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KMID : 0352519810180020405
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Korea Univercity Medical Journal
1981 Volume.18 No. 2 p.405 ~ p.422
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Morphometrical and Histological Studies for Korean Primary Dentition
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손병화/Son, Byung-Hwa
徐英錫/Suh, Young-Suk
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Abstract
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The prenatal development, such as morphodifferentiation, calcification and morphometrics, on the primary teeth were analyzed in 116 Korean fetuses in age ranging from 6th week to the circumnatal period regardless the sexes.
1. Formulation of the epithelial band as the first indication of the teeth development was observed early at 6th week.
2. The primary- dental laminae could be recognized at the end of 6th week as a results of dividing of the epithelial band.
3. The enamel organs, of successive morphodifferentiation of the primary dental laminae, began to be developed in those of the primary anterior and 1st molar teeth by the end of the 7th week, those of the primary 2nd molars by the 8th week, and those of the permanent 1st molars by the 14th week, respectively.
~. The doubling of primary dental laminae and foundation of the enamel niche could be observed at the 9th week, and then their sizes and depthes were shown gradual increase until the 16th week. Those were clearly definable to be followed by a consequence of the changes of positions of the enamel organs and gums in response to the rapid growth of them.
~5. The permanent dental laminae of the anterior and premolar teeth were projected into the lingual side of the primary tooth germs by age ranging from 10th to 13th week, and those of the molars were projected distally without connection with the oral epithelium; that of the 1st molar by age of 11th week, that of the 2nd molar by age of 28th week and that of 3rd molar was not done before birth.
1.. The mean mesiodistal diameters of the maxillary primary incisors were not shown any racial difference, while that of the maxillary primary canines in Korean were measured smaller than those in the white and black.
2. The mean mesiodistal diameter of the maxillary primary Ist molars in Korean was, smaller than those in the white and black, and their mean buccolingual diameter in comparison with the mean mesiodistal diameter was slightly greater in Korean, but much greater in the white.
3. The mean mesiodistal diameter of the maxillary primary 2nd molars was not shown any racial difference, and their mean buccolingual diameter was smaller than the mean mesiodistal diameter in Korean, while this relationship in the white was shown the reversed figure.
4. The mean mesiodistal diameters of the mandibular primal; incisors in Korean were measured larger than those in the white, and that of the mandibular primary canines was not shown any racial difference.
5. The mean mesiodistal diameters of the mandibular primary Ist and 2nd molars in Korean were shown smaller than those in the white and black, and their mean buccolingual diameters in Korean were also much smaller than those in the white.
6. The mean mesiodistal diameters of the maxillary and mandibular Ist molars were measured as 4.83mm. and 5.25mm. at birth, respectively.
The rapid increment of growth in most of the primary tooth germs were measurable´ up to age of the 19th week, and thereafter decrement was progressively with the age. The highest range of the mesiodistal diameter of tooth germ was reached at 0.46mm. per week up to the 19th week, and was followed by those of the maxillary primary central incisor and the mandibular primary 2nd molar, respectively. The least range was calculated at 0.17mm. per week, and was follwed by that of the mandibular primary canine through the whole prenatal life.
1. Of the primary incisors the central cusps began to show the differentiation by 12th , y
to 13th week, and then the mesial and distal elevations of them by 15th to 16th I week.
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2. The single cusp of the primary canines was commenced into differentiation by about 14th week.
3. Of the maxillary primary Ist molar the mesiobuccal cusp could be detectable by 14th week, the mesiolingual cusp by 15th week, and then the other smaller cusps during 16th to 19th week.
4. Of the maxillary primary 2nd molar the first indication of the differentiation started from mesiobuccal cusp by 14th week, and those of the 2nd and 3rd cusp by 16th week, and then that of the last cusp by 18th week, respectively.
5. Of the mandibular primary Ist molar the mesiobuccal cusp was shown at 13th week,
the mesiolingual cusp at 14th week, and both of two distal cusps after ISth week.
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6. Of the mandibular primary 2nd molar the mesiobuccal cusp was observable at 14th week, the mesiolingual cusp at 15th week, both of the distobuccal and distolingual cusps at 16th week, and the distal cusp at 19th week, respectively.
7. The morphogenetic processes of the maxillary and mandibular permanent 1st molars´ underwent identical patterns as in those of the primary 2nd molars. It was shown only difference compared with those of the latter that the morphodifferentiation process of the former was succeeded within a quick term between 19th to 20th week.
1. The sequence of initial calcification of the primary teeth were maxillary central
incisor followed by mandibular central" incisor, mandibular lateral incisor, maxillary
Ist molar, maxillary lateral incisor, mandibular canine, mandibular 1st molar,
maxillary canine, maxillary 2nd molar and mandibular 2nd molar in successive
increase of prenatal age.
One of the sequential difference was taken notice that the initial calcification of the mandibular primary 1st molar was antecedent to that of the mandibular primary canine, whereas that of Korean´s was not.
2. The primary incisors began to calcify from the tip of the central cusp, and then that Nvas gradually proceeded mesially and distally over the lateral elevations in successive increase of the prenatal age.
3. The primary canines were calcified from the tip of the single central cusp by 17th week, and then that was proceeded radially in successive increase of the prenatal age.
4. Of the maxillary primary 1st molar, the mesiobuccal cusp was initiated on calcification at its tip by 16th week as same as those of the others, and then its proceeding Nvas gradually- decreased, and at the end of it the sequence was delayed about 3 weeks than that of the white.
5. Of the maxillary primary 2nd molar, the similarity on calcification could be noticed in comparison with those of the others, but that of the occlusal surface between the mesiolingual and distolingual cusps was not occurred completely in Korean ´Lwhereas was in that of the white.
6. Of the mandibular primary 1st molar, the initiation and proceeding of calcification were later than those of the other races, but that of the occlusal surface was occurred at the similar period in those of the others. That was understood for much narrow buccolingual diameter of it in comparison with that of the white.
7. Of the mandibular primary 2nd molar, the initiation and proceeding of calcification were slightly later than those of the other races, and thereupon that of the occlusal surface between the distobuccal and distal cusps was not calcified at the circumnatal period, whereas was in that of the white.
8. maxillary and mandibular permanent 1st molars began to be calcified only at the tip of the mesiobuccal cusp at the circumnatal period.
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