In a survey which is based on the questionnaire method, it is the general principle that negative questions are avoided. In the present study, however, the author used one affirmative and two negative questions of a sample of 379 primary school pupils concerning their likes and dislikes of 5 different foods. In a comparartive analysis of thses questions, responses to them were more or less similar but when the responses to the first, second and third questions were examined on an individual basis, some measure of difference was found between the first one and the latter two questions.
The general trend was that, when asked about oranges, chocolate, etc., which the children generally like, their responses ranged from“not either”to“do not dislike them”. When asked about the foods generally shunned by children, on the other hand, the responses ranged from“like them”or“do not like them” to“neither”in a great proportion of the children under study, the foods in this class being the carrot, leek, etc. As a result, their responses were unstable.
It is concluded from these findings that, by using a questionnaire in which the affirmative and negative questions are combined, we are enabled to grasp realistically the likes and dislikes of children about the foods.

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The compatibility of some fluoride solutions (0.2% NaF, 0.2% NaF-0.1M H₃PO₄, 0.2% NaF-0.1M H₃PO₄-1% Sn₂P₂O₇, 0.4% SnF₂., 0.4% SnF₂-1% Sn₂P₂O₇) with different components of toothpastes, and the fluorine (F) and tin (Sn) uptake by powdered enamel from these experimental toothpastes were investigated.
The results were as follows:
1) F and Sn uptake by insoluble abrasives from the above fluoride solutions.
When the fluoride solution was added to the insoluble abrasive, the loss of soluble F and Sn was rapid and very great to calcium pyrophosphate (Ca₂P₂O₇). However, insoluble sodium metaphosphate (IMP) and polyvinyl chloride (PVC) were less reactive.
2) Influence of toothpaste components except for the insoluble abrasives on F and Sn uptake by powdered enamel.
0.2% NaF-0.1M H₃PO₄ and 0.4% SnF₂ solutions containing toothpaste components (glycerin, CMC, SLS, Na-alginate, bentonite, and Na-saccharin), respectively, were applied to the powdered enamel. Uptake amounts of F and Sn were compared with the water solution treated enamel. It was evident that bentonite reduced F uptake from NaF-H₃PO₄ solution. Although other ingredients did not show appreciable reduction of uptake amounts individually, the solution containing all of the above ingredients reduced F and Sn uptake considerably.
3) The enamel uptake of F and Sn from the aqueous slurry of these fluoride toothpastes was much less than from the water solutions of these fluoride compounds. The fluoride toothpastes containing IMP abrasive afforded enamel much more protection against acid than the pastes containing Ca₂P₂O₇ abrasive.

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The purpose of this study was to examine the effect of sucrose upon the solubility of the dental hard tissues.
Enamel and dentine powder prepared from freshly extracted bovine teeth was suspended in the following 3 solutions, namely pH 7.5 tris-buffer solution (B), mol sucrose in solution B (S) and solution S autoclaved at 125°C for 1hr (CS). After 16 days incubation at 37°C, the amounts of Ca and P dissolved in each solution were determined. Solution S increased the solubility of Ca and P in dentine, but decreased it in enamel in comparison with solution B. Solution CS significantly increased the solubility of Ca and P in both enamel and dentine.
The free N-terminal groups in enamel and dentine incubated in solution B and solution CS for 16 days were determined by the use of Sanger's fluorodinitrobenzene method. No difference was found between the two solutions.
In tooth powder deprived of its organic components by extraction with ethylendiamine, in natural apatite powder and in lipid-extracted teeth powder, the solubility tests were carried out under similar experimental conditions.
The results indicated that the amounts of dissolved Ca and P were strongly influenced by the extraction of the lipid component.
In the caramelized sucrose solution, lactate, formate, acetate and pyruvate were found. Any one of these acids was able to decrease calcium ion concentration in slightly alkalized CaCl₂ solution.

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From the results of a study on fluoride-containing dentifrice which was carried out on a total of 1101 school children, we attempted to calculate the minimum number of subjects necessary to judge its preventive effect on dental caries. In the present study we used the results of dental caries appearing on smooth surfaces in two groups (a Na-monofluorophosphate group and a control group) of second, third and fourth grade children, because caries reducing effects in these groups were comparatively greater than in other groups.
It seemed that about 50 children in one group were sufficient in order to prove significance by means of the X² test (P<0.05) in this experiment, compared with the rate of cavities appearing on susceptible surfaces. However, when the X²₀ value was calculated for all cases in which one child was added or substracted in each group, it was anticipated that the reductions would not be significant (P<0.05) in one fourth or one half of the cases if the experiments were repeated many times. It was considered that for 95 cases to be proved significant by means of the X² test (P<0.05) in 100 repeated examinations, it would be necessary to have 60 or 70 children in one group. Moreover, it was presumed that one group would need about 150 to 180 children when the comparison was between children with increased caries and children without increased caries.

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TAKEUCHI proposed the epidemiological principles of dental caries attack introducing a mathematical formula in 1961. In this formula, the multiple factors involved in dental caries attack are classified and analyzed quantitatively: the rate of caries incidence could be expressed as functions of the factor (p) represented by the sugar consumption after eruption of the tooth, and of the factor (q) of susceptibility to caries by the morphological form of each kind of tooth, and of the factor (r) of the susceptibility to caries equally distributed among individuals.
This study was conducted to established a useful method for evaluation of acid resistance of the surface enamel in order to elucidate one of the factors involved in the above mentioned formula.
The agar plates used in this study were made of agar (0.5% weight/volume) and 0.1M lactic acid-sodium lactate buffer solution, pH 4.5, mixed together by heating in a water bath for 20 minutes and left standing for 24 hours to solidify in a glass vessel of 2mm in depth. Circular plates of 6.5mm in diameter were cut out and used for the experiments. Impacted third molars extracted at the clinic of oral surgery were collected and stored in 10% formalin. One hundred of teeth for the experiment were chosen from this stock samples. The surface of the enamel was polished with a slurry of pumice and glycerin and then washed several times with re-distilled water and dried at 50°C for 5 minutes.
The agar plate was placed on the surface of the enamel for 5 minutes. After application of the agar plate, the phosphorus dissolved from the enamel was estimated by spectrophotometric determination with molybdate-safranin.
Using the same teeth, a conventional window method was applied: 4×4 mm of enamel surface was exposed and the rest of surface was sealed with paraffin wax. The exposed surface of enamel was immersed in 10ml of 0.1M lactic acid-sodium lactate buffer solution, pH 4.5, agitated continuously at 37°C for 5 minutes or 30 minutes.
The results showed that in the agar plate method, the values of mean and standard deviation were 1.00μg and 0.38μg, respectively. The distribution of phosphorus dissolved from the enamel revealed a fairly normal distribution pattern. In contrast, the window method pattern did not show a normal distribution, namely, the peak of distribution was biassed to low phosphorus dissolved in each case of 5-minute and 30-minute application.
The amount of phosphorus extracted by the agar plate method was plotted against the amount of phosphorus dissolved in 5-minute and 30-minute application by the window method in order to examine the correlation between them. The result showed that there was a significant correlation between the amount of phosphorus of both methods (r=+0.570, r=+0.645).
It was suggested that the agar plate method devised for this study could be useful for clinical testing.

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This investigation was undertaken to evaluate acid resistance of the surface enamel in vivo by the agar plate method reported by TAKEUCHI and KAWASAKI in 1963.
The agar plate used in this study were made of agar 0.5% weight/volume) and 0.1M lactic acid-sodium lactate buffer solution, pH 4.5, mixed together by heating in a water bath for 20 minutes and left standing for 24 hours to solidity in a glass vessel of 2mm in depth. Circular plates of 6.5mm in diameter were cut out for experimental use. The surface of the upper central incisor was polished with a slurry of pumice and glycerin and then washed with re-distilled water and dried with compressed air. The plate was placed on the tooth surface for various periods of time to determine the effective time for application in vivo. After application, the phosphorus dissolved from the enamel was estimated by spectrophotometric determination with molybdate-safranin.
The subjects were 366 children chosen at random from 1, 036 pupils of the 4th grade (9-10 years old) of elementary school. Fortyseven children were subjected to the application of an agar plate for 5 minutes and 317 of children for 3 minutes.
In the case of 5-minute application, the mean value of phosphorus dissolved from the enamel was 1.87μg and the standard deviation was 0.39μg. For the 3-minute application, the values of mean and standard deviation were 1.60μg and 0.38μg, respectively.
The data revealed that the distribution of phosphorus dissolved from the enamel showed a fairly normal pattern. With these experiments, the possibility of evaluation of acid resistance of enamel in vivo system by means of the agar plate method devised in this laboratory was demonstrated.
Moreover, six female subiects aged 18-20 were studied to determine an appropriate time for in vivo application. The experimental times were set from one to five minutes for each analysis. The results showed that phosphorus dissolved from the enamel in these samples increased with increasing the time of application, notwithstanding the magnitude of acid resistance of individual enamel.
From the data in this study, the 3-minute application of the agar plate in vivo seemed to be the best, since it obtains enough phosphorus for analysis with a minimum of trouble to the patient and takes into account possible error in measuring the time.

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