For the study of phylogenesis of the human teeth, the morphological study on the teeth of the primates is extremely important. From this aspect the author has investigated the morphology of permanent both maxillary and mandibular teeth of the Japanese monkeys, which belong to the catarrhini macaque, believed to be closest to the man, and anthropoid apes, and the author has obtained the following results : 1. The lingual cingulum of maxillary incisor and mandibular canine was comparatively well developed, but the development of the cingulum in other anterior teeth region was scarcely observed. 2. In the buccal surface of both maxillary and mandibular premolars, the cingulum was observed to be developing comparatively well. 3. Whereas the general rule of the premolars was 2 cusps, developmental degree of the metaconid was apparently inferior to that of the protoconid of the mandibular first premolar. Also it was noticed that in the mandibular second premolar the development of metaconid was exceedingly well, and the differentiation tendency of the entoconid or the hypoconid was observed to develop 3 or 4 cusps. 4. The development of the cingulum of the molar was not so remarkable, but it was noticed that the molars of the distal side, the second and third molars, showed better development than the first molar. 5. In the occlusal surface pattern of the maxillary molars, the paracone was contiguous to the hypocone. And the maxillary molars built bilophodonty, which was connected by transverse ridge ranging both buccal and lingual cusp on each mesial and distal side. This was different from the man or anthropoid apes where the metacone is contiguous to the protocone by the oblique ridge. 6. In the survey of the Carabelli's cusp, the median lingual accessory groove cusp and the distal accessory cusp as the supernumerary tubercle appearing in the crown on the maxillary molars, it was observed that they appear mainly in the third molar and that the mesial marginal tubercle was seen mainly in the first molar. 7. The mandibular first molar had 4 cusps in all cases and every mandibular third molar had 5 cusps, while the mandibular second molar was mostly of 4 cusps with exceptional 5 cusps. 8. The occlusal surface pattern of the mandibular molars showed the same bilophodonty as the maxillary molars, different from the Dryopithecus pattern, the basic type of the man and anthoropoid apes. 9. In the survey of the 6th cusp, 7th cusp and protoconid as the supernumerary tubercle appearing in the crown of the mandibular molars, they were not seen in the first molar but many were found in the third molar. 10. The measurement of tooth crown showed greater size in the male than in the female, and such a sexual difference was most peculiar in the canines. 11. In the molars the mesiodistal diameter was greater than the buccolingual diameter. This difference was more obvious in the mandibular molars. 12. Comparing the mesial and distal side on buccolingual diameter of the molar, it was observed the former is larger than the latter in all cases, and that the diameter is reduced toward the distal region from the mesial region in each molar.

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A thorough knowledge of the morphological characteristics and the sizes of the human natural teeth will be of an important reference in prosthetic restoration of the teeth. If dental crown surface area can be accurately determined, the knowledge, together with that of the dental root surface area, will be of value in ascertaining masticatory requirement. Measuring the dental crown surface, however, is difficult because the forms of the dental crowns are irregular and uneven. The author, therefore, examined a silver-plating measurring method for irregular shaped test pieces. A preliminary experiment was conducted with 60 regular-shaped measurable test pieces comprising 6 varieties each of two types and modifications were made on the method. A total of 140 extracted natural teeth, 14 pieces each from each position, were measured by the modified method. The results obtained were as follows : 1. Duplicates of the test pieces to be measured were mode with epoxy resin and non-electro and electoro plating were done on the surface. The surface areas (A) was obtained by applying to the formula A≒K/w・r, the value ascertained of plating weight (K), plating thickness (w), and specific gravity of plating (r). 2. The surface areas of the duplicate test pieces were measured by the modified plating method and the measurements were compared with the theoretical values calculated mathematically in advance. An average error of 0.6% was obtained as a result. 3. The crown surface areas were : of the upper jaw, central incisor : 242.3mm^2, lateral incisor : 195.8mm^2, canine : 229.0mm^2, first premolar : 226.6mm^2, second premolar : 203.0mm^2, first molar : 344.1mm^2, and second molar : 312.4mm^2. Of the lower jaw, central incisor : 146.0mm^2, lateral incisor : 155.0mm^2, canine : 187.9mm^2, first premolar : 190.0mm^2, second premolar : 184.3mm^2, first molar : 351.3mm^2, and second molar : 314.4mm^2. 4. The ranks of sizes in descending order were : of the upper jaw, first molar, second molar, central incisor, canine, first premolar, second premolar, and lateral incisor. Of the lower jaw, first molar, second molar, first premolar, canine, second premolar, lateral incisor, and central incisor. 5. The first and second molars of the lower jaw showed greater values than the corresponding teeth of the upper jaw. For the other positions, those of the upper jaw showed greater values.

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[in Japanese]

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1) Progress of deciduous caries incidence and appearance and fluctuation of streptococcal organisms in dental plaque in 29 infant subjects aged 13 to 17 months after birth were examined 3 times at every 6 months intervals. 2) It was confirmed that most frequent organisms to be found there proved Str. mutans, Str. sanguis and other unidentified organisms, of which Str. mutans showed an increasing rate of growth with progressive months after birth. 3) The subjects were divided into caries active group showing caries incidence during the experimental period and caries free group showing no caries incidence. The former group was characterized by higher rate of detection of Str. mutans in plaque already at the start of experiment which increased with progressive months. This suggested that Str. mutans among other species of Streptococci would have closest association with the incidence of deciduous tooth caries. 4) When time at which caries lesion started in the deciduous teeth and time at which Str. mutans first appeared were studied, it was revealed that Str. mutans made its first appearance 6 to 12 months prior to the onset of caries lesion. However, it should be noted that among the subjects who showed Str. mutans in plaque, those who suffered dental caries amounted to 81% and the rest remained healthy of tooth in spite of the presence of this organism in plaque. 5) Mode of sugar intake by snack eating habit was studied by asking questions with the subjects, and acid resistance of tooth was examined by estimating the amount of phosphate dissolved with use of agar plate method. 6) Appearance and fluctuation of Str. mutans in plaque, mode of sugar intake and amount of phosphate dissolved, these 3 sets of data were respectively combined with the mutans score, sugar score and phosphate score to serve for obtaining knowledge about she interrelation with caries incidence. 7) Each score for the above 3 factors did not necessarily show the parallel relation with development of caries lesion. However, combined data of above 3 factors showed the distinct difference lying between the caries active group and caries free group of subjects. 8) If one is allowed to forecast the caries incidence to occur 6 to 12 months later only by the knowledge about Str. mutans, the chances are approximately 80% at the most, but if the data for sugar intake and acid resistance of tooth were given additionally, probability of his forecast would be increased to about 90%. 9) A positive correlation was shown to exist between the acid production potential of plaque and colonization of Str. mutans accompanying the dental caries incidence.

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In the course of some forty years since the adaptation of acrylic resin by liquid-powder polymerization in making dentures, modifications and improvements have been made in its properties and polymerization techniques. Although heat curing type resin with plaster cores is in main use currently, the use of pour type resin and self curing type resin in also on the increase clinically. Many reports have been made to date on the studies of these resins, but the matter that which polymerization technique may be the most clinically favorable still remains unsettled. In the present paper, therefore, an investigation was made of the effect on the resin test plates of the difference in the kinds of resin, cores, polymerization techniques. For the study, two types of experimental metal models of upper denture and resin test plates of heat curing type resin, pour type resin, and self curing type resin were prepared. The results obtained were as follows : 1. Measurement of thermal conduction of plaster, silicone and agar, used for cores, revealed that plaster showed the best conduction, under given conditions, then agar and silicone followed in order. 2. In dimensional accuracy and adaptability, self curing type resin was superior to heat curing type resin in both plaster core method and silicone core method. 3. As the core materials, silicone core method has less inner stress because of its smooth surface. On the other hand, this method was slightly inferior to plaster core method in dimensional accuracy and adaptability. 4. Heating factor during polymerization affected the dimensional accuracy and adaptability of the polymerized resin test plates. 5. Higher temperature for water-bath for submersion of the test plates after polymerization released inner stress sooner and at a high rate in time. 6. In the form of the resin test plates, shallow palate type showed less deformation rate and less degree of change with time.

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Zinc and copper levels in rabbit bearing VX_2 carcinoma were determined with the flameless atomic absorption spectrophotometer. The levels in plasma, tumor, femur muscle surrounding tumor, non-planted femur muscle, liver, spleen and pancreas were surveyed on the third day after implantation and every week for six weeks. These data rearranged into five groups (stage 0-IV) along with the growth of tumor. The plasma zinc decreased in stage II and III but the copper increased. Then the Cu/Zn ratio was high level as in malignant tumor patients. The zinc levels in tumor in stage II, III and IV were higher than those in stage 0. The zinc in the surrounding muscle of the VX_2 carcinoma decreased in stage I and III. Its levels in stage II and III were lower than those of the control opposite muscle. The zinc concentration in tumor could be accumulated via surrounding muscle because of its level in the other side was almost the same. The zinc and copper in liver increased in stage II, III and IV and the Cu/Zn ratio decreased. The levels in pancreas showed no changes between the control and the tumor groups, but the Cu/Zn ratio in stage II and III were significantly higher than those in the stage 0. The neoplastic liver and pancreas are antagonized under the biochemical changing from the point of Cu/Zn ratio. These results described above justly offer further investigations for clinical surveys in neoplastic disease.

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Compared with resin base dentures, metal base dentures have many advantages but also have disadvantages of difficulty in adjusting and also in rebasing after insertion. Elimination of such shortcomings will make the metal base dentures quite ideal, particularly for the maxilla. For the present study, dynamic impressions of resin base dentures conventionally completed were taken, the functional forms of basal seat area were recorded, and the working casts were made. Then, metal base dentures were made based on the working casts. The results were as follows : 1. The use of dynamic impression made it possible to duplicate the functional form of basal seat area on the metal base. 2. Because the deformation produced in curing process of resin preparations and by release of the inner stress did not affect the basal seat area of the denture, better fitting dentures could be made. 3. Lining the joint between the artificial teeth and the metal base with heat shock resin minimized deformation during curing. Consequently, good fitting at insertion was obtained and little adjustment was required. Prognosis at the present time, three years after insertion, is also good.

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Radiographic examination is one of the important clinical examinations in dentistry. Recently a great many radiographic examinations are used in the special field of dentistry. The purpose of this study was to analyze the 97, 654 radiographs (38, 414 patients) taken at the Kyushu Dental College Hospital from 1970 to 1975. The results obtained are as follows : 1. The number of annual radiographs taken increased with the increase in outpatients and the number of radiographs per patient. The number of the orthopantomographs taken is increasing yearly. 2. The number of the periapical dental radiographs decreased temporarily in 1971 but increased steadily later. This fact means that the orthopantomography is not a radiographic technique which replaces the periapical dental radiography in the radio graphic examination of the dento-maxillary region. 3. The periapical dental radiography and the orthopantomography serve different purpose for radiographic examination. The periapical dental radiography should be used for qualitative diagnosis and the orthopantomography for quantitative diagnosis.

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Orthopantomography is recently used not only in dentistry but also in otorhinolaryngology. The orthopantomograph, which is manufactured by the Siemens Corporation, has two different mechanical systems ; N projection and S projection. N projection means a normal projection which is used as a routine technique, and S projection means a special projection which is used for examination of the maxillary sinus or the temporomandibular joint. The purpose of this study is to compare the S projection with the N projection regarding the roentgen anatomy of the maxillary sinus. The results obtained are as follows : 1. The roentgen anatomy of the maxillary sinus is different in N projection and S projection ; the anterior wall and the posterior wall are superimposed upon the medial wall in the N projection, but in the S projection only the anterior wall is superimposed upon the medial wall. 2. In the N projection, the inferior nasal concha and the zygomatic bone are superimposed upon the maxillary sinus but are hardly superimposed in the S projection. 3. The S projection is a better technique than the N projection for the roentgenological examination of the maxillary sinus.

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