Takahama A, et al. - The authors conducted this study to gauge the connection between the presence of the selected species/groups of bacteria in the apical root canal and expression of mediators of soft and bone tissue destruction in the lesions of apical periodontitis. They also probed the association between bacteria and other features of apical periodontitis. It was deduced that Actinobacteria possibly played a vital role in the active phase of soft and bone tissue destruction in apical periodontitis.