A histological investigation into the actual conditions of infected regions of apices of the teeth with apical periodontitis

研究感染根管的根尖部位，不仅对阐明根尖周炎的发病机制有重要意义，而且对开展根尖周炎的治疗或诊断具有重要意义。因为感染根管的根尖区域可能是寄主和寄生虫的前线。因此，我们对患有根尖周炎的牙齿的根尖三分之一和根尖孔周围的根管外区域的细菌的定位和流行进行了免疫组织学检查。此外，我们还用扫描电子显微镜(SEM)观察了这些区域。在感染根管的根尖部位，以血吸虫、中间变链球菌、变链球菌、植物乳杆菌和乳杆菌居多；根外根管部位以植物乳杆菌、变形链球菌、中间假单胞菌和变种假单胞菌居多。植物乳杆菌在根尖外区的检出最为频繁，提示该菌在根尖周炎的发病机制中可能起重要作用。这些结果表明根管外细菌与根管内细菌在根尖周炎中的关系密切。扫描电子显微镜观察发现细菌聚集在根管表面的根外区域，与根管内细菌有关，这与免疫组织学观察结果一致。聚集在超基区域的细菌产生细胞外基质，并形成生物膜，阻止宿主防御系统消除寄生虫。这些发现表明，根管内细菌通过形成生物膜侵入根外区域，导致慢性病变，即根尖周炎。

To investigate the apical region of the root with infected root canal is important not only for the elucidation of pathogenesis of apical periodontitis but for the development of treatments or diagnosis of it. Because apical regions of roots with infected canal could be the front of host and parasite. Hence, we examined immunohistologically the localization and prevalence of bacteria in the apical third of a root canal and the extra-radical area surrounding an apical foramen of the teeth with apical periodontitis. Moreover we examined these regions by scanning electron microscopy (SEM). In the apical portion of the infected root canal, 5. sanguis, P. nigrescens/P. intermedia, S. mutatis, L. plantarum, and L. case/ were frequently observed, and in the extra-radical regions, L. plantarum, S. mutans, P. nigrescens/P. intermedia were frequently observed. In particular, L. plantarum was most frequently detected in the extra-radical areas; indicating this bacteria would play important roles in the pathogenesis of apical periodontitis. These results showed the close relationship between extraradical and intra-canal bacteria in apical periodontitis. SEM observations showed that bacteria aggregated in the extra-radical area on a root surface and were related to bacteria of the intra-root canal, which was consistent with immunohistological observations described above. The aggregated bacteria in the extra-radical areas produced extra-cellular matrix and formed biofilm that prevented host-defending systems from eliminating parasites. These findings indicate that intra-canal bacteria in the apical portion invaded and affected extra-radical areas by forming biofilm, which caused the chronic lesion i.e. apical periodontitis.