The difference in the dissolution of calcium was compared between extracted erupted first premolars (30 teeth) and unerupted first premolars (30 teeth). They were coated with parafin wax and two windows, 3mm in diameter, were made on the buccomesial and bucco-distal surface. One window was treated with fluoride and the other was used as a control. They were examined by biopsy 5 times during 30, 60, or 120 seconds using filter paper discs containing 2μl of 0.1M HCIO₄.
The dissolution of calcium from erupted teeth gradully increased with the passage of time whereas the dissolution from unerupted teeth was shown to reach a plateau after a few seconds.
The influence of fluoride treatment was more significant in unerupted teeth than in erupted teeth.
When the enamel surface was observed with SEM, a generally flat appearance was observed on erupted teeth. In contrast, a regularly arranged crater appearance was observed on unerupted teeth.
The observation that the reactivity of the enamel surface was higher in unerpted teeth than in erupted teeth suggests the existance of post-eruptive change (maturation) of the enamel surface of erupted teeth.

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1) The occurrence of caries in children (89 from the fluoridated area and 432 from the nonfluoridated area) aged 6-7 years with deciduous molars and in children (145 from the fluoridated area and 593 from the non-fluoridated area) aged 6-12 years with first permanent molars was examined.
2) Differences in df children and df teeth per child were not statistically significant between experimentals and controls. However, the proportion of children with large numbers (5-8) of carious deciduous molars was decreased.
3) No Differences in DMF children and DMF teeth per child were demonstrated. But the proportion of children who had C₃+C₄ teeth in DMF teeth and decayed teeth was decreased.
4) If the fluoridation had continued longer, the above results would have became more distinct.
5) Enamel hypoplasia was not clinically investigated in the present study.

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Public health is important in this country, but practical training in it is very difficult at the under-graduate level of dental school.
We tried a new teaching program under auspices of the several health centers in Tokyo for the training of students. Students listened to lectures from health officers about pollution, poisoning and other community problems.
They learned the examination method for 3-year-old children on the national health program, and they practiced the dental examination of these children. They had a chance to counsel mothers and children regarding dental health education. This training may result in significant changes in their public health mentality.

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