Introduction to endodontic microbiology

Endodontics is that branch of dentistry that deals with the diagnosis and treatment of diseases and injuries of the pulp and periapical tissues . The objective of the endodontic treatment is to render the teeth free of its disease and restore to its proper form and function in a healthy state.

Most changes in pulpal and periradicular tissues are of bacterial origin. Since they play a major role in the pathogenesis of pulp and periradicular lesions a fundamental knowledge of endodontic microbiology is needed to understand . The historical perspective of endodontic microbiology begins with the observation of oral flora by Antony Van Leeuwenhoek, which he referred to as ‘animalcules’.

In 1890, W.D. Miller, the father of oral microbiology authored a book called ‘Microorganisms of the Human Mouth’ which became the basis for dental microbiology. He demonstrated the presence of bacteria in necrotic human pulp tissue.

In 1939, Fish described the reaction of the periradicular tissues to bacterial products and antigenic agents from the root canal. He recognized four distinct zones of reaction namely zone of infection, zone of contamination, zone of irritation and zone of stimulation. Of these various zones, microorganisms are confined to the zone of infection by the polymorphonuclear leukocytes. He also theorized that removal of the nidus of infection would lead to resolution of the infection which became the basis for successful root canal treatment.

The true significance of bacteria in endodontic disease was proved by the study done by Kakehashi et al in 1965.When the pulp and periradicular tissues of germ free rats were exposed to the oral cavity flora they found no pathologic changes. Whereas in conventional animals pulp exposures led to necrosis of pulp and periradicular lesion.

Thus the association of the microorganisms with the pulpal lesions was documented through various studies.The disease and the process of tissue destruction is a combined end result of the interaction between the organism (offenders) and the host system (defenders). Therefore it becomes important for the clinician or the dental student to know the cause and effect of microorganisms on the host defense mechanism. Also the characteristics enabling the microorganisms to survive or perish within the endodontic environment must be understood to improve one’s clinical judgement in the treatment of pulp and periapical infections.

Thus the fundamental reason for accurate identification of bacteria from root canals is to disclose bacteria or its combination that may be resistant to conventional therapy or causative of treatment failure.

For many years scientific documentation of this intimate causal relationship and microorganisms was not possible because of the difficulty in isolation and identification of the bacteria related to the disease. In recent years with the advent of improved bacteriologic techniques and cultivation of the microbiota associated with the endodontic infections complex nature of the infection is revealed. Once the in-depth knowledge about the microorganisms is obtained the clinician develops proper understanding of the measures to control endodontic disease process and to manage the patients. Another consideration with the study of endodontic microbiology is the control over cross contamination with the help of aseptic techniques like sterilization and disinfection and also, the protection of the dentist and the patient.

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