Abstract
Replacement of temporary with permanent teeth was studied on 1020 male subjects and 920 female subjects, aged 6 to 18 years and living in Kitsuki city, Ohita Prefecture. Comparison was made with the data obtained respectively from groups of 307 males and 269 females aged 9 to 14 years and living in Kokura city, 159 males and 269 females aged 6, 9 and 13 years and living in Yoshitomi-machi, Fukuoka Prefecture, and also from groups of 2257 males and 1936 females aged 6 to 15 years and living in Kokura city as examined in 1950 by Ninomiya, the total numbers of subjects being 3743 of male sex and 3248 of female sex. The results were summarized as follows. 1) The average numbers of existing deciduous teeth as found in every subject groups examined were conveniently expressed in the following diagrams. Kitsuki city……Male>Female Kokura city……Male>Female Yoshitomi-machi……Male>Female Male……Kitsukicity〓Kokuracity Female……Kitsukicity>Kokuracity 2) The average numbers of erupted permanent teeth in the same groups were as follows. Kitsuki city………Male<Female Kokura city………Male<Female Yoshitomi-machi……Male<Female Male……Kitsuki city〓Kokura city Female……Kitsuki city>Kokura city 3) Average ages for deciduous tooth shedding in the same groups were as follows. Male in Kitsuki city………upper jaw>lower jaw Female in Kitsuki city………upper jaw>lower jaw Male in Kitsuki>Female in Kitsuki Male and Female………Kitsuki<Kokura (Ninomiya 1950) On viewing the average ages of deciduous tooth shedding in Kokura city and Kitsuki city from the data for the average numbers of existing deciduous teeth in both cities as examined in 1957, it was revealed that there was no difference in the average ages of deciduous tooth shedding in the male subjects of both cities, while in the female subjects of Kitsuki city the age was earlier than that in the female subjects in Kokura city. 4) The average ages for permanent teeth eruption were expressed as follows. Male and female in Kitsuki………upper jaw>lower jaw Male in Kitsuki>Female in Kitsuki Male and female……Kokura city <Kitsuki city (Ninomiya, 1950) On viewing the average ages for permanent teeth eruption as compared between Kitsuki and Kokura cities from the data for the average numbers of erupted permanent teeth in both cities, it was revealed that there was no difference in the male subjects in both cities while the average age for permanent teeth eruption for the female subjects in Kokura city was later than that for the female subjects in Kitsuki city.
