The purpose of this study was to examine the effectiveness of instruction in tooth-brusing on oral cleanliness and improvement of inflamed gingiva in school-children. First, the oral condition was assessed in a group of 189 children, 14-15 of age, from three color photos of the maxillary and mandibular mirror images and a front view of mouth at the beginning of the study.
The children were divided three groups: (1) the oral condition was good, so it was not necessary to teach toothbrushing; (2) there was redness, swelling and bleeding of the papillomarginal gingiva, and dental plaque on the surface, so it was necessary to teach toothbrusing; (3) the oral condition was so bad that immedinical dental care was necessory. The second group of 82 were given individual instruction in brushing by a dental hygienist and a picture was taken of a front view of the mouth after 4 months. The oral cleanliness and improvement of inflammatory signs of the gingiva were compared in the color photos taken before and after the instruction.
The instruction resulted in a 50% reduction in inflamed gingiva. The instruction was repeated who did not show improvement.

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The present study was made to examine the effects of fluoride mouth-rinsing solutions on the enamel by X-ray diffractometry. Experiments were made in vitro of fluoride mouth-rinsing and fluoride topical application, with the powdered enamel as material; and the findings were compared. Phosphoric acid-acidified NaF solution (500 ppm of F^-; pH 5.0) was used as the fluoride mouth-rinsing solution, and compared with the acidulated phosphate fluoride solution (F: 0.9%; pH 3.6) for topical applica tion.
X-ray diffractometry was performed by the use of an automatic recording X-ray diffractometer to observe the crystallinity and identify the reaction products. For the observation of crystallinity, the half-maximum breadth (β^1/2) was measured, and the values calculated from Scherrer's equation were defined as the parameters of crystallinity. The reaction products were studied by identification with the A.S.T.M. cards, observation of alterations in the diffraction line profiles and peak shifts at diffraction angles of 50-54 degrees (20), and by the relative graph of sinθ-βcosθ by Hall's analysis method.
In the experiments of fluoride mouth-rinsing, the crystallinity was greatly increased, proving that a large amount of fluorapatite with considerably high crystallinity is produced. No CaF₂ was detected in the rinsing experiment, while a large amount of CaF₂ was produced in the topical application experiment, which shows that it is released with time.
From the findings described above, it has been shown that in the reaction of the enamel with fluorides, not only fluorine concentration but also the method of application influences the reaction products. In other words, it is suggested that repeated applications of a low concentration of fluoride by mouth-rinsing with a fluoride solution over a long period will produce fluorapatite with high crystallinity without decalcifying the enamel, and thus will exert a favorable effect on enamelapatite.

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This paper describes the effects of fermented milk beverages, “Yakult”containing live Lactobacilli (Abbreviation: LL beverage), and“Calpis”containing killed Lactobacilli (KL beverage), on caries in hamsters and rats.
Golden hamsters of NIH strain and Sprague-Dawley rats were used in the experiment. Microflora normally harboured in the mouth of the rodents were suppressed by providing penicillin in drinking solution for a few days before the experiment started. The animals, uninfected or infected with Streptococcus niutans K1-R, were reared on cariogenic diet #2000 and the beverages or deionized water as drinking fluid for 42 to 60 days. The raw or heat (100°C, 15min.) -treated LL beverage was used at original concentration, and the raw KL beverage at 5-fold diluted concentration. The diet and drinking solutions were continuously available. Molar dentitions of hamsters and rats were scored for dental caries by Keyes' method and the modified Takei's method, respectively.
Uninfected hamsters and rats produced almost negligible carious lesions, whereas oral infection of K1-R induced moderate caries in the rodents of control groups receiving deionizd water. When the animals were provided with raw or heat-treated LL beverage continuously for 60 days, caries extents of both uninfected and infected animals became much more severe compared with those of respective controls. Administration of KL beverage also induced severe caries in hamsters reared on the cariogenic diet for 42 days. The ability of both beverages to promote caries with various severities were also demonstrated by analyzing individually the caries scores of 3 molars of hamsters and 14 pit-and-fissures of rat's molars, which were shown to have various caries susceptibilities. The caries development of infected hamsters, however, were reduced to the extent of infected control by providing the beverages intermittently, 3 days and/or 1 day per week. These results clearly indicate that the continuous administration of the beverages promotes various types of caries with various severities in the rodents.
In addition, continuous administration of the beverages induced erosion-like lesions on the enamel of molar dentitions, particularly on the occulusal surface of 1st molar. The lesions might be caused by the highly acidic property of the beverages.
Experimental animals receiving LL beverage were significantly lower, but not the groups receiving KL beverage, than control animals in body weight gain and diet consumption.

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The properties of a calcium ion electrode (Orion Research Incorporated) were evaluated and the possibility of its application to medical and dental areas was studied. The electrode potential was affected by various factors; for example, the potential was increased by such monovalent cations as potassium or sodium, and by divalent cations such as magnesium. On the other hand, the potential was decreased by such anions as fluorine, phosphor and others. The decrease of the Nernst factor and the loss of linearity at a low concentration of calcium in the presense of those salts seems to be a characteristic trend of this electrode. Moreover, there were various other factors affecting the electrode potential: pH, ionic strengh, temperature of sample solution and others. In addition, variation from the normal potential is observed occasionally during repeated or continual use of the electrode.
Therefore, in calcium determination of biological samples containing many various salts andions, the adjustment of pH and ionic strength is an essential procedure, and also the other affecting factors must be taken into consideration.
It is possible to determine roughly the calcium content of the teeth if these affecting factors are taken into account. However, this electrode seems to be of limited usefulness because of the difficulty in adjusting these various factors.

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In the“Morinaga Dry Milk”incident, the affected infants were those for whom the powdered milk served as the main food and who were physically and mentally in the developing process.
In Osaka, an epidemiological study group was organized with several departments. In one section of it, a dental survey was made.
The results obtained were as follows;
1. DMF rate (97.57%) was above average (same age).
2. Tooth enamel hypoplasia was found to be much higher than average. Enamel hypoplasia of the anterior teeth was found most frequently, followed by the pre-posteaior teeth, and the posterior teeth, in descending order.
3. Prevalence rate of gingivitis was 41.46%. Melanin pigmentation of the gingiva was found to be 50.60%. and 71.43% of these cases had pigmentation in other areas of the body as well.
4. Regarding the states of occulusion, the incidence of Aangle II was 27.27% and of Angle III 26.83%.

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The effect of chlorhexidine (CHX) -containing dentifrice on bad breath suppression was determined. In the in vitro test, reacting the dentifrice with the mixed saliva, we measured sulfur compounds. The amount of sulfur compounds of the CHX-containing dentifrice group was low, and this result was statistically significant (p<0.01). In the clinical test in which the subjects used each dentifrice continuously for four weeks, sulfur compounds of the CHX dentifrice group were reduced by 51.8%. Moreover, the rate of debris suppresion in the CHX dentifrice group was higher than in the control dentifrice group.

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