Microorganisms in periradicular tissues: Do they exist? A perennial controversy.

There is no greater association between the basic science and the practice of endodontics than that of microbiology. One of the strongest factors contributing to the controversies often encountered in the endodontic field is the lack of understanding that the disease processes of the pulp and periradicular tissues generally have a microbiological etiology. The vast majority of diseases of dental pulp and periradicular tissues are associated with microorganisms. After the microbial invasion of these tissues, the host responds with both nonspecific inflammatory responses and with specific immunologic responses to encounter such infections. The aim of this study is to fill the gaps in our knowledge regarding the role of microorganisms in endodontics and to discuss in depth whether their presence in periradicular lesions is a myth or a reality. An electronic search was carried out on PubMed database (custom range of almost 50 years) and Google using specific keywords and phrases. Inclusion and exclusion criteria were specified and around 50 articles were found suitable for inclusion. Full text of all the articles was retrieved and studied. Appropriate data were extracted and pooled and finally synthesized. It is important to understand the close relationship between the presence of microorganisms and endodontic disease process to develop an effective rationale for treatment.