Abstract
Dental caries incidence and age effect were studied on individual permanent teeth in terms of DMFT found in a total of 16572 male and female pupils of public schools ranged in age from 6 to 14 years. The results are summarized as follows. 1. Comparison of DMFT and the rate of DMFT found in three residential groups of subjects, suburban, urban and isolated islet, revealed that both values were highest in the urban, followed by the suburban groups and lowest in the isolated islet group. Possible reasons for the difference may be searched mainly in the diet habits, especially difference in the kinds of foods usually taken, in the cooking procedures and relative amounts of sweets consumed. 2. There was not found any noticeable difference between three subject groups with regard to the caries incidence relative to age stage with 28 permanent teeth examined. The rate of DMFT for every teeth was highest in the urban group, foollowed by the suburban, and lowest in the isolated islet group. 3. Comparison of the age-linked caries incidence for every tooth between male and female, showed that the rate was higher in the female than in the male. However, the sequence in vhich every tooth on each jaw suffer decay with advancing age was found identical. The molars and premolars showed higher incidence in the lower than in the upper jaw, while the anterior teeth showed reverse trend. The firet molar showed decay at the rate of more than 13% a early as 6 years of age, which approached to 50% by the age of 14. Emphasis should be given to the need of dental care for the infants from the time directly after eruption of the permanent teeth. The first and second premolars in both jaws were likewise extremely susceptible to the post-eruptive decay, but the progress of the decay with age was not rapid. Early dental care is also indicated on these teeth. The most marked increase of decay with advancing age was observed in the seeond molars. These teeth should be under surveilance throughout the time to come against the decay.
