In previous papers, Miura (Kuwahara), Fujimaki and Miura (Kuwahara) reported that the metabolic pathways of the genus Neisseria isolated from the oral cavity showed different patterns under various conditions. On the other hand, there is little reported about the bacterial substance of this genus.
In the present paper, we report a preliminary attempt to extract the crude bacterial substance.
The extraction of bacterial substance with carried out with the method of Takeda et al. using 0.3% diluted acetic acid solution.
The biochemical properties of this extracted substance was based upon the following three experiments.
1) Analysis of nitrogen, phosphate, reduced sugar and other reactions for the major component of this material is as follows:
N: 3.0-3.5%, P (total P): 1.0-1.5%, reduced sugar (as glucose): 20-21%
Biuret's reaction: ++, Molisch's reaction: ++
Elson-Morgan's reaction: +
2) For the protein estimation, the ultraviolet absorption from 220 mμ to 340 mμ was studied using a Beckman DU2 spectrophotometer.
The results showed a gentle absorption band at about 280 mμ for a 0.01 N NaOH solution of this material.
3) Electrophoretic analysis was also made according to the method of zone-thin-layer procedure by agar gel.
a) After zone electrophoresis, a 1 cm piece of the agar block was cut off and the protein fraction at 660 mμ was determined colorimetrically using Folin-phenol reagent. Two peaks were observed toward the cathode and one peak toward the anode.
b) On the other hand, the thin-layer method showed only one migrating band on the anode side using suddan-BB dye.
These results seem to indicate a lipopolysaccharide protein complex as the major component of this bacterial substance. Further details will be published later.

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Enamel surface changes caused by the topical application of fresh lemon juice were observed microscopically. Freshly expressed lemon juice was used, because tests revealed that the pH of the juice declines with the passing of time.
As a preliminary experiment, topical application of the juice was made on five extracted teeth, in this order: 1 min. application, 1 min. irrigation, and finally replica taking for microscopic observation. This procedure was repeated twenty times for each case.
One application caused no apparent changes on the tooth surfaces. Two applications caused changes in one tooth, and three applications caused changes in two teeth. All teeth showed some changes, more or less, after five applications. After seven applications, the enamel rod ends became visible in the whole microscopic field in all five teeth.
For experiments with living teeth, the following procedure was employed: 1 min. topical application and replica taking once a day for twenty days. The experimental group consisted of ten young males aged twenty to twenty-four, with normally healthy upper central incisors. The examinees led a normal every-day life, including meals and toothbrushing, except for the daily application of lemon juice. The application was continued on the left central incisor for ten days and observation by the replica method was made for twenty days. On the right central incisor, the application was performed until the enamel rod ends became visible in the whole microscopic field, and the replica was taken for twenty days.
The enamel rod ends became visible in the whole microscopic field after three or four days' application in both experimental groups. The changes occurred faster in living teeth than in extracted ones, and the changes after stopping the application varied from case to case. For instance, one showed disappearance of the enamel rod ends on the day after the application stopped, while another did not show any changes even ten days after the application ended.
Judging from replica observation, changes that appeared early in the experiment took longer to disappear than changes that appeared later.

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Tooth erosions occurred in a twenty-two-year-old female. The patient was healthy and had experienced no serious sickness, and the family medical history was normal. Her trouble was not caused by her occupation, because she worked as a bank clerk since graduating from high school. Her oral cleanliness was excellent. No dental deposit was present, because she had good habits from childhood, brushing her teeth well since her mid-teens. At present she brushes two or three times a day by the rolling method for an adequate period of time.
The girl did not recognize the erosions herself by pointing them out at her periodic health examination two years ago, nor has she recognized any symptoms since that time.
The erosions shown in the photographs are labial flat defects of the teeth from the upper right canine to the left canine. The dentin is exposed strongly except for 2-3 mm of enamel at the cutting edges from the upper lateral incisor to the left canine. The erosions of the lower teeth are slighter than on the upper teeth, although the teeth have become thinner, and the dentin is exposed on the left incisor and canine.
In replicas, dentin is seen clearly, and the enamel rod ends are seen also in the whole microscopic field on all parts of the enamel surface. There are also many scratches considered due to brushing.
we believe that the erosions are caused by the excessive eating of acid-containing citrus fruits, and are aggravated by too much brushing.

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In primary school, the prevention of dental caries with the use of fluoride offers various difficulties regarding equipment, the means of actual administration, time and expense. Using tablets for oral washing containing 1 mg of sodium fluoride per tablet, 116 school children between the second and fourth year were made to chew 2 tablets daily after their lunch for 1 year, after which the mouth was rinsed with water, as a measure for preventing caries.
Using 206 children in the same school year as controls, children of both groups were examined as to the state of carious invasion of the permanent teeth with DF (treated and untreated teeth) in comparison.
As a result, in children of each school year, the percent with DF in the upper and lower jaw, the average number of carious teeth per person, and the number of involved molar tooth surfaces per person increased in both the treated and control groups after 1 year. However, the increase was smaller in the treated group. In the ratio of DF teeth in the upper and lower jaw, an increase was noted in control children but a decrease was seen in treated children.
The ratio of caries inhibition in the DF teeth of treated children was calculated. In the average number of teeth per person in the upper and lower jaw, the ratio was 57.67% in the second school year, 55.63% in the third school year, and 34.62% in the fourth school year, giving a higher rate in the lower school years. However, in the average number of involved molar tooth surfaces per person, the ratio was 35.38% in the second school year, 52.83% in the third school year, and 53.33% in the fourth school year, giving a higher rate in the higher school years.
The present trial using tablets containing sodium fluoride for oral washing can apparently reduce expenses and omit the complex procedure of dissolving tablets in water. Moreover, an effect of caries prevention is obtained. This then appears to represent an effective method for preventing dental caries in children.

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The grammer school age is the period in which the development and prevalence of dental caries is most pronounced. A potent preventive measure for dental caries is therefore a vital need at this age.
In a primary school in Tokyo 211 school children ranging in age from 6 to 11 years were given a dental examination. These children had been given one fluoride tablet (1 tablet containing 0.5 mg sodium fluoride, 2, 500 I.U. of vitamin A, and 250 I.U. of vitamin D₂) daily along with their school lunch since their time of entrance into the school. As a control 484 children of the same age in the same environment as this group, but who had not been given this drug, were also evaluated. A comparative study of these 2 groups was carried out by dividing them into age groups, and calculating the F value. The following results were obtained.
In dental caries, number of DF teeth per child did not reveal a significant difference between the fluoride treated and control children, in each age group. However, number of DF teeth per child showed a significant difference above the age of 9, treated children showing smaller values than controls.
No significant difference was noted between the treated and control groups in the percents of children with tooth surface deposit periodontal disease, and malocclusion, in each age group.
These results would indicate that the administration of fluoride tablets in this way bring about a preventive effect on the development of dental caries after about 3 years of administration. This drug is therefore useful in the prevention of dental caries in primary school pupils.

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The purpose of this study is to elongate the effective period of the caries preventive sealing material chiefly consisting of Ethyl-2-cyanoacrylate (liquid) and Poly-methylmethacrylate (powder) developed by Takeuchi and others. Experimental materials were prepared by mixing the above-mentioned powder with varying kinds and amounts of glass filler, such as non-treated glass filler (borosilicate-glass powder), five kinds of silane-treated glass filler prepared by coating the surface of borosilicate glass powder with varying kinds of silane, and glass fillers prepared by treating first with Silane A-174 and then by solution-, suspension-, or bulk-polymerization with Methylmethacrylate (MMA). The effects of the addition of these glass fillers on the abrasion resistance, Micro Brinell hardness, compressive strength and water absorption of the sealing material were investigated, with results as follows.
1. The abrasion resistance, Micro Brinell hardness and water absorption of the sealing material containing non-treated glass filler were improved with the increase in the amount of glass filler.
2. In the sealing materials containing varying kinds of silane-treated glass fillers, the effect of the kind of silane on their physical properties was the highest in Silane A-187. Compared to the sealing material containing no glass filler, the sealing material containing 70wt% of glass filler treated with Silane A-187 showed approximately five times higher abrasion resistance, as well as improvements in the compressive strength, Micro Brinell hardness and water absorption.
3. In the sealing materials containing glass filler treated with Silane A-187 or Silane A-174, the effect of the concentration of silane treatment on their physical properties was approximately the same within the range of 0.05-1.0vol%.
4. In the sealing materials containing the glass filler treated with Silane A-187 or Silane A-174, the effect of the quantity of the glass filler on the physical properties was that in both cases all physical properties were improved with the increase in the amount of glass filler.
5. The effect of the method of polymerization of glass filler on the physical properties of the sealing material was investigated in the sealing materials containing the glass filler which was polymerized with MMA by varying methods after being treated with Silane A-174, with the result that solution-poly-merization was the best among the three methods.
6. Compared to the sealing material containing no glass filler, the one containing 70wt% of the glass filler which was treated by solution-polymerization with MMA after being treated with Silane A-174 showed abrasion resistance approximately six times higher than that of the control, as well as improvements in Micro Brinell hardness and compressive strength, and remarkable decrease in water absorption.
Furthermore, comparing to the self-curing resin containing no glass filler, its values showed remarkable improvements in the abrasion resistance, Micro Brinell hardness and water absorption, and were similar to the abrasion resistance and water absorption of the self-curing resin containing 70wt% of Silane A-174-treated glass filler.

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For the purpose of elongation of the effective period of the caries preventive sealing with Ethyl-2-cyanoacrylate and Poly-methylmethacrylate, it is necessary to improve the adhesion of the sealing material to the enamel surface. There have been reports on pre-treatment of the enamel with phosphoric acid as a possible means of improvement. However, because the enamel to he treated is a healthy enamel, it is necessary to give sufficient consideration to injuries that might occur to the enamel.
This study, therefore, was performed to obtain basic knowledge concerning solubility and adhesion of the enamel surface after the application of varying agent.
Materials and methods: Fifteen kinds of water soluble acid were chosen as agents, and solutions of seven concentrations of each agent were used in this experiment. The solubility was tested with the enamel tablets devised by the author and his co-workers, and adhesion tests were performed on the labial surfaces of extracted upper central incisors. Furthermore, electron-microscopical observation was made on the treated enamel surface.
Results: Solubility and adhesion of the enamel under the solutions of different concentrations of the same agent: both the solubility and the adhesion increased with the increase in the concentration, reached their peaks at a certain concentration, and turned to decrease with the further increase in the concentration, showing similar curves. It became evident that the greater the solubility of the enamel, the stronger the adhesion; likewise, the smaller the solubility, the weaker the adhesion.
In the cases of treatment with various kinds of agents, the relation between the solubility and adhesion of the enamel shows a remarkable variety, suggesting the existence of an agent which may combine minimum solubility and maximum adhesion of the enamel. It was also observed that the shape of the dissolved enamel surface had a great relation to its adhesion.

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It is desirable to elongate the effective period of the dental sealing with a resin adhesive, chiefly consisting of Ethyl-2-cyanoacrylate (ECA) and Poly-methylmethacrylate powder (PMMA). As part of a series of studies for the improvement of this point, the effect of using epoxy resin powder, instead of PMMA powder, on the physical properties of the sealing material was investigated.
Materials and Method: 1) Control material: The traditional composition made with ECA and PMMA powder (PMMA seal). 2) Experimental materials: Four kinds of compositions made with ECA and pulverized epoxy resin which had been polymerized with four kinds of curing agents. 3) Tetraethylene pentamine (TPA epoxy resin seal), b) Diamino diphenyl methane (DDM epoxy resin seal), c) Genamid 2000 (G2000 epoxy resin seal) and d) Hexahydrophthalicanhydride (HPA epoxy resin seal). 3) In order to observe the effect of each individual resin on the physical property of the sealing material, various measurements were made of the physical properties of PMMA and the above-mentioned four kinds of epoxy resin seals.
Results: 1) Bending: G2000 epoxy resin seal was 1.3 times greater than the control. 2) Flexural: All epoxy resin seals were smaller than the control. 3) Compressive strength: Every epoxy resin seal showed an improvement; in particular, TPA and DDM seals were 1.6 times greater than the control. 4) Micro-Brinell hardness: All showed similar results. 5) Abrasion loss: All epoxy resin seals were smaller than the control; in particular, DDM epoxy seal became 0.4 of the control. 6) Water absorption: HPA epoxy resin seal became 0.7 of the control. 7) Adhesion: HPA epoxy resin seal was equivalent to the control. 8) Marginal integrity: G2000 epoxy resin seal was better than the control. 9) None of the simple epoxy resin seals was superior to the control throughout the eight physical properties. In the synthetic evaluation, however, it was concluded that the physical property of G2000 epoxy resin sealing material was the best, TPA epoxy resin, DDM epoxy resin and PMMA sealing materials were similar, and HPA epoxy resin sealing material was the lowest in value. 10) With regard to bending, flexural, compressive strength, Micro-Brinell hardness and water absorption, the solubility of pulverized resin in Ethyl-2-cyanoacrylate seemed to have a stronger effect on these properties than the respective physical properties of the resin used as powder. 11) It was considered that in the case of epoxy resin sealing materials, (a) the above-mentioned physical properties of epoxy resin used as powder did not effect on these values so strongly as (b) the affinity of epoxy resin powder to ECA did in bending, flexural and compressive strength; (a) influenced more strongly than (b) in Micro-Brinell hardness and water absorption; while (a) and (b) worked equally in abrasion.

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