Vital Pulpotomy in Young Permanent Monkey Teeth with Open Apices

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The vital undeveloped permanent monkey teeth were prepared for pulpotomy with calcium hydroxide. The initial dentinal bridging during a postoperative healing process was examined at 0,6,9,12,24hr.,2,3,4 and 7days after operation by means of light and electron microscope.Sfter immediately dressing an amputated pulp with Ca(OH)_2, the calcium hydroxide produced a necrotic layer extending to 0.5-0.88mm apically from the amputation site. The ealist changes consisted of loss of cellular detail, engorged blood vessels and frequent small haemorrhages. But, the affected arears later did not appear to extend. After 6 hours, a few of deeply eosinophilic small spherical bodies could be seen in and immediately over the superficial pulp necrotic tissue. After 9 hours, in the necrotic zones of clotted blood and pulp there were similar bodies. Ultrastructurally a number of globular clusters and electron dense granules were observed in the deep layer of clotted blood. The organic matrices in the globular clusters apppeared to be composed of fine needle-like shaped crystals and electron dense granules were also observed within the degenerated cells. Thereafter, gathered togather developing to the gross granules, and finally formed irregulary shaped masses. At 7 days, collagen fibrous dentin matrix mixed with cellular elements was formed by odontoblast-like cells.In conclusin, the results of this study suggested that a zone of clotted blood, degenerated cells and cell fragments had some important role in initial dentinal bridging after pulpotomy.