The Journal of the Kyushu Dental Society

In stead of the direct measurement of human head hitherto commonly used with some inconvenience, the author devised an apparatus for measuring photographycally the head within an error of 0, 5mm. A pair of reflecting mirror and a pair of prism positioned properly before the camera permit to photograph the head of seated individual simultaneously from both frontal and lateral side on one same 35mm. film. The eye-ear-plane of the subject must be kept horizontal meanwhile and a pair of scale are fixed near the head. The deviations of lengths resulted from the difference in plane between the scale and the object to be measured are known from the two-sided portraits to make necessary corrections by calculation. The deviation corrector makes it possible to eliminate the trouble of calculation and the actual lengths are readily legible on its scale. The largest error found for the full length of picture was 0, 9mm, in ordinary range of head measurement, however, it was 0, 5mm.

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Oral mastication is the initial process of digestion, a physico-chemical reaction comprising primarily the law of diffusion. According to the law, the amount of a certain substance dissolved is proportionate to the surface area of particles of the substance. The efficiency of mastication, therefore, may be most properly expressed by the increment in surface area of particles of the material chewed. On the other hand, there is in the field of engineering Rittinger's principle concerning crushing work and the surface area of solid that the amount of work done in crushing is proportionate to the increment of surface area of particles crushed. The authors undertook, therefore, to study experimentally as to whether or not this principle also holds true in the masticatory process of human mouth. 10 grams of peanut selected as a test material were allowed to chew 30 times in 30 seconds, then the products were sieved through 3, 4, 6, 8, 10, 14, 20, 28, 35, 48, 65, 100, 200 mesh sieves successively. Each portion of peanut particles was then dried and weighed, the surface area of which was then calculated respectively as shown in Table I. The results indicated that the number of chewing was in direct proportion to the increment in surface area of the particles. The author suggests that the masticatory efficiency of individual mouth be expressed by the increment in surface area of a test material as produced by definite number of chewing in definite time interval, and wants to call it R, Y, M (Rittinger-Yokota-Method), for the sake of convenience. The author deems that, though theoretically sound at the most, the method lacks as yet many substantiation for the practical application, and further elaborations are now demanded.

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Relation between pregnancy and tooth health was investigated on 1425 women being pregnant for four to six months. Caries indices and D. M. F. rates were examined in each age groop and on the base of birth frequency. The results were statistically analized and summarized as follows. 1. Tooth health declined with increasing number of pregnancy. 2. Gingivitis attributable to pregnancy was observed in 32 percent on the average, the incidence rate increasing with birth frequeny. 3. Decayed tooth augmented in proportion to the intensity of morning-sickness.

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The psychogalvanic phenomena associated with the patients' psychic agitation or physical pain during the routine course of operative dentistry were investigated by the aid of a capacity coupled amplifier and a electro-magnetic recorder specially devised by the authors. The apparatus made it possible to delineate autographically the psychogalvanic phenomena on the smoked paper of the kymographion in continuation. The subjects to be tested were selected from the patients visiting the Clinic of Operative Dentistry of Kyushu Dental College, the dental personells, the nurses and the students which totalled to 44. The results obtained are summarized as follows. 1. Pre-operative psychogalvanic phenomena In some patients pre-operative psychogalvanic phenomena were elicited as soon as they seated at the dental chairs. In these cases individual differences were noted in the wave height, wave duration and the number of the waves produced. The phenomena were not seen in dental peresonells and nurses who were fully informed of the procedures to follow or in those person who were quite self-confident or fully reliant on the operators. 2. Psychogalvanic phenomena due to pain The pre-operative psychogalvanic phenomena at the patients' early visits gradually diminished as the patient was accustomed to the routine procedures, and only the galvanic responses due to pain became apparent. Among the waves of psychogalvanic phenomenon elicited during multiple treatments involved in the field of operative dentistry, those elicited by tooth percussion, mild grinding of dentin, manipulation of hand-reamer, exploration of hypersensitive cervix or cavity, and those elicited in some cases of caluculus scaling, were low in height and slow rising, while those elicited by removing soft dentin from deep cavity, by cavity preparation accompanying thermal pain, and by exstirpation of devitalized or vital pulp, had short latent time and sudden change with big height, requiring an extended time interval to recover normal states. In general, the wave heights and wave durations, though elicited apparently for the same type of disease and pain stimulus given of the same intensity, failed to produce any uniform pattern in the different subjects. However, in the same individual, with increasing intensity of pain stimulus given, the latent time shortened, the wave height changed suddenly and the wave duration was prolonged.

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