Vital Pulpotomy in Young Permanent Monkey Teeth with Open Apices

活体未发育恒猴牙齿用氢氧化钙进行切髓准备。分别于术后0、6、9、12、24小时、2、3、4、7天用光镜和电子显微镜观察牙髓愈合过程中牙本质桥接情况，断髓后立即用氢氧化钙包扎，在离断端0.5~0.88 mm处形成一层坏死层。真正的变化包括细胞细节的丢失，血管充血和频繁的小出血。但是，受影响的地区后来似乎并没有扩大。6h后，牙髓浅层坏死组织内及其上方可见少量高度嗜酸性的小球体。9小时后，在凝结的血液和牙髓的坏死区有相似的小体。在超微结构上，凝血深层可见大量球形团簇和电子致密颗粒。在变性细胞内还观察到由细针状晶体和电子致密颗粒组成的球状团簇中的有机基质。然后聚集在一起，发展成粗大的颗粒，最后形成不规则形状的团块。7d时，成牙本质细胞样细胞已形成与细胞成分混合的胶原性纤维性牙本质基质。结论：本研究结果提示，在牙髓摘除后牙本质桥接过程中，凝血带、变性细胞和细胞碎片起着重要作用。

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.