Down 症候群患者の歯の形態学的研究

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タイトル別名
  • A Study on the Tooth Crown Morphology in Down's Syndromes
  • A study on the tooth crown morphology in the Down's syndrome

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Langdon Down in 1866 first reported "Mongolism", which is later called Down's syndrome. Lejeune (1955) proved the chromosomal number of these patients to be 47 and termed it 21-trisomy. Although numerous reports have been made on the physical and oral characteristics of Down's syndrome, very few studies treat the statistical investigations on the tooth crown morphology with use of plaster models. The present author therefore made a dimensional and statistical investigation of the quantitative traits in crown morphology in a total of 61 subjects with Down's syndromes diagnosed clinically and cytogenetically and compared them with those of a total of 100 subjects who were devoid of the syndromes. The results obtained were summarized as follows : 1. Both the mesiodistal and buccolingual diameters were conspicuously inferior for Down's syndrome group as compared with those of the normal group. 2. The reduced rates of the buccolingual diameter than of the mesiodistal diameter were greater for the Down's syndrome group than for the control group. 3. The double shovel-shaped incisors were found in 4.3% in the upper central incisors (<I_1>___-) and in 7.3% in the upper lateral incisors (<I_2>___-), and the shovel-shaped incisors in 44.7% in <I_1>___- and in 38.0% in <I_2>___-. The occurrence was less frequent for Japanese and significantly less than in the normal group. 4. Caninization of lateral incisors in the Down's syndrome group was found in 50.9% in the upper jaw and in 43.8% in the lower jaw. The apperarance was more frequent than in the normal group. The distal accessory ridge found on the lingual surface of canine teeth appeared in 64.4% in the upper jaw and in 59.2% in the lower jaw. The appearance was less frequent in the syndrome group than in the normal group. 5. As to the cuspal types in the lower premolar teeth, 2-Type and 2 Type combined accounted for 58.3%, and 3- Type and 3 Type combined 41.7% in the first premolar teeth in the Down's syndrome group. The latter types were more frequent as compared with those of the normal Japanese. In the second premolars, there were no noticeable differences between the two groups. 6. Degeneration of hypocone in the upper molars of the Down's syndrome group accounted for 16.4% in the upper first molars, and 61.0% in the upper second molars with 3 Typs and 3- Typs combined. This degenerative tendency was more conspicuous in the syndrome group than in the normal Japanese. 7. Mesiodistally compressed crowns in the upper molars of the Down's syndrome group were observed in 7.3% in the first molars and in 48.8% in the second molars. These percentages were higher than those of the normal Japanese. 8. Carabelli cusps in the upper first molars occurred in 3.8%. The occurrence was less frequent in the Down's syndrome group than in the normal Japanese. 9. Dryopithecus pattern in the lower molars was seen in 45.3% in the first molars (<M_1>^^^-) and in 8.7% in the second molars (<M_2>^^^-), which were lower than those of the normal Japanese. 10. Protostylid in <M_1>^^^- occurred in 9.2% each, which was quite similar to that of the normal Japanese. Deflecting wrinkles accounted for 27.7% in <M_1>^^^- in the Down's syndrome group. This value did not differ much from that of the normal group. Occurrence of the sixth cusp was found in the 50.7% in <M_1>^^^- and in 26.8% in <M_2>^^^-, which were higher than those of the normal Japanese. The seventh cusp was found in 20.9% in <M_1>^^^- and in 8.7% in <M_2>^^^-, which were higher than those of the normal Japanese

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