モルモット下顎臼歯の組織構造とその発生に関する研究
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概要
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The structures and developmental process of guinea pig's lower molar teeth were studied histologically using varying developmental stages from 30 fetal days to postnatal 7 days, new-born and adulthood. The results obtained were summarized as follows. 1. The cheek teeth, which were rootless and continued to grow as their occlusal surfaces were worn down, were compound teeth composing of three plates, mesial, distal and central plates. Each plate were covered with the enamel circumference of the dentin from occlusal to basal side, except only the lingual of them which was covered with the primary cement. There were stood between each plate the cartilage cement with which they were fixed strongly. 2. The periodontal membrane between the lingual cement and the alveolar bone showed structure similar to those of the rooted teeth. However, those between neighboring teeth showed characteristic construction to the present animals ; on the surfaces of the enamel there were distributed at almost regular intervals the cement pearls, from which the bundles of Sharpey's fibers were radiated and intersected with those of the opposite side from the lamina propria mucosae of the gingiva to the tip of the alveolar septum. On the surfaces of the enamel among the cement pearls there were arranged distinct layers of epithelial cells from the enamel organ of the basal portion to the oral mucosae, but their appearance varied depending on their location. 3. The Sharpey fiber bundles disappeared after the lapse of sudden loosing and resolving below the lamina propria mucosae of the gingiva. 4. The majority of germinal tissues in the basal end composed of large enamel organ occupied buccal and bilateral side, the dental papilla and dental sac surrounding them. As following toward the upper end, however, another small enamel organ was occurred within the lingual side of the distal dental papilla. Thereby, the distal dental papilla was divided into two parts. Large and small enamel organ were connected with only outer and inner enamel epithelium at the lingual side of the dental papilla. This connection portion were disappeared presently, and then replaced with dental sac, instead of them. 5. The mesial plate was made of the mesial portion of large enamel organ and the mesial dental papilla, the central and distal plates were made of the distal portion of large enamel organ, small enamel organ and two divided distal dental papilla, respectively. As following toward the upper end, the central portion of large enamel organ and small enamel organ were replaced with the dental sac from which the cartilage cement were formed. 6. The cartilage cement was derived from the growth of the cartilage cement pearls, and the cartilage cement pearls were based on the cement pearls. The cell nucleus of the cartilage cement showed almost necrotic degeneration. 7. Each molar teeth were developed with conical two cusps, but at the tip of the cones enamel formation did not take place. By reason of occlusion movement based on some physiological irritation, the conical cusps flattend at birth. Through thus attrition, the central plate became to appeared gradually between the mesial and distal plates. 8. The deciduous premolar showed crown shaped appearance with three cusps. There were seen at the tips of the cusps as free enamel area as the cusps of the molars. Conspicuous absorpting phenomenon was observed in the cervical dentin after 45 fetal days, without nearly forming their roots. 9. Order of these rooted and rootless teeth to erupt was as follows ; pm and M_1 (fetal 50 days), PM and M_2 (fetal 55 days) and M_3 (within a week after birth). By fetal 55 days, deciduous premolar came into shedding.
- 九州歯科学会の論文
- 1976-09-30