We aimed to describe crown morphology of deciduous canines in modern Japanese people. The materials used in this study were extracted deciduous teeth from Japanese individuals comprising 46 children of which sex was already known. The observations have been made by plaster casts taken from the extracted teeth. Parameters for measurements were mesiodistal and labiolingual crown diameters, labiolingual root diameter, enamel bulge of cervical portion, crown height, mesial shoulder height, and CMSD (Cusp to Mesial Shoulder Distance). They were measured with digimatic sliding calipers with an accuracy of 0.01 mm. The deciduous canines were generally quite similar in morphology and size between male and female. Viewed from the lingual aspect, marginal ridges and basal tubercle of the upper deciduous canines were observed more frequently than those of the permanent canines. On the other hand, the spine and distal accessary ridge of the upper deciduous canines appeared less frequently when compared with the permanent canines. In the lower canines, ridges and grooves were weekly represented in phenotype as a whole. Odontometrically, the crown size was larger in females than in males. However, the sexual dimorphism was significant for only the mesiodistal and labiolingual crown diameters of the upper deciduous canines. The three indices of crown proportion did not differ significantly between the two sexes. Compared with the permanent canines, the deciduous canines were characterized as follows: 1) the crown index was smaller than 100, showing that the crown outline was elongated in mesiodistal direction in incisal view, 2) the enamel bulge of the cervical portion was relatively significantly thicker, 3) the mesial shoulder was located more closely to the cervical portion in the upper and lower deciduous canines.
The Super Science High School (SSH) consortium, in which high schools from various regions (Yaeyama Islands, Miyako Island, Okinawa Main Island, Saga Prefecture, Hyogo Prefecture, Miyagi Prefecture, and Aomori Prefecture) participate, have analyzed different Y-chromosomal and mitochondrial DNA (mtDNA) haplogroups from 2008 to 2012. In this study, we investigated the distribution of haplogroups in the above-mentioned areas. For Y chromosome, haplogroups DE*, and C1 showed higher frequency in the Ryukyu area (Yaeyama Islands, Miyako Island, and Okinawa Main Island) than in the Saga and Aomori Prefectures. However, haplogroup C3 showed lower frequency in the Ryukyu area than in Saga and Aomori Prefectures. Haplogroup O2b1 showed lower frequency in Okinawa Island, whereas haplogroups O2b* and O3 did not show any marked variability across regions. For mtDNA, haplogroups M7a and N9a showed higher and lower frequencies, respectively, in the Ryukyu area than in the Saga, Hyogo, and Aomori Prefectures. However, haplogroup N9b showed lower frequency in the Hyogo, Osaka, Kyoto, and Saga Prefectures than in the Ryukyu area and Aomori Prefecture. In conclusion, there seems to be a significant difference in the distribution of Y chromosomal and mtDNA haplogroups between mainland Japan and the Ryukyu area.
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