated in this manner, may prove to be a candidate gene for heritable disorders mapping to this region.

Amino Acid Sequence↗
PubMed1994

Primary leiomyosarcoma or leiomyoma of the pubic bone? A case report.

We report a case of what appeared to be a primary leiomyosarcoma of the left pubic bone of a female aged 23 years. Forty-eight cases of the tumour have been recorded in the literature since 1944, only two of which were in the pelvis. The tumour in our patient was treated by curettage and there was no recurrence in the following 3 years. The tumour cells showed only mild cellular atypism and 2 to 3 mitoses per 10 high-power fields. These finding suggest that the tumour might be an extremely rare leiomyoma of bone.

Adult↗
PubMed1994

Solitary glomus tumour with mucinous degeneration.

Four cases of solitary glomus tumour are reported, three of the angiomatous type, and one of the epitheliomatous type. In all cases, mucinous degeneration was seen, the extent of which correlated with the number of glomus cells.

Adult↗
PubMed1993

Effects of post-curing by heat on the mechanical properties of visible-light cured inlay composites.

The aim of this study was to evaluate the effects of post-curing by heat on the mechanical properties of visible-light (V-L) cured three inlay composites and three posterior filling composites. One group was only photo-cured according to the manufacturers' recommended methods, while the other group was heat-treated at 100 degrees C for 15 min following initial cure by V-L. Knoop hardness, diametral tensile strength and compressive strength were measured to evaluate the mechanical properties. Cure performance was checked out by the solvent immersion test. Upon secondary-curing by heat, it was confirmed that the mechanical properties of the composites were increased moderately and the cure performance of the composites was also improved.

Composite Resins↗
PubMed1993

Radiopacity of 12 visible-light-cured dental composite resins.

The radiopacity of 12 VL-cured composite resins was determined with reference to an aluminum step-wedge. Two anterior composites were radiolucent while two anterior and one anterior/posterior composites exhibited the radiopacity equal to, or slightly greater than, that of human enamel. Three posterior and one inlay composites possessed the radiopacity equivalent to, or in tiny excess of, that of human enamel. Three posterior composites had the radiopacity, fairly exceeding that of human enamel. Chemical analyses of the filler particles were carried out with SEM/EDX. It became evident that radiopaque fillers contained at least one radiopaque oxide component such as BaO, ZrO2 and Yb2O3 with varying concentrations. In general, the radiopacity of the composite resin was linearly proportional to the amount of the radiopaque oxide in the filler. It was suggested that ZrO2 was radiopacifier equivalent to, or even stronger than, BaO.

Composite Resins↗
PubMed1993

Dental high-speed cutting of four cast alloys.

The purpose of this study was to evaluate dental high-speed cutting behaviour of four cast alloys, namely Ag-Pd-Cu-Au alloy, Ag-Zn-In-Sn alloy, Ni-Cr alloy and Ti. Weight-load cutting tests were conducted on four cast alloys, using two rotary cutting instruments, namely a diamond point and a carbide bur, both driven by an air-turbine handpiece. While the constant transverse load of 80 g was applied on the workpiece for 5s, the handpiece speed was measured during cutting as well as the volume of workpiece removal which took place. The cutting tests were repeated 10 times. We found that the cutting volumes of soft Ag-Pd-Cu-Au alloy and Ag-Zn-In-Sn alloy were considerably larger than those of hard Ni-Cr alloy and Ti. It was also clarified that the cutting effectiveness of the carbide bur was generally superior to that of the diamond point. With continuing use, however, the cutting capability of the carbide bur tended to decline while that of the diamond point remained quasi-constant.

Dental Alloys↗
PubMed1993

Treatment of hepatocellular carcinoma by chemoembolization: evaluation with 3DFT MR imaging.

OBJECTIVE: We evaluated the usefulness of an MR imaging technique that used dynamic three-dimensional Fourier transformation (3DFT) fast imaging with steady-state precession (FISP) with gadopentetate dimeglumine for detecting viable regions of hepatocellular carcinoma following transcatheter arterial chemoembolization with iodized oil (Lipiodol). Images obtained with the 3DFT FISP technique were directly correlated with hepatectomy specimens. SUBJECTS AND METHODS: Dynamic 3DFT FISP MR imaging was performed after transcatheter arterial chemoembolization and before partial hepatectomy in 10 patients with 10 tumors of hepatocellular carcinoma. Imaging parameters were 20/8/30 degrees (TR/TE/flip angle) with a slab thickness of 21-75 mm and seven or 15 partitions. 3DFT FISP images were obtained at the slice level where a tumor had been detected on T1- and/or T2-weighted spin-echo MR images before, just after (early phase), and 1 and 2 min after (late phase) IV administration of gadopentetate dimeglumine (0.1 mmol/kg). We directly compared the dynamic MR images of the 10 patients with the gross and microscopic findings. RESULTS: On early-phase images, tumors of hepatocellular carcinoma showed no enhancement in three patients and partial intense enhancement in seven. Viable regions of the tumor showed intense enhancement relative to the surrounding liver parenchyma in the early phase, whereas necrotic regions showed no enhancement in either the early or the late phase. Both viable and necrotic regions had lower signal intensities than did the surrounding liver parenchyma in the late phase. By using dynamic 3DFT MR imaging, we were able to accurately assess the effect of transcatheter arterial chemoembolization with iodized oil in nine of the 10 patients. However, in one patient in whom microscopically viable cells were seen in the capsule of the carcinoma, viable regions could not be detected with our technique. CONCLUSION: Dynamic 3DFT MR imaging was useful in differentiating viable regions of hepatocellular carcinoma from necrotic regions following transcatheter arterial chemoembolization with iodized oil.

Aged↗
PubMed1993

Hardness and fracture toughness of commercial core composite resins.

One important mechanical property of core composite resins is fracture toughness, KIC, which expresses serviceability in the oral cavity, such as the resistance to marginal fracture. KIC values of eight commercial core composite resins were examined by the single-edge notched-beam (S.E.N.B.) method. Two composites containing about 80 wt% Si3N4 fillers exhibited both the highest KIC value of around 2.0 MN.m-3/2 and the highest hardness value. The other six composites containing 66 to 86 wt% SiO2-based fillers had KIC values of around 1.2 to 2.0 MN.m-3/2, and there was a tendency toward higher KIC values as hardness increased. It was speculated that the clinical acceptability of core composite resins could be broadened, if dental clinicians selected composites with higher KIC values.

Composite Resins↗
PubMed1993

[Case of diffuse esophageal spasm treated by long myotomy].

Diffuse esophageal spasm is a rare condition, which has generally been treated conservatively in Japan. A case of this disorder treated successfully by long myotomy is reported with a knowledge of prolonged pressure monitoring of the esophagus. A 56-year-old woman was admitted to our hospital with dysphagia. Barium swallow and esophagoscopy showed contraction of the esophagus, and manometry showed normal peristalsis, so the diagnosis of achalasia was ruled out. Prolonged pressure monitoring of the esophagus showed spastic contractions with the pressure over 130 mmHg that continued for 25 sec during meals, which led us to the diagnosis of diffuse esophageal spasm. Extramucosal long myotomy of the esophagus and a modified Belsey Mark IV operation were performed. The postoperative course was satisfactory and esophageal functional tests showed no spasms. The patient regained weight without dysphagia.

Esophageal Spasm, Diffuse↗
PubMed1993

Angiomyolipoma of the liver. Ultrasound, CT, MR imaging and angiography.

Angiomyolipoma, a rare benign liver tumor, was observed in a 50-year-old woman examined with US, CT, MR imaging and angiography. Dynamic studies using CT and MR imaging were valuable in differentiating the disease from hepatocellular carcinoma with fat deposits.

Angiography, Digital Subtraction↗
PubMed1993

Response to transcatheter oily chemoembolization in hepatocellular carcinoma 3 cm or less: a study in 50 patients who underwent surgery.

The response of 50 patients who underwent hepatectomy for hepatocellular carcinoma measuring 3 cm or less (at the time of surgery) to transcatheter oily chemoembolization was evaluated. The response was assessed in 5 categories, A: complete necrosis (100%), B: necrosis of at least 95%, C: at least 80%, but less than 95%, D: at least 50% but less than 80%, and E: less than 50% of the tumor cells. Response A was observed in 19 patients (38%), B in 7 (14%), C in 9 (18%), D in 7 (14%), and E in 8 (16%). These results were classified with respect to the histological degree of tumor differentiation, the WHO histological classification, the microscopic patterns of tumor growth, and macroscopic classification. The response was evaluated in relation to the histological grade of tumor differentiation and the WHO histological classification in all categories of response except response A, and there was no significant difference between the categories. The response was obviously better with the expansive type than with the replacing type. Single nodular type lesions were more responsive than the single nodular type lesions with extranodular growth and the contiguous multinodular type. Pretreatment estimation of the microscopic patterns of tumor growth and macroscopic classification appears to be valuable in predicting prognosis.

Adult↗