It was around 100 years back that a dentist felt the need for a bacteriologic examination of the root canal. This snowball has since then been rolling and enlarging i.e., even to this day, we are learning and exploring about the endodontic microbiology.

But the first question that arises in every beginner's mind is

How did the bacteria get into the pulp at the first place?

 We'll, this is how

1. Bacteria can invade through dentinal tubules following a carious invasion (most common way)
2. They can invade the pulp following a traumatic exposure (root or crown fracture)
3. Bacteria have found their way into the pulp via another interesting pathway that is the periodontal tissue. Bacteria present in deep periodontal pockets can easily reach the pulp via accessory canals.

We know nearly a thousand species of bacteria reciting as normal inhabitants of our oral cavity. But the root canals are generally inhabited by anaerobic bacteria such as treponema, porphyromonas, fusobacterium, Prevotella etc.

These bacteria do not need oxygen and fetch their nutrition from the blood supply in the root pulp.

Now here is one interesting thing to note, the primary intra-radicular infections i.e. the first infections that occur after caries or trauma, occur because of gram negative anaerobic bacteria like Prevotella, fusobacterium and treponema. Remember that this infection bearing tooth has never been treated before. Now we manage these endodontic infections with root canal treatment. But more often than not, we see persistent or recurrent infections even after the root canal treatment. Don't you wonder why this happens even when the treatment has been done under appropriate measures and with fine technique. Well, let's find the culprit!

It is a very stubborn bacteria called E. Faecalis that is most commonly found in root canal failures. E. faecalis has specific characteristics that enable it to escape chemo mechanical instrumentation during root endodontic treatment. It has the ability to form biofilms and colonize in remote unreachable areas away from the main canals, such as accessory canals, apical deltas, and isthmuses, etc. It can derive rich nutrition even from residual tissue, human serum, and dead cells. In addition, E. faecalis uses different mechanisms to survive in harsh environments. These bacteria can survive without nutrition for a long period. It further invades the dentinal tubules and protects itself from the intra canal medications like calcium hydroxide and EDTA.

 Recent studies show that fabclavine, an antimicrobial agent, has a strong antibacterial effect against E.  Some even claim that the use of fabclavine-rich supernatant is effective against multidrug resistant E. Faecalis multidrug resistance, when used as an intracanal medicament.

We are on the verge reaching the other side, where this obstinate bacterium will no more be a problem!