For the purpose of improving the strength of dental porcelain, investigations were made on its mechanical properties, especially bending strength and thermal expansion rates by the use of a chemical strengthening method, resulting in the following conclusions:

1) Relation between treatment temperature and bending strength: The bending strength reached the mechanical properties, especially bending strength and thermal expansion rates by the use of a chemical strengthening method, resulting in the following conclusions:

temperature surpassed 550℃.

2) Experiment of the treatment time with KNO₃ molten salt at 500℃ resulted in that increasing the treatment time the stronger the bending strength, that the strength became maximum by 5 hours’ treatment, and that the maximum strength was more than twice that of untreated porcelain.

3) From the relation between treatment temperature and thermal expansion rate, the higher treatment temperature induceed the higher thermal expansion rate. The maximum rate was obtained at 550℃. If treatment temperature surpassed 600℃, thermal expansion rate showed decrease.

4) With regard to the relation between treatment time and thermal expansion rate, the expansion rate iscreased in proportion to the increase in the length of treatment until it reached the maximum aftter treatment for 5 hours’. The thermal expansion rate showed only a small increase even by 7.5 hours’ treatment.

An extracellular deoxyribonuclease separated from Streptococcus sanguis I destroyed the thymus DNA and then produced mono-, di-, tri-, tetra- and other oligonucleotides.

These oligonucleotides were determined by the combination of Sephadex G-25 gelfiltration and DEAE-Sephacel ion exchange chromatography in the presence of 7M urea.

The results were summarized as follows:

Only thymus DNA was hydrolyzed by the DNase and its molecular weight decreased to 2.2 x 10⁵daltons on 0.8% agarose gel electrophoresis. However, the DNase showed no enzymatic activity for λ phage DNA, fd phage DNA, thermally denatured thymus DNA or themally denatured thymus λDNA.

It suggests that the DNase has high specific activity for native thymus DNA.

The ultrastructural and immunohistochemical studies were made on the labial salivary glands in patients with Sjögren’s syndrome, and peculiar histopathologic findings were reported, As the results of present investigation a hypothesis is put forward that the epithelial cells of the intercalated ducts represent the target cells for the infiltrating lymphoid cells. The hyaline-like substance in and around altered ducts and epimyoeplthelial islands may contain antigen-antibody complex in part.

This study examined whether the intensity of haloperidol-induced catalepsy in ddY strain mice was modified by repeated administration of haloperidol (HP), using different doses and different intervals. HP was dissolved at the concentration of 1mg/ml of 0.1M tartaric acid and further diluted with a saline solution to administer the volume of 0.1ml per 10g mouse. HP at 0.075, 0.3, 0.6, 1.2, and 4. 8mg/kg were orally administered at three different intervals: daily (successive administration), every 2 and 4 days (intermittent administration), for 21 days. The intensity of catalepsy, namely the duration of time that the mice remain immobile on a horizontal bar, was measured 3 hours after the administration of HP. In repeated administration of HP at 0.075 and 0.3mg/kg no modification was observed for any of the administration intervals. In the case of HP at 1.2 and 4.8 mg/kg, the intensity of catalepsy decreased with the successive administration, on the contrary, it increased in response to the number of administrations with the intermittent administration. The mode of the modification to HP catalepsy varied with the administration intervals, that is, a tolerance developed with the successive administration, whereas a reverse tolerance developed with the intermittent administration.

Diazepam was given intravenously for the purpose of treatement of anxiety occuring during dental treatment to the four heart disease patients. All patients were old age. The results were summerized as follows.

1), No significant change was obserbed in respiratory and circulatory function during sedation and operation. But one patient was found a little decrease in respiration.

2), E.C.G. monitor and it’s record was employed continually during sedation and operation. One patient fell temporarily into ventricular arrythmia during sedation. But the other patients did not fell into arrythmia during sedation and operation.

For radiation dose reduction of patients in dentistry, it is a significant method to use new high-speed dental X-ray film, EKTASPEED.

The purpose of the present study is to compare the characteristic curves by EKTASPEED and ULTRASPEED used to this time and to compare diagnostic performances were examined on image quality and granulation of these radiographs created on molar portion in mandibular bone with bone phantom.

The characteristic curve of EKTASPEED was approximately parallel to that of ULTRASPEED and gamma was nearly equal each other.

The speed of EKTASPEED was twice as fast as of ULTRASPEED. Radiographs by EKTASPEED were somewhat rough in granulation, whereas there were no significant differences between EKTASPEED and ULTRASPEED on image quality.

Diagnostic performances of EKTASPEED were almost same as those of ULTRASPEED.

The results suggest that the choice of new high-speed dental X-ray film, EKTASPEED, is useful for radiation dose reduction of patients.

For ten years clinical and radiographic obsavations of a tooth with horizontal mid-root fracture were continued. In this case, the antibiotics was administered immediately after traumatic injury. At one week after injury, the tooth was repositiond and fixed with adhesive composite resin.

At three weeks after injury, the tooth became sensitive to the chilled water, and then the pulp was extirpated. At the next appointment, root canal was filled with guttapercha points and root canal sealer. At ten years after injury, there is no radiographic chenge of supporting structures except for the exisstance of broad separation between two fragments. Moreover, no clinical change is observed and the tooth functions well.

It seems that the traumatized teeth which have a root fracture of middle third need necessarily to be extracted, even if pulp necrosis occurs.

Recent clinical reports have described the use of endosteal blade implants as abutment teeth for the fixed partial dentures and is foundamentally acceptable in practice. There has been, however, scant information regarding the healing process around the neck of implant where contact with soft tissue.

We have experienced a patient who had pain and disorder after worn the implant denture which was fixed partial denture constructed by a blade vent implant imbeded at the site of right canine as a abutment tooth.

Examination was revealed and determined the prognosis of implant denture was poor. Radiographically, resorption of alveolar bone was also noted at the under surface of the implant denture. After removal the implant with surrounding tissues, histopathological examination was made to determine the affect of the tissues under the implant denture.

The observation indicated that the implant was not passively accepted by tissues and these areas tissue did appear to show progressive changes with inflammatory reaction.

There must be some doubts as to whether dental implant may be carried out with better results rather than properly designed removable partial denture.