Study on the mechanism of idiopathic calcification in hard tissue of tooth

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This study was designed to inbestigate the mechanism of the defects of hard tissue formtion by traumatic injury to tooth term, to examine on the relationship between the timing of trauma and the defects of hard tissue formation after trauma. We gave experimental traum by penetration to tooth germs at different developmental stages, and examined traumatic changes and the degree of disturbance. Taruma before matrix formation of enamel (postnatal 1 day) produced localized defects of amelogenesis and we obserbed the defect of enamel locally with a SEM image. Irregular dentin was fromed and normal dentin formation was grandually repaired. In trauma at the early stage of enamel matrix fomation (postnatal 3 days), the defects of amelopeneses and irregular dentine formation with the formed hard tissue before ftauma occurred. In SEM findings, morphological change occurred in the cuspid and enamel hypoplasia was observed partially. Trauma at satge of enamel matrix formation (postnatal 5,7 days) … More affected the plural cuspids and the defects of hard tissue formation occurred at the tooth cervix. The surface of enamel wasrough with SEM image. At the same time, the crown of tooth germ was displaced or ankylosis at the cervix with the disturbance of eruption was seen. It was speculated that the canses for the appearance of these tooth cervix were due to be subjected to load of strees by trauma at the stage of matrix formation. Odontblasts were partly detached from dentin. Irregular dentin with cellular inclusions were distributed and dentin formed after trauma showed thickeing. Trauma at the stage of calcification induced a slight injury of hard tissue, but showed the defects of hard tissue formation at the tooth cervix in many cases. It was seemed that trauma at the same stage induced hypocalcification because enamel matrix remained partly.It's suggested that the degree and location of defects of hard tissue formation were different degending on the timing of trauma to the tooth germ. Less