Alterations of non-collagenous phosphoproteins in human dentin coupled with the occurance of dentin hypersensitivity

本文研究了暴露牙本质过敏区牙本质小管和管膜的超微结构变化，管膜中非胶原蛋白的纯化及其特性。在同一牙本质表面的自然脱敏区，牙本质小管被超微或菱形晶体所堵塞，并观察到牙本质小管的矿化，提示牙本质小管上皮细胞膜的出现可能通过调控牙本质小管的矿化而与牙本质过敏的发生密切相关。为探讨肾小管膜的生理功能，进行了体外培养。从非胶原蛋白中纯化出骨连接素。我们还从人牙本质粉末中纯化了骨连接素。结果表明，牙本质骨粘连蛋白是一种高度磷酸化的唾液蛋白，其分子量约为23K道尔顿。牙本质骨连接蛋白对钙离子具有强烈的选择性结合作用，提示牙本质小管上皮细胞膜与牙本质过敏症的发生密切相关，牙本质骨连接蛋白可能通过钙离子的转运在牙本质小管的再钙化过程中发挥重要作用。

In this investigation, we have studied the ultrastructural changes of dentinal tubules and tubular membranes in hypersensitive area in exposed human dentin, the purification of noncollagenous proteins from tubular membranes, and their characteristics.The results obtained from the biopsy of hypersensitive teeth showed the opening of dentinal tubules and the appearance of tubular membranes in the hypersensitive area of exposed dentin.On the other hand, dentinal tubules were occluded with superfine or rhombohedral crystals in naturally desensitized area on the same dentin surface and the mineralization of the dentinal tubules was obseved in the area.These results suggested that the appearance of tubular membranes may be closely involved in occurance of dentin hypersensitivity through the control of remineralization of dentinal tubules.Extraction and separation of noncollagenous proteins from tubular mem-branes were carried out to investigate the physiological function of tubular membranes. An osteonectin was purified from the noncollagenous proteins. We also purified osteonectin from human dentin powder. It was shown that dentin osteonectin was highly phosphorylated sialoprotein more than other hard con-nective tissues and the molecular weight of it was 23K daltons. Moreover, dentin osteonectin was able to bind calcium ions strongly and selectively.In conclusion, the presence of dentin osteonectin in tubular membranes suggested that tubular membranes were closely related to the occurance of dentin hypersensitivity, and that dentin osteonectin may play important roles on the re-calcification of the dentinal tubules through the transportation of calcium ions.