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Biomedical subjects

S Takehana

Publications and source records attributed to S Takehana.

At least 37 records · Page 2Linked to original sources
PubMed1989

[Strengthening for dental porcelain surface].

UNLABELLED: Although the metal crown is aesthetically improved when porcelain is fused to it, a large number of different factors often cause the porcelain to break. Here we report a method to prevent this from happening. As a hardening treatment for the porcelain surface, the Na-ions in the porcelain, which have a short radius, were replaced by K-ions having a long radius to strength the surface against compressive forces. RESULTS: 1. The bending test showed that the strength of the porcelain had increased from 20 to 38%. 2. The hardness test indicated that the strength had increased from 23 to 24%. 3. The breaking test showed that although the strength of the porcelain had not increased to any great extent, the strength of the veneer shell had increase by more than 30%. 4. The EPMA measurement showed that ion replacement had penetrated to as much as 50 to 80 microns. 5. Clinical tests indicate that even after 19 months, the surface of the porcelain remains the same and that the condition is quite stable.

Dental Porcelain↗
PubMed1989

[Dimensional change and deformation on stone dies for full cast crowns. Differences according to impression methods using vinyl silicone impression materials].

In order to reconfirm the efficiency of an individual tooth tray, an apparatus and method were developed for measuring dimensional changes and observing over all deformation on a stone die for a full cast crown. The stone dies, which were made by combination impression methods I, II and double impression (individual tooth tray use) with vinyl silicone impression materials, were measured and compared. The results were as follows: 1. It made no difference what kind of vinyl silicone impression materials were used. 2. As to the dimensional changes: for combination impression method I, irregular results were found for the stone dies with the differences between +1 standard deviation (SD) and -1 SD being large. The variations of the other two methods were quite small, indicating that the stone dies were made accurately. 3. Observing to magnified images with the naked eye, there were no clear differences between the three methods on the marginal parts, but at the top corners of the stone dies there were good results with the double impression method. 4. It was possible to grasp easily the general aspect of dimensional changes in the stone dies using this newly developed measuring method.

Calcium Sulfate↗
PubMed1989

Correlation between the degree of deformation of the stone die and the amount of the master die undercut. Part 1. Single tooth die.

In order to investigate the deformation the stone die depending on the amount of undercut, 5 kinds of undercut master dies were used to take impressions using 3 kinds of impression materials (addition type silicone rubber, polysulfide rubber, alginate). The stone dies were measured for dimensional changes in shape as projected to a two-dimensional plane by means of a newly devised apparatus. The results showed that deformation of the stone dies increased, in general, in proportion to the amount of undercut of the master die. The stone dies obtained from addition type silicone rubber impression material tend to be less deformed. In the case of the polysulfide rubber impression, the deformation was very small in stone dies in the case of non-undercut master dies, but it was very large in the case of undercut master dies. The alginate impression materials gave results with wider variations.

Alginates↗
PubMed1987

A clinicopathological study of ameloblastomas.

72 cases of ameloblastoma were obtained from the files of the Department of Pathology, School of Dentistry, Aichi-Gakuin University for the years January 1970 through December 1983. The cases were analyzed with respect to sex, age, duration, site histopathology, and treatment. Of 72 patients, 63 had no previous therapy, while 9 received their initial treatment elsewhere. There were 38 males and 34 females, a ratio of 1.2: 1. At the time of diagnosis, the ages of all patients ranged from 11 to 71 years, with an average of 36.6 years. About 65% of patients were in the 2nd, 3rd, and 4th decades of life. The duration of symptoms varied from 2 days to 5 years, with an average of 12.6 months. 69 cases occurred in the mandible, with the molar-ramus region being the most frequent site of involvement. Only 3 were found in the maxilla. The left side of the mandible was affected 1.6 times more frequently than the right. Histopathologically, 44 cases were of the plexiform type, 15 the follicular, 10 the acanthomatous, and 2 the basal cell type. Only 1 case was of the granular cell type. Most of the findings in the present study agreed with previous available data from the literature on ameloblastomas.

Adolescent↗
PubMed1985

Papillary cystadenoma.

A rare case of a papillary cystadenoma, mucous-cell type, in the lower lip of a 73-year-old male is presented. The tumor consisted of many small cysts with multiple papillary projections into their cystic spaces. The projections and cyst walls were lined with pseudostratified mucous-cell epithelium. Clinically and histologically, the present papillary cystadenoma was considered as a true tumor originated from the ducts of minor salivary glands. There exists only one case report of a papillary cystadenoma with adequate description and photomicrographs in the Japanese dental literature.

Aged↗