Pathways of Pulpal Infection

You will be surprised to know that in the oral cavity, there are an estimated 1010 bacteria consisting of more than 500 different kinds of micro-organisms and all seek a niche and nutrition. As long as the enamel and cementum layers are intact, the pulp and root canal are protected from invasion, but loss of these structures by caries, cracks or trauma opens an avenue for penetration of bacteria through the dentinal tubules, Do you know that the dentinal tubules range from 1 to 4 micron meter in diameter, whereas most bacteria are less than 1 micron meter in diameter? The list of the causes of pulpal injury is very exhaustive which you must have read in previous units.

Bacterial movement is restricted by the outward flow of dentinal fluid (pulpal pressure is 24-30 mmHg), odontoblast processes, mineralized crystals, and macroglobulins including immunoglobulins in the tubules. The dentine-pulp complex of the tooth may react in a number of ways to the presence of microorganisms, but irreversible inflammatory changes may ultimately occur with the development of an inflammatory front in the periradicular tissues causing a chronic periradicular periodontitis (Fig. 1). A potentially compromised pulp may present itself in a variety of ways, as mentioned above due to caries, surface tooth loss or injury. In each case you need to estimate the following points:

• What was the pre-existing state of the pulp? Sensitivity to hot and cold, sensitivity in tooth to touch,etc.
• What is the extent of the injury? Check whether the surfaces are involved with caries, what is the extension of caries etc?
• What is the degree of microbial contamination?

The root canal therapy is based on the rationale, whereby the root canal system is cleaned; chemomechanically shaped, and then obturated, which allows healing to take place. The objective is to reduce the microflora to a minimum, as it is not possible to get absolutely sterile root canal system and prevent recontamination, which usually occurs coronally. Basically you need to create an environment at the apex so that the healing of tissue occurs.

Chart showing defense and immune reactions