上顎両側乳犬歯複根とその発生機序

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In primary and permanent dentition, canines locate between incisors and molars, and they are very important for the growth of occlusion and dentition. The number and shape are very stable, and they are interest in investigations of anatomical and histological abnormalities. The authors discovered a very rare case of bilateral primary canines with bifurcated roots and 2 supernumerary mediodenses in an 8 year 3 months old male. Two supernumerary teeth and bilateral primary canines with bifurcated roots were extracted at the exchange stage. These teeth were investigated in detail, anatomically and histologically, macro-and microscopically with a scanning electro-microscope. The developmental mechanism of the bifurcated roots observed in this study shows: 1. The crown form of the primary canines with bifurcated roots was simillar to normal primary canines. The roots of the primary canine bifurcated mesiodistally, were of the same length and each divided directly under the crown. 2. Compared with the measured values between the bifurcated canines and the normal single-root canine, the former were larger only at the mesio-distal diameter of the crown. Other teeth of this case were smaller than normal teeth. 3. In the histological study, the enamel of the primary canine with bifurcated roots and supernumerary mediodens frequently contained more numerous enamel tufts, abnormally shaped parazones of enamel prisms, and malformed or undercalcified enamel prisms. An interradicular crista and its related dentin nucleus or nuclei are found in normal multiple-root teeth, whereas neither the crista nor dentin nucleus were found in the primary canine with bifurcated roots. 4. In the root of the bilateral lower primary canines, there was a deep and large groove on the labial root surface. It was considered the lower primary canine roots showed a tendency to bifurcate. 5. In sucessive observertion with roentgenograms, the lower bilateral first and second premolar floar of the pulp-chamber were starting to calcify, and it is considerd that their roots will bifurcate. 6. Some enviromental factor in the early embryomental period occurred to bifurcate the upper primary canine root, and then to 2 supernumerary mediodenses, and sucessive lower premolar roots were bifurcated. 7. The enviromental factor influence continued from the early stage of formation in primary tooth buds to the stage calcifation of permanent tooth roots.
北海道医療大学の論文
1993-06-30

上顎両側乳犬歯複根とその発生機序

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