We immunologically examined the prevalence and localization of 16 selected bacteria in the infected root canal systems and dentinal tubules of the walls of the infected canals. In this study, we established the new method which could maintain the canal contents during the preparation of the sections. This method was revealed to be useful to analyze the localization of selected bacteria especially in infected root canals.
All of the samples showed bacteria invasion in the root canals, however, only 70 % of the examined teeth showed bacterial invasion in the dentinal tubules. In the apical portions of the root canals, 75% of samples showed bacterial invasion. Streptococcus mutans was the most abundant bacteria detected in the Infected root canals. And S. mutans was the predominant bacteria in the coronal portions, Lactobacillus casei was predominant in the middle portions, and Streptococcus sanguis and Prevotella nigrescens/Prevotella interimedia were abundant in the apical portions of the root canals. Treponema denticola was scant in all parts of root canals. In the dentinal tubules, Fusobacterium nucleatum, Eubacterium alactolyticum, Eubacterium nodatum, L. casei, and Peptostreptococcus micros were abundant, whereas Campylobacter rectus, Actinomyces viscosus, and T. denticola were scant. Even in the canal-enlarged group, invasion of bacteria in the dentinal tubules was observed in 65% of the teeth. Analyzing the localization of the bacteria, the coronal third of the root dentin showed higher bacterial invasion than the apical third (p<0.05).
This immunohistological study revealed the actual condition of the selected bacteria in infected root canal and dentin. And this study also indicated that the canal-enlargement procedure could not completely remove all the bacteria in the dentinal tubules of the roots of teeth with infected canals.