Histological studies on the biocompatibility of tetracalcium phosphate-based cement

1.将磷酸四钙粘固剂和氢氧化钙粘固剂分别涂于大鼠上前牙裸露牙髓后1、3、7、10天，观察其组织学愈合过程。在使用氢氧化钙粘固剂的牙齿中，在新的硬组织形成之前，在粘固剂下面已经出现了坏死组织。相反，磷酸四钙粘固剂诱导了牙本质的形成，没有证据表明介入组织坏死或明显炎症。此外，在超微结构检查中，新形成的硬组织与材料直接接触。本研究表明4CP骨水泥具有良好的生物相容性，可作为直接盖髓材料。2.将新型磷酸四钙骨水泥(4CP)与新生大鼠颅骨细胞共培养，从光镜和电子显微镜水平研究成骨细胞对生物材料的体外反应。在测试材料的外围形成了复盖着活性成骨细胞的三维结节结构，其中包含一种矿化组织，其特征与体内形成的骨非常相似。在超微结构上，测试材料具有电子致密结构，并紧邻形态完整的细长细胞质突起或具有周期性结构的胶原纤维。此外，细胞外胶原基质的矿化直接发生在材料的表面。这些体外实验结果表明，4CP骨水泥具有与新生硬组织直接结合的特性。

1.Histologic healing processes were observed at 1,3,7, and 10 days after application with either tetracalcium phosphate cement or calcium hydroxide cement to the exposed pulp of the rat maxillary incisors. In teeth applied with calcium hydroxide cement, necrotic tissue was present beneath the cement before new hard tissue formed. In contrast, tetracalcium phosphate cement elicited a dentine formation with no evidence of either intervening tissue necrosis or marked inflammation. Furthermore on ultrastructural examination the newly formed hard tissue was in direct contact with the material. This study suggests that 4CP cement possesses a biocompatible property, which indicates its potential for use as a direct pulp-capping agent.2.Newly-developed tetracalcium phosphate-based cement (4CP cement) and cells derived from neonatal rat calvaria were cocultured to study the in vitro reaction of osteoblastic cells to the biomaterial at the light and electron microscopic levels. Three-dimensional nodular structures covered with active osteoblastic cells were formed in the periphery of the test material and they contained a mineralized tissue that exhibited features closely resembling bone formed in vivo. Ultrastructurally, the test material was circumscribed with an electron-dense structure, and was immediately adjacent to elongated cytoplasmic processes with intact morphology or collagen fibrils with periodic structures. Furthermore, the mineralization of the extracellular collagenous matrix occurred directly on the surface of the material. These in vitro findings suggest the propery of 4CP cement to bind directly with newly-formed hard tissues.