PERMEABILITY CHARACTERISTICS OF DENTIN

牙本质代表了活的、敏感的、多孔的矿化区室 将牙齿中准备好的洞与下面的牙齿分开 纸浆 牙本质的渗透性特征是 了解牙本质敏感性和牙髓反应， 程序或材料。 牙髓刺激的空腔 准备可能是由于液体转移引起的牙本质 切割过程中的热或蒸发刺激。 拟议的实验 旨在测量这些流体移动的幅度， 它们有一个共同的分母，一个物理力（cm H2O）。 一旦 确定，这些力将被施加到空腔，以确定 临界物理力（负静水压力）， 在正常狗牙本质和牙本质中产生成牙本质细胞移位 用破坏成牙本质细胞微管的药物治疗。 的一部分 对腔制备的反应可能是由于神经源性炎症， 我们还计划测量牙本质流体流动的自发速率， 牙髓压力（PP）和牙髓血流量（PBF）在神经支配与 去神经狗牙齿后，正常洞准备，以检查 神经刺激对这些变量的影响。 在另一组 在实验中，PP和PBF将同时使用 血管扩张剂和血管收缩剂，以确定它们如何影响流体 在牙质中移动 最后，牙本质液将被物理迫使 在牙本质上（当牙冠就位时可能发生），以确定 对PP和PBF的影响。 一些牙髓刺激后看到洞准备可能是 这是由于作用在干燥牙本质上的毛细作用力。 我们将比较牙髓 对狗牙齿中正常洞制备的反应， 牙本质在盐水溶液中的残留物是无创伤的 这将阻止毛细力的表达。 其他牙齿将 受到轻度热和化学刺激， 目的 将在体外进行一系列实验， 具有上级涂抹层或粘性树脂以防止流体的牙质 转变发生。 最好的密封方法将用于 狗牙齿在体内，以防止流体引起的牙髓刺激。 在整个 在资助期间，我们收集的数据将用于开发一系列 导水率、扩散系数和渗透系数的数学表达式 对流流体向外运动与向内扩散相互作用 是否存在涂抹层。 这将允许 牙本质和牙髓牙本质复合体的计算机模拟的发展 这对世界各地的许多实验室都非常有用。 总的来说，这些实验应该提供急需的信息， 关于窝洞制备对牙髓牙本质复合体的影响。 结果将使我们能够提出一系列建议， 临床医生如何保护牙髓，避免牙髓发炎。

Dentin represents the living, sensitive, porous mineralized compartment that separates cavities prepared in teeth from the underlying dental pulp. The permeability characteristics of dentin are central to understanding dentin sensitivity and pulpal reactions to dental procedures or materials. Much of the pulpal irritation of cavity preparation is probably due to fluid shifts across dentin caused by thermal or evaporation stimuli during cutting. The proposed experiments are designed to measure the magnitude of these fluid shifts and reduce them to a common denominator, a physical force (cm H2O). Once identified, these forces will be applied to cavities to determine the critical physical force (negative hydrostatic pressure) necessary to produce odontoblast displacement in normal dog dentin and in dentin treated with a drug which disrupts odontoblast microtubules. As part of the reaction to cavity preparation may be due to neurogenic inflammation, we also plan to measure the spontaneous rate of dentinal fluid flow, pulpal pressure (PP) and pulpal blood flow (PBF) in innervated versus denervated dog teeth following normal cavity preparation to examine the influence of nerve stimulation on these variables. In another set of experiments, PP and PBF will be manipulated pharmacologically using both vasodilators and vasconstrictors, to determine how they influence fluid shifts across dentin. Finally, dentinal fluid will be physically forced across dentin (as may occur when crowns are seated) to determine what that does to PP and PBF. Some of the pulpal irritation seen following cavity preparation may be due to capillary forces acting on dry dentin. We will compare pulpal reactions to normal cavity preparations in dog teeth, to that done atraumatically in teeth were the dentin remains under saline solution that will prevent the expression of capillary forces. Other teeth will be subjected to mild thermal and chemical irritation for comparative purposes. A series of experiments will be done in vitro in an attempt to seal dentin with superior smear layers or adhesive resins to prevent fluid shifts from occurring. The best method of sealing will then be used in dog teeth in vivo to prevent fluid-induced pulpal irritation. Throughout the grant period, the data we collect will be used to develop a series of mathematical expressions of hydraulic conductance, diffusion and the interaction of outward convective fluid movement on inward diffusion in the presence or absence of smear layers. This will permit the development of computer simulations of dentin and the pulpodentin complex which should be extremely useful to many laboratories around the world. Overall, these experiments should provide much needed information regarding the effects of cavity preparation on the pulpodentin complex. The results will permit us to make a series of recommendations regarding how clinicians can protect the pulp and avoid pulpal irritation.