The cell surface substance prepared from Streptococcus mutans NCTC 10449 was used as immunogen, and its protective effect against dental caries was investigated in hamsters. The substance was administered with aluminium hydroxide subcutaneously two times before weaning. Hamsters immunized with this substance developed remarkably fewer caries on their molars than did hamsters sham-immunized, when challenged with S. mutans NCTC 10449. This preventive effect on caries development was associated with decreased recovery of bacteria from tooth surfaces, and saliva of immunized hamsters showed marked activity to inhibit adherence of S. mutans inoculated. These results suggest that the cell surface substance could be used as an effective immunogen against dental caries.

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The aim of the present study was to examine the differences in quality between maxillary and mandibular human deciduous teeth. Using the frontal deciduous teeth of Japanese, determination of the attrition, on the basis of newly designed standards, and of the microhardness for teeth which were spontanously dropped, revealed that the attrition of the maxillary teeth was higher than that of the mandibular teeth and that the microhardness of the maxillary teeth was less than that of the mandibular teeth. This finding may suggest some relationship between the trends of dental caries and these factors.

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Fluoride mouth-rinsing programme is widely spreading over districts where the fluoride concentration in the drinking water is low or the fluoridation of communal water can not be realized, as a relatively easy and effective method of inhibiting dental caries. The most commonly used fluoride mouth-rinsing solution for daily use is a neutral 0.05% NaF solution (225ppm F). The rationale for this concentration, however, is not so clear. It is necessary, therefore, to investigate whether a weaker fluoride solution would have sufficient cariostatic effect. If it does, we could select the weaker solution and practice caries prevention with more safety.
The present study was carried out in two elementary schools in the same district. The experimental group (school A) rinsed daily with a weakly acid (pH 5.0) sodium fluoride solution (100ppm F) at school under supervision and was given a routine school-based dental health administration. On the one hand, the control group (school B) was given the same dental health administration but without fluoride mouth-rinsing. The children of school A were instructed to rinse with 10ml of solution every school-day except Saturday, following the tooth brushing after lunch. Rinsing supervised by teachers was performed for 30 seconds (about 200 times per year). The dental examination was performed by trained dentists under standardized conditions as to light, mirrors, and explorers. The effects of rinsing were determined prospectively by comparing the dental caries experience of the children who had continuously participated in this study from the 1st to the 6 th grade, 79 children in school A and 63 children in school B.
The results of rinsing with the weaker solution showed significant inhibition of dental caries. After 6 years, the caries reduction in children of school A was about 50% in the mean DMFT, which was statistically significant (p<0.001). It was also observed that the fluoride mouth-rinsing confers superior benefits to smooth surfaces than to surfaces having pits and fissures, as previously reported. The cariostatic effect on the first molars was not so great as on other teeth.
To provide greater topical benefits for permanent teeth, therefore, it is necessary to start rinsing as early as possible. It may be considered that the age of 4 or 5 years is the time of choice in the beginning of rinsing. The results of this study suggest that fluoride mouth-rinsing with a weaker NaF solution is a practical and suitable method for school-based programs because of its efficacy and safety.

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For the prevention of periodontal disease, it is necessary to determine which age group to work with. We examined 927 patients who visited our clinic and measured the mobility of teeth with dental tweezers. The distribution of mobile teeth was analysed by age.
The results were as follows.
1. The prevalence of mobile teeth increased around 25 and 45 years of age.
2. An increase in the number of mobile teeth and a decrease in the number of non mobile teeth were observed between the ages of 30 and 45 years in 371 patients who had mobile teeth. Beyond 45 years of age, the ratio of the non mobile teeth showed no change, but the ratio of the mobile teeth decreased and the ratio of missing teeth increased with age.
These results suggest that young group below the age of 30 should be a target for the prevention of periodontal disease.

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The effects of fluoride mouthrinse (F: 500ppm, 5 times/week) and naturally fluoridated water (fluoride concentrations in drinking water: 0.3-3.2ppm) on fluoride uptake by deciduous enamel were investigated.
Fluoride mouthrinse increased the fluoride concentration at 1μm depth in enamel from 4, 300ppm to 7, 300ppm when the rinsing period was increased from 1 to 4 years. A statistically significant increase of the fluoride concentration, however, was not found at 5μm from the enamel surface. Therefor, fluoride uptake by mouthrinse was mostly restricted to the outermost enamel layers.
The fluoride concentrations in the deciduous enaml surface from a naturally fluoridated area are significantly higher than those in the enamel from a non-fluoridated area or enaml treated with fluoride mouthrinse. Extremely higher fluoride levels, approximately 10, 000ppm, were frequently found at 1μm depth in the surface enamel from high fluoride areas (over 1.0ppm). However, the enamel fluoride concentrations at 5μm depth from an area with 0.3ppm fluoride in the drinking water were not statistically significant compared to the control. High fluoride penetration found in the deeper layers of enamel in this study could due to both preeruptive and posteruptive acquisition of fluoride.

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Experimental evidence in a previous paper showed that the Ca/P ratio of the caries inducing diet showed a concave mode of caries inhibiting action, and the present paper confirms this by the finding that the largest amount of the Ca-phosphate sediment appeared at the most adequate ratio of Ca/P in the caries inducing diet, and that Ca-phosphate sediment lost this effect, but the sedimentation process degraded the nutritional value of a BHI broth for S. mutans, and caries inhibition induced by the sedimentation was not irreversible.

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Topical fluoride gel for caries prevention have been extensively accepted in clinical and public health programs because it is easy to apply.
Recently, the utilization of fluoride thixotropic gel has reported in several papers. However, the properties of the gel are still obscure. I have investigated the applicability of microcrystalline cellulose (MCC) as a gelling agent for fluoride application. MCC has thixotropic properties in itself, and is utilized in the food and drug industries.
The purpose of this study was to find a suitable thixotropic fluoride gel for its bioavailability and to assess fluoride release from the gel and fluoride uptake by enamel.
Experiments were performed to compare the physical and chemical properties of gels prepared in this experiment (EFG group: EFG-1-7) and commercial fluoride gels (CFG group: CFG-1-3). Experimental fluoride gels contain 5 to 7 percent of MCC as a gelling agent and 1 to 2 percent of sodium fluoride and other additives. As a conventional gel, two commercial fluoride agents (Fluorident gel and Gel II) were adopted and a fluoride thixotropic gel (Checkmate) was also compared with the EFG group.
For evaluation of physical properties of the gels, measurements were made of viscosity, thixotropy, adhesiveness, and adhesive residues of the EFG and CFG groups. To ascertain chemical properties, fluoride release and fluoride uptake by enamel were compared in the two groups.
The hysteresis loop of the gels as a thixotropic property was observed with a cone-plate rheometer. CFG-3 (Checkmate) showed a characteristic pattern of the loop and the experimental fluoride gel (EFG-7) also displayed an acceptable pattern. Experimental findings in regards to adhesiveness and adhesive resides showed that EFG-7 was superior to the CFG group in contact to tooth surfaces, in penetrating between the teeth, and in leaving a minium residue of the gel in oral retention.
Fluoride release of EFG-7 obtained 80 percent as much F^- as did the solution (APF) in the first minutes. In contrast to EFG-7, CFG-3 released only 0.2 percent fluoride.
Regarding fluoride uptake by enamel, mean fluoride concentration in teeth treated with EFG-7 was 21, 702 ppm (depth: 0.5μm) and 2, 405ppm (depth: 7.2μm), and that of CFG-3 was 2, 483 ppm (depth: 0.9μm) and 731 ppm (depth: 7.3μm).
These results indicate that the fluoride prepared in this experiment with microcrystalline cellulose has acceptable bioavailability with thixotropic properties, improving on the conventional gel and having greater fluoride uptake by enamel than the thixotropic gel of a commercial agent (CFG-3).

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Acidulated fluoride phosphate (APF) gel containing 2.2 percent sodium fluoride and 4 percent stannous fluoride solution were applied to the upper left first molars of Wistar rats. These molars were artificially exposed before the normal eruption time. The control molars were similarly exposed and treated with saline solution. These treatments were carried out before weaning. The rats were fed Diet #2000 and distilled water for 30 days after weaning. The incidence of dental caries was compared between the fluoride groups and the control group after killing the animals.
In prematurely exposed molars, two fluoride groups had fewer carious cavities than the control group, and they had no serious lesions, whereas the control group had many collapsible lesions. On ground sections, many fissures were decayed at the bottom in the fluoride groups, but were fewer than such fissures in the control group. When the fluoride agents were applied to normally erupted molars, the carious fissures were reduced.
The retention of fluoride and tin in the enamel surface was measured with an Electron Probe Microanalyzer (EPMA) on the molars of the rats which had been killed the day following topical application. An enriched zone of fluoride was observed at the entrance of fissure enamel, but at the bottom of the fissures fluoride was not detected. The values for detectable tin were similar to those of fluoride.
The retention of fluoride in the enamel surface of the APF gel group was measured by chemical analysis on the 1st, 7th and 10th days after application. Higher retention was observed in the molars exposed early than in those exposed later or in normally erupted molars.
It is concluded that the topical fluoride application was effective in preventing the destruction of the prematurely exposed molars.

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The purpose of this study was to investigate the relationship between dental caries prevalence in children and the personalities of mothers and children.
The subjects for the study 153 preschool children from 4 to 6 years of age and their mothers. At the oral examination, the caries of the children was classified into 4 types, O, A, B and C, according to the classification of the Welfare Ministry. The Yatabe-Guilford personality inventory and the Takagi-Sakamoto child personality inventory were applied for mothers and children, respectively. The data were analyzed by factor analysis.
The main results were as follows; 1. Four factors were extracted from the personal traits of mothers and children by factor analysis. These were the child's stability factor (Factor 1), the mother's passivity factor (F-2), the mother's instability-maladaptation factor (F-3), and child's sociality factor (F-4).
2. F-3 was shown to be related to the types of dental caries. This indicates that the prevention of dental caries in the children was more successful when their mothers were unstable and maladapted.
3. No correlation was found between F-1, F-2 or F-4 and the types of dental caries, though there might be need for further investigation as to the contribution of F-1.

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The purpose of this study was to assess the fluoride uptake by human enaml from dilute fluoride mouth-rinsing solution and the acid solubility of the enamel, by means of the window method and electron probe microanlysis.
Experiments were done in vitro by treatment with phosphoric acid-acidified NaF solutions (100ppm of F^-; pH5.0, 250 ppm of F^-; pH5.0) as the mouth-rinsing solutions. The fluoride content in successive layers of enamel was determined with an ORION ion meter and fluoride electrode. The calcium content was determined by atomic absorption spectrophotometry. An acid solubility test was used to determine the calcium released from enamel into a 0.4M acetate-sodium acetate buffer (pH4.0) every thirty minutes during a 3-hr period. Electron probe microanalysis was performed to determine the distribution of F, Ca, and P in fluoride-treated human enamel surface.
The fluoride content of human enamel increased with time. Especially the surface layer of enamel contained a greater amount of fluoride. The distribution of fluoride in enamel treated with the 250 ppm fluoride mouth-rinsing solution was greater than that of the 100ppm fluoride mouth-rinsing solution. The acid solubility test proved that the acid resistance was greater in fluoride treated enamel than in the control. Electron probe microanalysis showed that fluoride was taken up at the depth of approximate 60-90μm.
As a result, we suggest that the repeated use of dilute fluoride mouth-rinsing solutions over a long period will effectively prevent caries, .

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The measurements of cholinesterase (ChE) activity are widely used to evaluate of organophosphorus poisoning, but there are no reports about the effects of organophosphorus compounds on the function of the masticatory muscles.
I recorded the patterns of jaw jerk reflex (J.J.R.) in normal rats with a kymograph during the growth period and compared the changes of pattern in rats administered fenitrothion with the normal patterns. The significance of these findings was confirmed by their relation to ChE activity.
The results were as follows:
1) I was able to evaluate the function of masticatory muscles by the number of waves on the kymogram of the J.J.R..
2) Fenitrothion caused a decrease in the number of waves and disrupted the wave form.
3) There was significant correlation was observed between the number of waves and the ChE activity in red cells (r=0.72) and plasma (r=0.36) 1-1.5 hours after administration of fenitrothion.

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