Teeth are complex structures made up of multiple tissues including enamel, dentin, pulp and cementum. The crown of the tooth, the visible part above the gum line, is covered with enamel. Underneath the enamel is dentin, a bonelike tissue. The pulp contains nerves and blood vessels that supply the tooth with nutrients. At the root of the tooth is cementum, a bonelike substance that anchors the tooth in the jawbone via the periodontal ligament.
When a tooth is damaged from things like cavities or trauma, the pulp tissue inside can become irritated and inflamed, a condition known as pulpitis. Mild cases may resolve on their own but if left untreated, pulpitis can lead to more serious infection and abscess. One way to treat this is with a root canal, where the infected or inflamed pulp is removed and the inside of the tooth is cleaned, filled and sealed.
After a root canal procedure, the tooth is essentially “dead” as the living pulp tissue has been removed. While the remaining tooth structure can still function for chewing with the help of a crown restoration, the loss of the pulp tissue means the tooth can no longer sense hot or cold and it can become brittle and prone to fracture over time. For these reasons, there has been great interest in the possibility of regenerating or regrowing the pulp tissue in endodontically-treated teeth.
Can the pulp regenerate after a root canal?
After the root canal space has been filled, new living tissue cannot easily grow back in to repopulate the interior of the tooth. However, researchers have been investigating methods to intentionally regenerate or regrow the pulp tissue after root canal treatment. This has proven to be very challenging but some promising techniques have emerged.
One method is to attempt to stimulate and recruit stem cells from the apical papilla, which is found at the tip of the tooth root during development. In immature permanent teeth that have not finished growing, the apical papilla contains stem cells that play a role in the formation of root tissue. Some studies have extracted stem cells from the apical papilla in immature teeth undergoing root canal treatment. After disinfecting and filling the canal space, they have seeded a scaffold with these stem cells and placed it into the canal. Results showed some promising signs of pulp-like tissue regrowth.[1]
However, this technique is limited to cases with immature roots. In mature permanent teeth, the apical papilla and stem cell supply is no longer present. Researchers are investigating alternative sources of stem cells, including those that could be harvested from the patient’s own dental pulp or bone marrow.[2] These cells could then be seeded onto a biological scaffold and implanted into the prepared root canal space. Strategies to attract stem cells from surrounding tissues into the canal space are also being studied.
While pulp regeneration after root canal treatment has not yet become a reliable and mainstream therapy, ongoing research is making important strides. But currently, the pulp tissue cannot regenerate on its own after being removed through root canal treatment.
Can the roots or root tips grow back after trauma or fracture?
In some cases, the roots of a tooth may be damaged due to trauma such as a hit or blow to the mouth. If a tooth is knocked out entirely, there is no capacity for the roots to grow back. However, if the tooth root fractures but the tooth remains in the socket, root repair and regeneration may be possible under the right conditions.
The key requirement is that the pulp tissue must still be vital and healthy. The pulp contains specialized cells called odontoblasts that are responsible for laying down dentin, the bonelike material that makes up the bulk of the root structure. If those odontoblasts cells survive the trauma, they can help stimulate reparative dentin formation across a fracture line in the root.
For root regeneration to occur, the pulp tissue needs to be protected from bacterial infection. Therefore, root fractures in the coronal part of the root have the best prognosis, as the hard enamel layer provides a barrier against microbes. For fractures farther down the root, the pulp is more likely to become infected and require root canal treatment.
Even if pulp vitality is maintained, the periodontal ligament also plays a key role in root healing. The periodontal ligament contains progenitor cells that can help stimulate new cementum deposition along the fracture line. This cementum regeneration helps fuse the fractured root back together. Stabilization of the tooth fragments through splinting provides the best environment for optimal periodontal and cementum regeneration.[3]
While complete root regeneration does not typically occur, some fractured root tips have demonstrated repair with hard tissue formation across fracture lines. However, the regenerative capacity is limited compared to pulp regeneration in the canal space.
Can roots re-grow on deciduous (baby) teeth that are lost prematurely?
Deciduous teeth, also known as primary or baby teeth, are eventually shed and replaced by permanent teeth. The roots of deciduous teeth gradually and naturally resorb as the permanent teeth develop and push through the gums. But sometimes deciduous teeth are lost prematurely due to decay, trauma or extraction. This can disrupt the proper spacing for the permanent teeth.
In some cases, if a deciduous tooth is lost too early, the corresponding permanent tooth bud may erupt ectopically into the space left by the missing deciduous tooth. This malpositioning can lead to problems like crowding. For this reason, it’s ideal to maintain deciduous teeth for as long as possible until the permanent teeth are ready to erupt.
If a deciduous tooth is lost prematurely, it’s possible for the root structure to partially re-develop, allowing the deciduous tooth to re-erupt into the arch. This typically requires intervention to encourage regenerative growth, and success is variable.[4]
One technique is to expose the empty deciduous tooth socket and irritate the tissue to stimulate healing and development. Acidic preparations, lasers, or freeze-dried bone allografts have been used to irritate the socket tissues. In some cases, regenerative endodontic procedures similar to those used in permanent teeth may be utilized if pulp regeneration is also desired.
While research continues, regenerating lost roots on deciduous teeth remains a significant challenge. Maintaining the natural deciduous teeth for as long as possible until the permanent teeth are ready remains the best strategy.
Can bone and root fragments re-grow after extraction?
Tooth extraction involves removing the entire tooth including the crown and root structures. In most cases, this creates a socket wound that will completely heal over time as the bone regenerates and fills in the socket. However, sometimes tooth extractions are more complicated.
In difficult impactions or traumatic injuries, the roots may fracture into small pieces and fragments may be left behind in the bone. Similarly, small portions of the bony socket walls may chip or exfoliate during extraction. This typically occurs with extraction of larger multi-rooted teeth like molars.
When fragments of root tips or bone are left behind after extraction, they have the potential to heal via bone regeneration. The socket will attempt to fill in normally, and remaining root tips may fuse to the regenerating bone through cementum deposition or anchoring via the periodontal ligament. However, outcomes are variable and complications like infection are possible.[5]
Therefore, while small root tips and bone chips can sometimes re-integrate with healing bone after extraction, it is best practice to remove all tooth fragments and debride the socket of granulation tissue. This reduces the risk of future infection and complications at the extraction site. Leaving fragments behind should be avoided if possible during the extraction procedure.
Can lateral canals grow back after root canal treatment?
The root canal system consists of the main canal at the center of each root as well as many small branching canals, known as lateral canals. During root canal treatment, the goal is to clean and shape the entire canal system to remove all pulp tissue before filling and sealing the space.
However, because lateral canals are very small and difficult to detect, they often remain behind after cleaning and shaping procedures. These remaining lateral canals have the potential to allow bacteria to re-enter and re-infect the canal space, leading to treatment failure.
Researchers have looked for ways to stimulate renewed dentin formation in these lateral canals to cut off potential passageways for microbial recontamination. This could theoretically “grow back” the lateral canals via hard tissue deposition.
Some studies have shown tentative success using growth factors or stem cells to regenerate a dentin barrier at the orifice of lateral canals. However, the results have been inconsistent and it remains challenging to consistently locate and target the tiny lateral branches.[6] As a result, this regeneration technique is not currently reliable or in mainstream clinical use.
More realistically, lateral canals may be filled passively as sealer material is pushed deep into the canal walls during obturation. But active regeneration and growth of lateral canals after cleaning and shaping is not clinically achievable with current techniques. Thorough cleaning, disinfection and obturation remain the best methods to reduce risks associated with lateral canals.
Conclusion
While regenerating lost or removed tooth structures like pulp tissue, root tips or lateral canals is not currently achievable in a predictable manner, researchers are making important progress in this emerging field of regenerative endodontics.
In mature permanent teeth, the pulp tissue does not regenerate on its own after root canal treatment. However, some pioneering methods to intentionally regrow pulp show promise. Root tips or small root fractures may heal in a limited way if pulp vitality can be maintained, but outcomes are variable.
In deciduous teeth, regenerating resorbed or lost root structures remains challenging. The best approach is to retain primary teeth for as long as possible. Remnants of root tips or bone left behind after extraction have potential to heal but are best removed fully when possible during the procedure.
Though still in the early stages of development, techniques that aim to regenerate or regrow tooth structures could have a significant impact on restorative dental treatment in the future. However, at present such procedures are not considered reliable or mainstream therapies. Maintaining natural tooth vitality whenever possible remains the top priority.