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KMID : 0378019640070120061
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New Medical Journal
1964 Volume.7 No. 12 p.61 ~ p.108
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Anatomical Studies on the Alveolar Ridge, Dental Sacs and Tooth Germs in the Maxilla of the Korean Fetus.
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Abstract
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The alveolar ridge, the dental sacs and the tooth germs in the left maxilla of 535( a 286, S´ 249) Korean fetuses older than five month of fetal age were observed developmentally and anatomically and the conclusion was as follows:
1. Development of the dental sacs´ in the maxilla.
1) D6velopment of- the dental sac of the deciduous central incisor: During the fifth fetal month the transverse diameter was larger than the vertical diameter, and so the dental sac had the -semicircular form. As the fetal age progressed, the vertical diameter increased more rapidly´ and the dental sac shape changed to the elliptical, round form. In tenth month of fetal age the dental sac became transverse elliptical. The veatical and transverse diameters increased regularly as the fetal age progressed(Fig. 3).
2) Development of the dental sac of the deciduous lateral incisor: During the fifth fetal month the vertical and transverse diameters were almost same and-so the majority of the dental sac was round. As the fetal age progressed, the vertical diameter increased more rapidly and the dental sac elongated and became oval. The vertical diameter increased more rapidly after the eighth month of fetal age (Fig. 4).
3) Development of the dental sac of the deciduous canine: The tendency of the development was same as that of the deciduous lateral incisor(Fig. 5).
4) Development of the dental sac of the deciduous first molar tooth: During the fifth fetal month, they transerse diameter was larger than the vertical diameter and so the dental sac had a semi-circular form, thereafter changed to the transverse elliptical form. After the seventh month of the fetal age, on the upper border two projections, proximal and distal, came out, so it became peanut shaped. After eighth month of fetal age the vertical diameter increased more rapidly (Fig. 6).
5) Development of the dental sac of the deciduous secoud molar tooth : The tendency of the development was same as that of the deciduous first molar tooth. (Fig. 7)
6) Development of the dental sac of the first molar tooth: During the fifth month, the half of the cases was lacking and other half showed a swall dottlike form. After the seventh month it showed long elliptical, and after the eighth month it grew more rapidly (Fig. 8).
2. Development of the tooth germs in the maxilla.
1) Development of the deciduous central incisor germ: Through the fetal period the transverse diameter was larger than the vertical diameter. The vertical diameter increased regularly but the transverse
diameter increased slowly after the seventh month of the fetal age (Fig. 13),
2) Development of the deciduous lateral incisor germ: Before the eighth month of the fetal age, thet transverse diameter was larger than the vertical diameter, thereafter the traysverse diameter increased more slowly (Fig. 14).
3) Development of the deciduous canine germ : Through the developmental period, the vertical and transverse diameter were almost same and they developed regularly (Fig. 15).
4) Development of the deciduous first molar tooth germ: Through the developmental period, the transverse diameter was larger than the vertical diameter and. the transverse diameter increased more rapidly than the vertical diameter (Fig. 16).
5) Development of the deciduous second molar tooth germ: The transverse diameter increased more rapidly than the vertical diameter and the former was larger than the latter throughout the fetal period. Both diameters increased regularly (Fig. 17).
6) Development of the first molar tooth germ: After the seventh fetal month, it was measurable. The transverse diameter was larger than the vertical diameter and the former increased very rapidly throughout the fetal period. (Fig. 18)
3. Relation of the sizes of the tooth germ with the dental sac(Index)
1) The vertical diameter index: The indices of the anterior teeth were large and the indices of the molar teeth were swall. Before the eighth month of the fetal age they were larger(50-70%), thereafter they decreased (4065% )(Fig. 22).
2) The transverse diameter index: Before the eighth month of the fetal age, they were irregular, thereafter they decreased and converged to 7075% (Fig. 23).
4 The arrangement and position of the dental sacs of the maxilla.
The development of the dental sacs was more rapidly than that of . the maxilla, changes of the arrangement and position of the dental sacs were occurred.. During the fifth fetal month, the arrangement of the dental sacs was in one row, and was located in the medial part but as the fetal age progressed some of them moved out laterally and posteriolly and wrapped over.
5. The shape of the alveolar ridge of the maxilla.
In the fifth fetal month the alveolar ridge was low and had not a prominent projection and notch on its free border. As the fetal age progressed, there came out the projections on the central incisor part, the canine part of the alveolar ridge at first and then on the molar part. The alveolar ridge became higher, the notches between the dental sacs on the free border became prominent and the grooves appeared on the lateral surface.
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