40 strains of Neisseria isolated from the oral cavity were investigated bacteriologically and immunologically. 14 strains were identified as Neisseria sicca, 4 strains as Neisseria catarrhalis and only 1 strain was Neisseria crassus. The remainder were intermediate in many respects.
In order to know how to master the dental laboratory techinique (D.L.T.) and how to teach it, experimental study was undertaken taking 743 dental students and 254 students of dental technician school on trial. Results obtained as follows : I On the D.L.T. 1. D.L.T. is influenced by one's own disposition. Therefore, the abtitude tests must be given for the dental applicants. Penmanship with Japanese brash and drawing pictures are recommended as the best method of abtitude tests, because they have an intimate connection with D.L.T. 2. In the training courses of D.L.T., it is necessary to intend to gain good quality of the workmanship than to complete it rapidly. 3. It must not be competed with another in finishing time. 4. 3-3.5 hour's laboratory work is the most effective. If continue moreover, workmanship of excellent quality will not be expected. 5. Even if we give enough time to the students, advanced quality of the workmanship can not keep up, unless they have not any interest and volition on it. 6. Physical fatique have little influence upon the quality of the workmanship. 7. When we continue to make a certain workmanship for a long time, declining quality appears earlier than losing speed. 8. Training effect of the same kind of workmanship appears after making 3 or 4 pieces. 9. When a student who got tired on his laboratory work is forced to continue, the result appears in declining quality. 10. If the works are simple or experienced one, shortening of finishing time appears, earlier than deterioration in continuous work in which same workmanships are made over again. 11. There is no difference between continuous training and intermittent training. 12. Efficiency of the work is rather superior in the afternoon to in the morning. 13. The more splendid in school records are, the more splendid in dental techinique are and vice versa. 14. D.L.T. has strikingly intimate relation with natural scientific subjects. 15. D.L.T. has no relation with physical rocords. 16. D.L.T. has not direct relation with the sense of sight. 17. Dividing the students into two groups, for instance one is skillfeel and another is unskillful in D.L.T., each group has common characteristics 18. The students skillful in D.L.T. is careful in everything and keep their sorroundings in good conditions (cleaning of the laboratory room and desk, full-equipped mashines, a.s.o) . II On the teaching method of D.L.T. 1. How to instructe the student who is poor in quality for D.L.T.- a) Such a student should be placed in a left or right side or at the front of the student having good quality. b) The effect of such treatment depends upon the period of time and the distance between them. c) But, it their making speed difference remarkably or they are making different workmanehip, we can not expect the effect of such treatment. d) we had better give him self-confidence than point out his, disadvantages. At least we must not refer to his advantages positively. 2. The workmanship of the students is influenced by their life enviroment, especially economical instability. 3. Change of general feeling and physical fatigue exerts sometimes good and some-times bad effect upon one's workmanship. 4. To praise is a good stimulation for making excellent workmanship. 5. All the students are very sensitive to the feeling and behaviour of the instructors.
According to the recent conception of the vital reactions which occur in injured or inflamed pulp tissue, it is known that the pulp tissue is endowed the power, enough to protect and recover it'sself from injury or inflammation. But the conservative treatment of pulpitis is so difficult that the pulpectomy or pulpotomy prevails generally as therapeutic methode in daily practice. The difficulty of the treatment of pulpitis lies in that the inflammation is apt to get worse rapidly and the treatment is not carried out without irritating the pulp seriously, for it is surrounded by the hard tissue. In such cases, it seems that the treatment of pulpitis is possible to perform without giving any irritation to the pulp, if the causes or complications of inflammation such as, bacteria, toxin and the high inner pressure of the pulp chamber are able to be subsided by means of application of the direct current. Therefore, author observed how the electroosmosis in wide sence, is conducted inn both extracted human teeth and dog's teeth in situ. And the result were as follows. 1) The healthy dentin (ςD), coloured hard carious dentin (ςK), combined material of den-tin and cement (acquired at the wall of the root canal) or cement only (ςz) and pulp tissue (ςp) etc. are electrically charged negative in the solvent at about pH 7.0 and. the comparison of each zeta-potential is ranged as shown|ςD|>|ςz|≅|ςK|>>|ςp|. 2) The zeta-potentials of the dental hard and soft tissues show no considerable difference between human and dog. 3) The more the pH inclines to a!kalic in the solution between a range of pH 4.3 to 11.2, , the higher towards negative the zeta-potentials become. 4) Cation (Ni++) is most quickly transported in human dentin and follow anion (Cl-) and neutral substance (HCHO) by either cataphoresis or electroosmosis. 5) Anion is so quickly transported in dentin by direct current as to pH inclines to acidic and cation or neutral substance is transported so quickly as to pH inclines to alkalic. 6) It is observed in the extracted human teeth that the anodal application of direct current to the occlusal cavity, filled with physiological saline solution raises the inner pressure of the pulp chamber and the cathodal application on the contrary, decreases. the inner pressure of the pulp chamber. 7) And also observed in dog's teeth in situ, that the anodal application of direct current to the cavity decreases the inner pressure of the pulp chamber and the cathodal application on the contrary, raises the inner pressure of the pulp chamber. 8) To treat pulpitis, the anodal application of the direct current is considered to be favourable.
This report describes and evaluates some of the recent improvements and developments in dental handpieces in Japan which make them suitable for increased speeds of rotation. Vibration, temperature on sheath of handpieces have been studied, and special designed handpiece has been shown the good results for the test of vibration caused by increased speeds of rotation, temperature on sheath rising by friction.
W. H. G. Logan (1921) and other investigators have examined the edentulous ridge roentgenographically and found various kinds of remnants in the ridge, which has led them to assert the importance of taking roentgenogram of the whole parts of upper and lower jaws before impression. This made us examine the roentgenogram of whole jaw of complete denture wearers and compare the results obtaind to those being reported by the previous investigators. Materials studied in this report are the roentgenograms of edentulous ridge having taken during 14 months from July 1952 to September 1953 at the Department of Prosthetic Dentistry, Tokyo Medical and Dental University and at Dr. Ogata's Dental Clinic. In 179 cases (103 patient) studied, the patients age ranged from 41 to 80 years old (average 56 years old) and their denture wearing period was ranged from one month to 26 years (average 7 years) . The results obtained were as follows : 1) 55 cases (30.7%) out 179 edentulous cases had some remnants in the ridge. 2) In only 3.3% of cases with remnants in the ridge the patient had awared to the existence of some abnomalities in the ridge, while the other had no subjective symptom with no clinical symptom. 3) The results obtained by this study led us to the conclusion of that it is necessary to take roentgenogram of edentulous ridge before impression in daily clinical work in order to secure the successful complete denture, and that the simultaneous use of both the ordinal size of dental film and the occlusal size of film were as well recommandable for this purpose.
The patient, 26 year old farmer, had pressure feeling at the distal region of the upper and lower second molar about two years ago. X-ray examination found the 6 super-numerary molars embedded in the distal portion of the upper and lower second molars on the both side. These supernumerary molars were operatively removed except the left maxillary distal one because of difficulties of extraction. According to the macroscopic examination, these supernumerary teeth were identified as 4 th or 5 th molar. These teeth had relatively well developed crown, while their roots were short, round and blunted.