It is well recognized in the orthodontic practice that the ratio of the magnitude of the jaw bones relative to the full arrangement of permanent dentition should be within the range of 1.1 to 1.20. When the ration in a patient fell below this figure, there usually occur more or less an imbalance or so-called disharmony of magnitude between his jaw bones and his permanent dentition. In the clinic of orthodontic practice where patients with deciduous dentition are most frequeutly to be treated, it is desirable for the operator to have some criteria with which he could predict an exact magnitude which the permanent dentition and the jaws would respectively attain at definite future age of an patient. The future magnitude of one's permanent dentition may be predicted with reasonable accuracy by means of roentgenography of the teeth and other methods of measurement. Such prediction, however, is difficult with the future magnitude of the jaws because there is no available information as to the growth rate of jaws to be seen at these age stages of the patient. The present author undertook to study the growth rate of jaws on a total of 33 subjects consisting of 16 males and 17 females ranging in age from 6 to 15 by taking serial gnathostatic models from each subject for masurement. The data obtained showed that the mean increment in the magnitude of jaws of male subbjects amounted to 22±5mm and that of female subjects 21±5mm during the period of 9 years. This means that these subjects had a mean annual increment of 2.4mm of jaws through the 9-year period. The maximum and minimum values of the increment were shown to amount to 33 mm and 15 mm respectively during the same period. The study suggested that these figures would be of some help for the operator in predicting an approximate magnitude of jaws of a patient at his 15 years of age and thus would serve as criterion for tooth extraction in correcting the case of disrepancy.

抄録全体を表示

A cross section survey for the year 1968 was conducted on the possible correlation existing between the physique and the permanent tooth erupution in younger generations, using a total of 5, 508 subjects of both sexes consisting of those regional groups who resided respectively in Yawata of Kitakyushu metropolitan city, Nakatsu city and its suburban small industrial and farming communities. The permanent tooth eruption was studied with respect to relative speed at which individual teeth came into full eruption by calculation of correlation and regression coefficients and by analysis of covariances. Results obtained were as follows. 1. There was noticed some regional difference in the eruption time of the permanent dentition in that the eruption was earliest in Nakatsu group, followed by the rural community groups and Kitakyushu metropolitan group. 2. Study on the pattern of frequency distribution curve with regard to the number of erupted permanent teeth showed that L type was observed to occur in subjects 6 to 7 years of age and the normal type of curve occurred more or less in subjects 8 to 10 years of age, while J type was more frequently observed in older age groups toward 15 years of age. This change of patterns from L type to J type with advancing age was seen earlier in the female subject groups than in the opposite sex groups. 3. The relative speed with which individual teeth came into eruption was referred to as the eruption grade and studied comparatively among teeth. The time required for any tooth to reach its normal occluding position from their incipient stage of eruption was referred to as eruption time comprising 3 successive stages. The shortest eruption time required for incisors and first molars was from 5 to 7 years, and the time required for canines, first and second premolars and second molars was in the range from 7 to 9 years. 4. physique and Eruption of Permanent Teeth When correlation between the permanent teeth eruption and the physique of subjects of both sexes in every age stages from 6 to 15 years was studied, it was shown that the correlation coefficient with body weight ranged from -0.12 to 0.51 for the male sex, -0.21 to 0.54 for the female, and that with body length-0.09 to 0.50 for the male and -0.55 to 0.41 for the female. Although the correlation of the physique of subjects of both sexes with the number of permanent teeth eruption could be concluded to be highly significant in general, the values of coefficients obtained for each age stage differed considerably. Nevertheless, general trend showed that the correlation was strongest in youngest age groups and became gradually smaller from 6 years toward 15 years of age of subjects as shown in the regression line. 5. Covariance was calculated by analyzing the correlations of the permanent teeth eruption with each of age, body length and body weight of subjects. The results showed that the correlation between age was stronger than the ones between either body length or body weight. All these aspects of correlations between physique and permanent teeth eruption were studied perspectively by means of correlation coefficient and regression line as calculated for every age stages of subjects from 6 to 15 years of age. The results showed that the correlation coefficients for all class (age, body length and weight versus permanent tooth eruption) and for between class (age versus permanent tooth eruption) were far greater than those for within class (body length and weight versus permanent tooth eruption).

抄録全体を表示

Using a dental X-ray apparatus, an investigation was conducted to analyze a variety of factors that will influence the scattered X-rays from the exposed object and those distributed within the object. The factors involved included physico-chemical nature of object, thickness of object, the tube voltage and the field area of exposed X-rays. As preliminary experiments, water and wax phantoms were exposed with a dental X-ray apparatus and the primary and scattered X-rays distributing within each object were respectively measured. In the next step, the surface scatter doses of each object were measured and the relation between their distribution and the above factors which would influence upon them were studied. The scatter distribution doses were measured mainly by the X-ray film density method, and the quality of scattered X-rays was measured by the half value layer method with aluminium. The study showed that the maximum scatter distribution dose was found to lie around the depth of half value layer of the object radiated which gradually decreased past that point toware the transmission surface. The scattered X-rays generated in the object were dispersed in the whole body toward every directions, of which the back scatters were more abundant near the exposure surface and the front scatters more abundant elsewhere, but the latter decreased toward the transmission surface. When the soft matters such as human tissues were radiated, the less the X-ray absorption coefficient of the object, the more increased all surface scatter doses. The dispersion rate at the exposure surface and transmission surface increased gradually with the increase of any one of the factors such as thickness of the object, field area and tube voltage of the X-rays until it reached saturation. With increase of thickness, the back scatter doses radiated from the object increased gradually towrd saturation, while the transmission scatter doses decreased inversely when the thickness of the object surpassed its maximum transmission scatter value. Every surface scatter doses of the object increased with the increase of tube voltage or field area of X-rays. When it deals with hard matters which are difficult to transmit for dental X-rays, only very small amount of back scatter doses could be observed. The metalic plates such as Pb, Fe and Cu showed only less than 5% back scatter doses of that produced by water phantom. Correspondingly the back scatter doses from these hard objects were hardly affected by changes of thickness of the object and tube voltage apllied within the limit of dental X-ray. Tha quality of surface scatters differed with respective radiating direction from the obiect irradiated. The transmission scatters were essentially identical with the primary transmission X-rays in quality. The mean wave length of back scatters, however, became a little shorter with increasing of thickness of the object, but it never reached the mean wave length of the primary X-rays. Since the mean wave length of lateral scatters became shorter only by the photo-electric absorption effect of surrounding tissues outside of the exposure field, it was often found that the mean wave length of lateral scatters became shorter than the primary X-rays according to the nature and thickness of the surrounding tissues. In the actual case of intraoral roentogenography, the scatter doses measured on the cheak surface of patient were about 13% and the same measured within oral cavity were about 9% of the total surface X-ray doses, and about one third of the intraoral scatter doses was consisted of back scatter doses from the intraoral surrounding tissues. It was confirmed that 30 to 60% of the total film density of the intraoral roentgenogram was caused by intraoral scatters of which 30 to 50% was responsible to back scatters of intraoral surrounding tissues.

抄録全体を表示

The author experimented with the use of permanent teeth of dogs on purpose to retain a residual pulp in the more apical portion (Low Positional Pulpotomy) and in the more coronal portion of root pulp (High Positional Pulpotomy) with the use of medicament Calvital (a commercial form of calcium hydroxide) and the other six sorts of root canal filling medicament, a histopathological study to the healing process of residual pulp was made and summerized as follows ; 1. The case, which is the case of closing the wound surface of the pulp by the newly formed dental hard tissue, "so-called dentine barrier" was observed more in the group of High Positional Pulpotomy than in the group of Low Positional Pulpotomy. 2. Histologic structure of the dentine barrier was observed in various appearances from primary dentine to osteoid dentine, but the formation of these barrier was considerd as closely related not only to the function of pulp tissue, but also to the effects by the sort of medicaments used. 3. The formation of these barrier was observed most in cases of the used medicaments, Calvital and Calsan A and showed a tendency that the beginning of the formation was about 10 days postoperatively and the complete closure of the wound pulpal surface was about 20 days postoperatively. The structural condition and the thickness of the barrier were fairly better in case of the used medicament, Calvital. 4. When the High Positional Pulpotomy procedure was employed, each medicament made some differences to the reactive change in the pulp, but in relation to the successive change, some roughly regular changes were observed. When the Low Positional Pulpotomy procedure was employed, however, there were many cases which showed that a great deal of reactive change, caused by the instrumental effect due to the difficulties of the procedure, and there were a few cases which showed regular successive and histological changes to the medicaments used. 5. In case of Low Positional Pulpotomy employed, there were many cases, showed that the root canal were overfilled due to the difficulties of filling technic, moreover, induration or degeneration of the residual pulp tissue due to the instrumental oppression was observed. 6. On a reactive change in the pulp to the pulpotomy procedure employed or each medicament used, the most cases of High Positional Pulpotomy group showed that the reactive changed area was localized within the pulp, but the most cases of Low Positional Pulpotomy group showed that not only induration or degeneration already mentioned above, in an early stage, but also inflammation in the residual pulp occured within 20 days postoperatively and then, the inflammation infiltrated into the periapical tissues. 7. It was proved that the cases of Calbital and Calsan A out of the medicaments used in the present study were most favorable to healing of the wound residual pulp throughout the experimental groups of High Positional Pulpotomy and Low Positional Pulpotomy procedure and followed by N_2 and YOSHIDA Paste, but Triozinc Paste, Canals and Propac were unfavorable. 8. Although it is too hasty to apply the human cases from these results obtained in this present study, moreover, as an attempt to retain a residual pulp in the apical portion may give rise to seriously uncomfortable findings, which are the appearances of lesion of tissue and the subsequent extension toward the periodontal tissues due to the difficulty and instability of the subsequent filling procedure, it seems to be necessary that the pulp should be retained as much as possible on its volume in case of pulpotomy procedure and be removed completely to the root end in case of pulpectomy procedure.

抄録全体を表示

The deformation of a polysulfide rubber base impression material can be considered to appear as an effect of relief of the internal stress occurring during the gelation of the material, or of imperfect recovery from the strain applied to it during and/or after the removal of the impression. However, the mechanism of these phenomena have ever been scarecely elucidated. The author tried to make clear the deformation mechanism of the polysulfide rubber base impession materials used generally for precision impression in recent years. For this purpose, the author rehologically studied into the cause of the stress relaxation behavior from gelation process through relatively stable stage of reaction after gelation. Two stress relaxation tests were conducted : shearing test and tensile test. Principal results of the study are as follows : (1) Stress relaxation of a polysulfide rubber base imprssion material during and/or after gelation can be classified into the physical and the chemical relaxation within a low strain range permitting the fomation of linearity. The former is mainly due to the physical flow of the filler or the unreacted part. The latter is provoked by the network chain exchange reaction relieving the internal stress. (2) Physical relaxation may be explained by a simple Maxwell's relaxation. The chemical relaxation due to the network chain exchange reaction may be considered to follow a primary reaction. (3) In the initial stage of stress relaxation, the combination of physical and chemical relaxation is observed. However, it may be considered that the physical relaxation is completed in a relatively short time and thereafter only the chemical relaxation is observed substantially. (4) Permanent set (P.S%) of materials can be theoretically calculated on the basis of the continuous stress relaxation curve along with the discontinuous stress relaxation curve. The permanent set (P.S%) seems to depend upon both physical and chemical relaxation in the initial tension stage, while mainly upon the chemical relaxation in the later tension stage. This means that a respective increase in physical and chemical relaxation leads to the increase in permanent set. (5) As the gelation progresses, the network chain density increases and the chemical relaxation time is therefore lengthened. As a result, the decrease in fluidity of the contained filler results in the longer physical relaxation time. However, upon substantial completion of the gelation, the network chain density has a practically constant value, and so both physical and chemical relaxation present in a constant time. (6) The increase in temperature of a specimen results in the increase in exchange reaction rate and therefore promotes the relaxation. And then the fluidity of the filler also increases. As a result, the permanent set of the impression material increases.

抄録全体を表示

Many biochemical studies on the zinc and copper contents in the plasma of patients with malignant tumors and other diseases have been reported in the literatures. However, no definite conclusion has not yet been reached as to what changes could occur in the plasma zinc and copper contents in patients with malignant tumors, nor was there any report on the related subject in the field of oral surgery. The present author undertook to determine the plasma contents of both zinc and copper in 314 subjects suffering from a variety of disease including various types of malignant tumors. The trace metals were determined by use of atomic absorption spectrophotometry (Nippon Jarrell-Ash). In each determination of the metals a single sample of blood plasma was used. The plasma zinc level of the normal group was 1.14 ± 0.21 μg/ml, while the copper level was 0.95 ± 0.21 μg/ml. In the malignant group including 21 cases of malignancy in the oral region, the content of plasma zinc was 0.99 ± 0.22 μg/ml, and that of plasma copper 1.36 ± 0.30 μg/ml. The latter value was higher and the former was lower respectively than the corresponding values obtained from normal group with high significance (p<0.001). In an attempt to get an index of these two variables, the ratio of copper and zinc contents (Cu/Zn ratio) was calculated with all of the determinations. The result showed that the Cu/Zn ratio from the normal group fell in the range of 0.86 ± 0.14, while the one from the malignancy group rose to 1.43 ± 0.36. This difference in the indices between the normal and malignancy groups was statistically significant. It should be further noticed that 96.9% of the cancer group showed Cu/Zn ratio higher than 1.00, while only 9.8% of the normal group showed the ratio higher than 1.00, although 50.0% of the malignancy group demonstrated a lower level of plasma zinc than the normal rnge, and 77.6% of the group showed a higher level of plasma copper than the normal range. These indices tended to rise higher with progressive severity of malignancy. On the other hand, the Cu/Zn ratio higher than 1.00 was observed in high frequency not only in the group with malignancy, but also in groups of hepato-biliary diseases, renal diseases, appendicitis and pregnancy. Thus, those who gave the Cu/Zn ratio higher than 1.00 were not always limited to the group with malignancy. But the disturbance of the hepatic or renal function. Of course, the further study would be necessary to evaluate the Cu/Zn ratio from the viewpoint of cancer diagnosis. Nevertheless, it should be emphasized in the study of cancer metabolism that the cancer group in distinguished far more clearly from the normal group by the Cu/Zn ratio than by either copper or zinc level in the plasrna, and that the grade by the Cu/Zn ratio than by either copper or zinc level in the plasma, and that the grade of the advancement of the carcinoma was shown to have a close relationship with the ratio.

抄録全体を表示