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By Joseph C. Stern, D.D.S.

“But Doctor, isn’t that a dead tooth?”

We often hear patients comment that a root canaled tooth is a “dead tooth.”  Is this true?  What are the issues at hand? If it’s not a dead tooth, how can we educate our patients a little more?  Let’s jump right in!

Inside-Outside Approach:

The fact is that a root canaled tooth is not a dead tooth or as some might call it, a dead organ. If this was the case the body would reject it much like it does any other foreign body. Root canal treated teeth are very much still a vital organ as it contains an attachment apparatus (periodontal ligament) that contains a rich supply of vital tissue. While the inside portion of the root canal no longer contains vital tissue, outside the root still maintains a rich blood supply. Periodontally compromised teeth have the opposite issue. They have a compromised blood supply outside the root but still contain vital tissue inside the root.  Interestingly, we never hear a periodontally compromised tooth called a “dead tooth” or a “dead organ.”

“But I thought there is no nerve in that tooth, how can it be causing me pain?”

Another comment we often hear from our patients.  In light of what we’ve explained thus far, we can explain why a previously endodontically treated tooth may cause pain.  A root canaled tooth is still very much a vital organ with a rich neurovascular supply coming from the attachment apparatus (PDL).  If bacteria gain entry into a previously treated root canal under a leaky filling or if the bacteria were never properly removed in the first place then this can trigger an inflammatory response in the surrounding periodontal tissue around the root. We call this apical periodontitis. Being that there is a rich supply of neurons in the surrounding tissues, this inflammatory response can trigger much pain. The pain the patient is experiencing at this point is in fact pain in the periodontal ligament surrounding the root.  In any case, the endodontically treated tooth is still a vital entity.

“I have an infection? But I don’t feel any pain!”

This one is bit more complicated to explain to our patients. To simplify, think of pain in a tooth being caused by an army of inflammatory mediators or an “inflammatory soup.” This soup of inflammation is activated and triggered by bacteria. Within this “soup” we have both pro-inflammatory mediators which trigger pain and tissue destruction, as well as anti-inflammatory mediators which block this destructive pathway. The balance between these two will determine the amount of ensuing pain and bone loss. This balance may shift from time to time depending on the strength and virulence of the offending bacteria versus the host resistance. Thus, there are periods where the patient can experience absolutely no pain.

Additionally, a patient’s unique genetic makeup plays a role in the nature of their inflammatory “soup,” some genomes being more destructive than others.

Lastly, and perhaps most importantly is the patient’s immune system. We all have different immune systems that will respond very differently to an inflammatory challenge. Some will respond better at blocking and nullifying the destructive painful process while other immune systems might fail to do so. A young, healthy person might respond significantly better to a bacterial challenge than someone who is immunocompromised.  There is a constant battle going on within each and every one of us. The ultimate winner of this battle reveals itself in the way we experience both pain and tissue destruction.

“Is it possible to rid an infected root canal of all bacteria? Isn’t the root canal space a complex labyrinth in which some bacteria might persist even after the most thorough cleaning? If some bacteria still remain, does that mean that ‘infection is left behind’?”

Our armamentarium today, including devices and chemicals, is so effective in reducing the bacterial population in the root canal space, that any residual bacteria is so depleted in virulence and numbers as to render them harmless. If some bacteria remain in the “nooks and crannies” of the root canal system, an effective coronal seal and apical seal wall them off from access to nutrition and the external environment, leaving them in a dormant, inactive state where they can no longer multiply and cause infection. This explains the high success rate that can be achieved with root canal therapy.

It all comes down to, “Location! Location! Location!” Because the environment in the oral cavity, much like the entire gastrointestinal system, which contains over 700 different microorganisms, can never be sterilized, we must look at periodontal disease and irritable bowel diseases as “Threshold” diseases, and thus we cannot speak of “Success”, but rather “Survival”. The doctor’s treatment along with the patient’s cooperation can maintain a healthy environment, but when the host’s immune system weakens or the bacterial virulence exacerbates, the threshold is breached and inflammation and tissue destruction will ensue.

“How can I have an infection in my lower tooth and still have pain in both my upper and lower teeth as well as all over the side of my face? How come I can’t seem to pinpoint the exact tooth that bothers me?”

How can we explain the complexity of localizing dental pain? Pain is a complex phenomenon. For one, the dental pulp is a richly innervated tissue that responds to specific stimuli and relays the message up to the brain. A closer look at this process makes it easier to understand why dental pain is so hard to localize. The pain pathway begins when nerve fibers within the dental pulp respond to inflammatory stimuli. This ‘detection’ takes place in peripheral tissues such as teeth or facial muscles for example. This message is sent to a relay station within the spinal cord for “processing”. From here the message is sent to the brain for ‘interpretation’. There are in essence three nerve fibers that carry the “pain message” to the brain. The noteworthy part of this process is that neurons from different teeth as well as many facial structures all pass through the same relay station as they make their way up to the brain. We have a hard time localizing pain because all these nerve fibers coming from different locations in and around the oral cavity converge on the same relay station within the spinal cord. The message that is ultimately relayed to the brain center comes from a larger receptive field (relay center) rather than directly from the one tooth. Thus, the exact location of pain is hard to pinpoint.

“Doctor, if we do a root canal, will that weaken my tooth?”

This is another question that we often get from our patients. The simple answer is that teeth that require root canal therapy often have previously undergone extensive decay or fracture. This loss of tooth structure inherently weakens the tooth, the root canal, does not. With the advanced technologies currently available, completion of a root canal can be done with minimally invasive techniques which preserves radicular dentin. We need to remind our patients that root canals don’t weaken their teeth but rather the decay or fracture that precedes their root canal does. Because of this the tooth should always be restored immediately after root canal therapy.

“But Doctor, why is tooth pain so severe? I’ve given birth before, but nothing comes close to this!?”

Tooth pain, like all other pain is caused by a combination of inflammation and tissue destruction. If the cause and effect of all pain is the same, why is tooth pain so much more intense? Once again, it is Location! Location! Location! The nerves and blood vessels (pulp) inside the tooth are encased in a confined and rigid space (root) that cannot expand to accommodate an inflammatory episode. This is called a “low compliant environment”.

To fully understand the concept of “low compliant environment”, we have to know the four cardinal signs of inflammation which are redness (rubor), heat (calor), swelling (tumor), and pain (dolor). When there is a buildup of inflammation elsewhere in the body, tissue expands (tumor) to relieve some of the intense pressure buildup caused by dilation of blood vessels to increase the flow of tissue fluid and inflammatory mediators into the area. Unfortunately the root cannot expand to accommodate this increased volume, and the pain from the increased pressure becomes intense. The only way to relieve this pressure is to initiate root canal therapy, allowing the pressure buildup to be vented out. In essence inflammation inside teeth has a malfunctioning inflammatory process, as one of the key features of inflammation is missing, “tumor”. The skull (brain cavity) is the only other low compliance system in the body, and here too, rapid intervention is needed to relieve the acute pain from the pressure buildup of a brain hemorrhage. Elsewhere in the body tissue can expand (swell) and inflammatory pain will subside to soreness and discomfort.

Hopefully some of these points can aid you in your communications with your patients. I tried to cover some of the fears that patients have expressed or keep internalized.

Dr. Joseph C. Stern is a Diplomate of the American Board of Endodontics. He is a Clinical Assistant Professor in Endodontics at Touro College of Dental Medicine and lectures frequently on the subject of clinical endodontics.  He has lectured at many local county dental societies, at the NJDA Annual Session in May 2019 and will be speaking at the Greater New York Dental Meeting in 2020. He maintains a private practice in Clifton, N.J.