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KMID : 0378019850280090143
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New Medical Journal
1985 Volume.28 No. 9 p.143 ~ p.154
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A Roentgenographic Study on the Root Development and the Change of Mesio-distal Tilt of Lower Third Molar with Aging in Korean
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Abstract
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This study was performed for the evaluation of the root development and the change of mesio-distal tilt of lower third molar with aging in Korean.
The dental standard roentgenographs of healthy 1, 102 male and 1, 158 female from 15 to 27 years of age were taken by paralleling technique.
The degree of root development was evaluated by Nolla´s method and the degree of tilt was measured with protractor, and were analyzed statistically.
The results obtained were summarized as follows.
1. One third of the root in length was developed at 15 years old, two thirds was developed at 17 years old, and the most gained full length at 19 years old beginning obturation of the apical foramen, and 93% of the subject gained complete obturation of the foramen at 27 years old.
2. The developmental rate of the root in the early stage seemed to be faster in the malethan in the female. But no sex difference was observed on the maturing period of the apical foramen.
3. The change of mesio-distal tilt with aging were as follows. In the 15 years old, more than one third of the subject was distributed around the inclination of 32.17°±2.630 against the long axis of second molar. Thereafter, it was gradually disappeared with aging. While, it made steady progress to divide into less mesial tilt and more mesial tilt group with maintaining the ratio 2/1. From the view of these changes, it is estimated that the tendency of distribution concentrating around the inclination of 32.170±2.630 would be more clear in the age less than 15 years old, therefore it is thought that the 32.170 ±2.630 is initial inclination of the lower third molar.
The bulk of the less mesial tilt group was concentrated near the parallel direction to the second molar and that of the more mesial tilt group was concentrated near 710~800 to the 2nd molar with aging steadily.
4. The tendency of mesial tilt was milder in the female than in the male in all the age groups.
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KEYWORD
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