支台歯形成後の歯髄変化に関する光顕ならびに電顕的研究

Abstract

This study was aimed to investigate histo-pathological changes in the pulp of the dog incisors (240 teeth) after full crown preparation by light, transmission and scanning electron microscopy. The results obtained were summarized as follows : 1. Scanning electron microscopy revealed that dentinal tubules visualized by full crown preparation always contained torn dentinal fibers in the cutting surface of the dentin. This finding suggested that the initial changes of the pulp were caused by the direct damage to odontoblasts. 2. Changes caused by the preparation occurred widely in the coronal pulp, particularly in the pulp horn regions. These changes were dependent on the thickness of remaining dentin. 3. The recovery of odontoblast layer was observed at 3 days after preparation : Undifferentiated pulp cells were seen increasing their number at the site just beneath the odontoblast layer. Undifferentiated pulp cells located just beneath the odontoblast layer were observed to make contact with each other by gap junctions. These peculiar contacts were also observed frequently between this type of cells and odontoblasts. Further, similar cells were also found among injured odontoblast. It was suggested from the present morphological view points that these undifferentiated cells were precursor cells of odontoblasts and migrated into the odontoblast layer. 4. The reparative dentin began to form 7 days after preparation and increased its thickness gradually. The thickness of the reparative dentin was estimated to be about 40μm at the lingual or buccal side of pulp at 28 days after operation. 5. Matrix vesicle-like structures were seen in the predentin where newly formed odontoblasts aggregated. 6. The pathological changes in the pulp almost disappeared by 21 days after preparation. 7. Exposed dentinal fibers were still observed on the cutting surface even 28 days after preparation by scanning electron microscopy. Possibility raised from the present study that the pulp was still influenced by the oral environment through dentinal fibers even long period after preparation. For getting a good prognosis, the adequate post-treatments, that is, use of temporary crowns and suitable cements, seemed to be necessary.