Examination of the histological and bacteriological features of the interface between bacterial deposits and root dentin using a device that included exposed root dentin reproduced pulpal pressure in vitro.

本研究通过对离体牙本质标本和原位牙本质标本进行牙本质结构变化、牙菌斑和牙本质小管细菌定位和糖代谢变化的观察，并随着时间的推移进行动态观察。体外实验表明，变形链球菌和干酪乳杆菌混合培养的培养基的pH值低于单独培养的培养基的pH值。混合培养的牙本质小管中细菌感染的数量明显多于单独培养的牙本质小管。用过碘酸盐-硫代碳酰肼-银蛋白质酸盐-物理显影（PTSP）染色法检测细菌细胞内多糖的含量，证实大多数细菌细胞内存在大量的胞内多糖，这些多糖存在于牙本质表面附近菌斑层的小菌落中，并侵入牙本质小管。强制暴露表面和口腔环境仅两个月，细菌渗透到牙本质小管中是可见的，而在原位的十二个月的根表面样本中，一些微腔合并成指示更广泛的腔，但未观察到随后的牙本质破坏。套牙本质的存在可能是造成上述结果差异的原因。利用计算机图像处理技术，研究了牙本质破坏的时间依赖性，以及牙本质破坏过程中PTSP阳性细菌的定位和丰度的动态变化。

We evaluated structural change of the dentin and alteration of the localization and carbohydrate metabolism of bacteria in dental plaque and into dentinal tubules on the root dentin specimens in vitro and in situ, that we could observe with the progress in the time. In vitro experiments demonstrated that pH of the medium used for mixed culture with Streptococcus mutans and Lactobacillus casei was lower than it of the independent culture on a device which reproduced pulpal pressure by supplying the saline pressurized through dentinal tubules exposed in the pulpal side of root dentin specimens.On microscope analysis, the numbers of bacterially infected dentinal tubules in specimens used for the mixed culture was significantly more abounding than it of the independent culture. By periodate-thiocarbohydrazide-silver proteinate-physical development (PTSP) staining method, which could detect the intracellular polysaccharide in bacterial cells, it was clarified that much intracellular polysaccharide exists in most bacteria within which exist in microcolonies of plaque layer nearest the dentin surface and in which invaded into dentinal-tubules.On the other hand, in a root-dentin specimen, compulsorily exposed the surface and to the oral environment for only two months, the penetration of the bacteria into the dentinal tubules was visible, while in a twelve-month root-surface specimens in situ, some microcavities coalesced an indicated more wide-ranging cavities, but subsequent destruction of the dentin was not observed. The existence of mantle dentine was indicated as the factor by which brought about the difference of these results. It became clear to dynamically change in the time-dependent destruction of the dentin, which progresses on localization and abundance ratio of PTSP-positive-bacteria by means of image processing technology by the computer.