No More Root Canals for Kids? Stem Cells at Work

The Atlanta Journal-Constitution, December 21, 2006

Scientists report that kids may be able to say goodbye to the dreaded root canal thanks to the promise of stem cells.

Allowing the young tooth’s stem cells to continue tooth formation, a new, less invasive treatment leaves the soft inner pulp undamaged.

"Removing infected tissue by root canal is invasive, and, by doing that, we stop the tooth's continuous maturation process and leave behind a child with a thin eggshell of a tooth that is weak and susceptible to fracture," explained researcher Dr. George, an endodontist (root canal specialist) and an associate professor with the University of Maryland's College of Dental Surgery.

Four cases of preteen tooth decay were treated by cleaning the infected tooth tissue but not removing it, leaving the pulp stem cells in place. These stem cells went on to help the teeth recover, regenerate, and mature into strong healthy teeth. Dr. George and his team reviewed these cases which were performed by Taiwanese dentists. The results of the review were are published in the December 2006 issue of the Journal of Endodontics.

Rather than controversial embryonic stem cells, the researchers stressed that the stem cells in question were adult stem cells that all adults and children possess. And rather than any introduction of externally derived stem cells, the root canal is based on the application of a bleaching substance involved with the cleaning procedure that they use as a substitute to traditional root canal treatment.

"By leaving the tissue and just removing the infection, we observed in these cases that not only are the gums healed and the children's teeth free from infection and abscesses but, most importantly, there is a stem-cell aided completion of the root formation and tooth maturation over time," George said.

His team focused on periodontitis, a common form of tooth decay. Deposits of bacterial plaque below the gum line that can lead to tissue and bone decay, exposure of tooth roots, rum recession, and eventual tooth loss, characterizes the condition.

To treat this condition, root canal is normally offered by endodontists. Located in the center of the tooth, and commonly referred to as “nerve” tissue, the removal of this infected soft tissue with dental instruments characterizes the root canal procedure. To prevent re-infection or the spread of bacteria to other areas, the hollowed-out pulp chamber that once housed the extracted tissue is then filled and sealed.

Removal of degenerated matter does not induce long-term problems. According to dental experts the excised nerve tissue is not critical to normal oral function once adult teeth have matured.

However, in children under the age of 16, nerve/pulp tissue is vital to the healthy development. From the time a tooth first appears, the adult tooth-maturation process takes approximately three years to complete.

Root canal can stop this process and boost risks for dental complications, fractures, and even facial disfigurement, in younger patients.

But George’s team knew that opposed to the pulp in adult teeth, maturing teeth are much richer in blood supply. Compared to the pulp in adult teeth, it also has a superior capacity to regenerate itself. This is because the stem cells within children’s teeth have the ability to generate into the material that forms "dentin" -- the tooth's principal connective tissue.

So, would periodontitis treatments that permitted stem cells to stay in position and do their vital work leave kids with stronger teeth?

In an effort to find out, George and his team turned to Taiwan. Four cases involving boys and girls between the ages of nine and 10 who were treated for disease between 1988 and 2000 were studied by the team.

The pulp chambers of the children’s problem teeth were irrigated with about 20 ml of 2.5 percent sodium hypochlorite by Taiwanese endodontists as an alternative to performing root canal. The chemical is often used as a disinfectant and bleaching agent.

Following the cleansing, a removable anti-microbial compound called calcium hydroxide paste was used to plug the dried tooth cavity. In order to preserve the affected tissue and avoid unnecessary extraction of helpful stem cells, the researchers avoided the use of invasive filling.

Until radiographic exams revealed full tooth healing and an absence of peridontitis symptoms, the process was repeated.

In all cases, the disease was halted and affected teeth grew to healthy maturity as follow-up exams carried out for up to 5 years after the treatment revealed.

The only observed side effect was a narrowing on the root canal space and no complications ensued.

George and his colleagues conclude that an emphasis placed on encouraging a natural regenerative tissue process rather than getting in the way by using artificial filler materials, "strongly suggest a paradigm shift" in treatment of immature adult teeth. These types of techniques might even help in the treatment of adults’ teeth in the future.

"Of course, more research is needed to further improve the treatment by making it more predictable and laying down more detailed criteria for selecting those cases that have the highest chance to become successful," said George. "But clearly, this brings out greater awareness of the possible importance of stem cells for extensive clinical applications in the future."

Dr. Jim, chairman of pediatric dentistry at the University of California, Los Angeles said that, "it's clearly quite premature to suggest that you abandon root canals in these cases. And, obviously, more studies are needed to determine the parameters or contraindications of this procedure and to ensure a process for following the patient long-term. But, certainly, this is exciting and suggests great potential."

In a related study, a multi-national research team showed that in animal models they could successfully regenerated tooth root and supporting periodontal ligaments to restore tooth function.

The breakthrough holds promise for clinical application in human patients, said the researchers, headed by Dr. Songtao at the University of Southern California School of Dentistry.

In that animal models, the researchers created enough root and ligament structure to support crown restoration using stem cells taken from extracted wisdom teeth of 18 to 20 year olds. The resulting tooth restoration closely resembled the original tooth in function and strength.

Dr. Songtao said that those dental patients that would prefer living tissue derived from their own teeth or those who are no appropriate candidates for dental implant therapy would greatly benefit from this research.

The December 20th inaugural issue of PLoS ONE has published the findings.