現代日本人の乳前歯についての形質人類学的研究
スポンサーリンク
概要
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Human deciduous teeth are said to retain much primitive morphology. This is quite a contrasting phenomenon with the fact that permanent teeth have much evolutionary morphology. With a view to elucidating primitive traces of deciduous teeth, deciduous anterior teeth were investigated for the present study. Maxillary and mandibular deciduous central and lateral incisors and canines were used and they were measured and examined morphologically. The results were as follows : 1. Almost no difference by sex was recognized in the measurements of the teeth. Significant difference was observed only in crown width and thickness of the maxillary deciduous canines. 2. Canine width index (ratio in crown width of maxillary deciduous canine to maxillary deciduous central incisor) was 100.8 This is an average value for the Japanese. This value is significantly smaller as compared with the Caucasians and reflects a racial difference. 3. Although shovel-shaped teeth are not as apparent as in the permanent teeth, they were found in 53.8% of the maxillary central incisors, 56.3% of deciduous lateral incisors, 47.4% of deciduous canines, and 55% of the mandibular deciduous canines. These are rather high rates of frequency as compared with the Caucasians and Negroid. This is regarded as a characteristic for the so called Mongoloid. 4. The extent of development of the basal tubercle was most significant in the maxillary deciduous canines and double tubercle in particular was found in 33.8% of them. 5. The marginal ridge was developed better in the distal marginal ridge than in the mesial marginal ridge. Among the deciduous anterior teeth, the extent of development of the marginal ridge was most significant in the deciduous canines for both jaws. Double-fold found especially in the mandibular deciduous canines showed a frequency rate of 15.2%. 6. The central ridge was most significantly developed in the maxillary deciduous canines, followed by the mandibular deciduous canines. The extent of development of the central ridge in the maxillary deciduous incisors was not quite high. 7. The frequency rate of appearance of the distal accessory ridge on the lingual surface of deciduous canines was quite high with 75.3% for the maxilla and 70.8% for the mandible. 8. The morphology of the labial surface showed no double-shovel-shaped incisors which are frequently observed in the permanent teeth. The labial surface showed comparatively bulged forms in many cases. This indicated that the central ridge was more developed on the labial surface as compared with other ridges. 9. The relations between the morphology of the labial surface and each of the physical properties of the lingual surface were examined with use of X^2-test and significant differences were found in : the maxillary and mandibular deciduous lateral incisors in the relation between the labial surface morphology and lingual surface basal tubercle ; the maxillary deciduous lateral incisors and the mandibular deciduous central incisors in the relation between labial surface morphology and the lingual surface central ridges ; the maxillary deciduous central and lateral incisors and the mandibular deciduous central incisors in the relation between the labial surface morphology and mesial marginal ridge.
- 九州歯科学会の論文
- 1983-04-25