The Research Of Status Of Bacterial Colonization In Infected Root Canal Of Different Oral Diseases

Purpose:To investigate the morphology, distribution and relative position of thebacteria in infected root canals with different oral diseases,including chronic apicalperiodontitis, severe chronic periodontitis and the combined periodontal-endodonticlesions.Materials and methods:Ten extracted roots with chronic apical periodontitis, andsevere periodontitis respectively, and seven with the combinedperiodontal-endodontic lesion were collected immediately after extraction, namedgroup A, group B and group C in turn. All clinical samples were rinsed in sterilesaline solution. The roots were split into two halves after cutting grooves along thetooth long axis. One half of the roots were examined for the distribution of bacteria inroot canals by Brown and Brenn-modified Gram staining with a light-transmittingmicroscope. The other half of the roots were examined for the occurrence of bacteriain the root canals by scanning electron microscopy.Results:Histobacteriologic observation showed that bacteria were found in rootcanals of different oral diseases.The frequency of occurrence of bacteria in threegroups was obviously different only in crown third and apical third of the main canal(P<0.05). Bacteria could penetrate into the inner part of the dentinal tubules about100-1100μm in infected root canals of group A, especially in the apical third. Forgroup B, the bacteria mainly penetrated into the outer part of the dentinal tubules inthe crown third of root canal about50-700μm. The distribution of bacteria in group Cwas less serious than the others, we found that the penetration depth of bacteria was about40-100μm in the inner part of the dentinal tubules. The result of scanningelectron microscopy (SEM) showed that the bacteria consisting of cocci, rods withamorphous materials formed the typical biofilm structure in the root canal walls, thedentinal tubules and intertubular dentin in group A. The SEM observation exhibitedthat the bacteria formed cluster or diffused on the root surface in group B. Theoutcome of group C was similar with group A, we found that the bacteria consistingof cocci, rods penetrated into the dentinal tubules, and the structrure of the dentinaltubules was destroyed.Conclusions:The differences of bacterial distribution were found between chronicapical periodontitis, chronic periodontitis and the periodontal-endodontic lesions. Thebacteria usually formed dense aggregates or biofilm structure penetrating the dentinaltubules in the apical third of the canal in chronic apical periodontitis; The bacteriamainly colonized in the crown third of the main canal in chronic periodontitis. All thefindings supported the view that the bacteria colonizing the dentinal tubules played asignificant role in the pathogenensis of different oral diseases.