Baseless claims linking root canals with cancer and other serious illnesses rely on outdated and long-disproven theories

On 1 November 2024, a Facebook reel with more than two and half million views claimed that root canal treatment, a dental procedure used to clear out tooth infections, leads to “diseases of the joints, brain, nervous system, and yes, even cancer”. Referring to root canal-treated teeth, it added, “97% of terminal cancer patients had this”. To support these claims, the reel cited research conducted by dentist Weston A. Price and oncologist Josef Issels in the first half of the nineteenth century.

Another post published on X (formerly Twitter) in October 2024 similarly claimed, “98% of women with breast cancer had a root canal on the same side”. In this case, the post cited a documentary called “Root Cause” as the source of the figure.

Claims linking root canal treatment with cancer and other chronic illnesses are pervasive online. Professional dental societies explain that such claims are baseless and potentially harmful, as they might deter people from receiving a necessary dental procedure. Currently, there is no scientific evidence that supports the claim that root canal treatment leads to disease elsewhere in the body.

This review will explain why these claims are false and how the myth originated.

What is root canal treatment?

Our mouths are populated with hundreds of different species of bacteria. Most of them are harmless and can even provide benefits like preventing the overgrowth of harmful microorganisms. However, poor oral hygiene and certain lifestyle factors can break this balance, allowing harmful bacteria to multiply and colonize the mouth. This can lead to dental problems such as cavities and gum disease.

Over time, cavities or injuries damaging the enamel, such as a broken or chipped tooth, may allow bacteria to reach and invade the core of the tooth, called the pulp. This causes an infection that can travel down the tooth through the root canals, which connect the pulp to the nerves and blood supply within the jawbone (Figure 1).

Figure 1 – Tooth anatomy. The visible part of the tooth, the crown, is covered by a hard material called enamel. Below, a layer of dentin protects the pulp, which is the core of the tooth and contains nerve tissue and blood vessels. The root canals run down the tooth, connecting the pulp with the nerves and blood supply from the jawbone. Source: MedlinePlus.

Although some tooth infections may go unnoticed, symptoms often include toothache, swollen gums, sensitivity to hot and cold, and bad taste in the mouth.

Good oral hygiene is the best way to prevent dental problems. But in the case of infection, a root canal treatment can help save a tooth that might otherwise have to be removed. This procedure involves drilling a hole into the tooth enamel to remove infected pulp at the root canal. The space left is then disinfected, filled, and sealed to prevent reinfections.

It is important to highlight that tooth infections don’t go away on their own and always require treatment. If left untreated, it may spread into other teeth, the gums, or the jawbone. Very rarely, the infection can travel further into the bloodstream and other organs, such as the brain and the heart, with potentially life-threatening consequences.

Root canal treatment isn’t associated with a higher risk of cancer

As we will show in the next section, the idea that root canal treatment causes chronic diseases is a myth that’s more than a century old. However, claims linking this procedure with cancer made a strong comeback thanks to the film “Root Cause”, directed by Australian filmmaker Frazer Bailey.

The central argument of the film is that bacteria supposedly left in root canal-treated teeth cause cancer, heart conditions, and other chronic illnesses. Based on this belief, the film advocated for tooth removal as the best way to deal with an infection.

To support these claims, the film relied on the testimony of several “experts”, including the well-known spreader of health misinformation Joseph Mercola. The list also included several individuals who define themselves as “biological” or “holistic” dentists. This isn’t a recognized dental specialty in the U.S., the U.K., or the European Union^[1]. Rather, it is an alternative discipline that frequently involves pseudoscientific practices. Also, some of the supposed experts involved in the film have faced disciplinary actions and allegations of malpractice.

Although the film was released on multiple platforms in 2018, including Apple, Amazon, and Vimeo, it didn’t gain much traction until it premiered on Netflix on 1 January 2019.

The film soon faced heavy criticism from academics and dental professional societies, which responded by publicly debunking the film’s claims. The American Association of Endodontists (AAE) even issued a guide addressed to its members that included tips to answer patient questions about claims made in the film.

On 29 January 2019, the AAE, the American Dental Association (ADA), and the American Association of Dental Research (AADR) signed a joint letter addressed to Netflix, Amazon, Apple, and Vimeo expressing their concern that the film could potentially harm the public by spreading claims that had “been disproven by decades’ worth of peer-reviewed, scientific evidence”.

The letter stated that the claim linking root canal treatment and cancer was a long-disproven myth:

“For example, in Root Cause, it is repeatedly stated that “97 percent of women who have breast cancer had a root canal tooth on the same side as their breast cancer.” This statement exploits the public’s fear of cancer and is not supported by medical evidence. The premise the film is based on dates back to research conducted in the 1920s which was later disproved because the original conditions for the experiments were poorly controlled and performed in non-sterile environments. Perhaps most importantly, other researchers have not been able to duplicate the results from the original experiment. Why portray information demonstrated to be incorrect as fact?“

In February 2019, The Guardian reported that Netflix had “quietly pulled” the film from its platform and “scrubbed all trace of it from their website”. At the time of writing, “Root Cause” remains available on Apple, Amazon, and Vimeo.

Despite the efforts to stop the spread of misinformation about root canal treatment, the claim continues to resurface on social media. In 2022, Carrie Madej, an osteopath known for spreading misinformation about COVID-19 vaccines, repeated the 97% figure in a viral social media post.

The truth is, there aren’t any studies showing that people with root canal treatments have a higher risk of cancer. In fact, the opposite was shown in a 2013 study published in JAMA Otolaryngology-Head and Neck Surgery^[2]. This study found that patients with multiple root canal treatments actually had a 45% reduced risk of head and neck cancer. Although the difference wasn’t statistically significant, these results directly contradict the claim that root canal treatment causes or increases the risk of cancer.

Multiple studies have also shown that poor oral hygiene, gum disease, and missing teeth are all associated with an increased risk of these types of cancer^[3-6]. This effect could result from a molecular mechanism linking poor oral health and cancer. However, it could also reflect an indirect association where oral health is a proxy for overall health and wellbeing, for example, the practice of healthy lifestyle habits or access to healthcare and early screening.

Furthermore, research conducted on large populations shows that people who had root canal treatments also had a reduced risk of death from cardiovascular disease^[7].

The origin of the claim

The belief that root canal treatment causes chronic illness can be traced back to theories that were developed in the 1920s. Weston Price, whom the Facebook reel cited, was one of its most prominent promoters.

In 1923, Price published the book Dental Infections, Oral and Systemic which discussed his studies on the “focal infection theory”. The theory affirmed that local infections are the cause of many chronic diseases. Specifically, Price claimed that root canal-treated teeth trap dangerous bacteria, causing infection and the release of toxins that ultimately trigger chronic diseases. Thus, he proposed tooth extraction as a method for preventing and managing these conditions. This is the basis of the claims made in “Root Cause”.

These ideas led to a wave of tooth extractions as routine treatment for a variety of conditions. However, this practice was abandoned in the 1950s, after newer and more robust studies disproved the focal infection theory.

In 1951, the Journal of the American Dental Association published a special edition reviewing published literature on dental management that shifted the standard of practice back to root canal treatment instead of tooth extraction. The review noted that Price’s studies “lacked many aspects of modern scientific research, including the absence of proper control groups” and used inadequate methods.

The origin of the claim linking root canal treatment to cancer specifically came later, in the 1950s. The 97% figure is typically attributed to oncologist Josef Issels, also cited in the Facebook reel. According to an article by Snopes, Issels allegedly reported that “in his 40 years of treating ‘terminal’ cancer patients, 97 percent of his cancer patients had root canals”. But claiming a link between canal root treatment and cancer based on this observation conflates correlation with causation, and is therefore incorrect.

In the absence of a properly designed study with adequate controls, no evidence indicates that having a root canal treatment and developing cancer are causally related. In other words, a vast majority of these cancer patients probably also ate apples or used soap, but this doesn’t mean that apples or soap caused their cancer. Instead, they are spurious correlations.

In 1961, Issels was charged and acquitted with fraud and manslaughter after three terminal cancer patients he was treating with alternative cancer therapies died.

Experts recommend preserving natural teeth over tooth extraction

Mo Kwan Kang, a professor of endodontics at the University of California Los Angeles, told The Guardian that tooth extraction can result in serious health consequences over time because it disrupts the jawbone’s original structure. This can impair the person’s ability to chew and make the jawbone more prone to fractures.

For this reason, saving your natural teeth whenever possible is the first option recommended by dental professional associations. The AAE explains that extraction is a traumatic procedure and is more likely to cause a leak of bacteria into the bloodstream than a well-conducted root canal therapy. However, in cases where the tooth’s structure is too damaged, extraction might be necessary.

In summary, if one wants to avoid root canal treatments, the best way is to prevent tooth decay and infection in the first place by practicing good oral care habits. The ADA recommends brushing your teeth twice a day with fluoridated toothpaste for two minutes, flossing between your teeth to prevent plaque, limiting sugary beverages and foods, and visiting your dentist regularly to check for oral health problems.

Conclusion

The belief that root canal treatment causes or increases the risk of chronic diseases like cancer is a myth with no scientific support. This claim relies on research from over a century ago that used outdated and flawed methodologies and whose results have been long-discredited.

Maintaining good oral care habits is the best way to avoid dental health problems. However, when an infection occurs, root canal treatment is a safe procedure that can save the natural tooth. This option is recommended over extraction because, unlike extraction, it maintains the original structure of the jawbone, keeping the person’s ability to chew and their natural smile intact.

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Dentist Grant Ritchey thoroughly debunked the claim that root canal treatment causes illnesses in an article for Science-Based Medicine titled “Pulp Fiction”.

REFERENCES

• 1 – García-Espona et al. (2023) European inequalities and similarities in officially recognized dental specialties. BMC Oral Health.
• 2 – Tezal et al. (2013) Dental Caries and Head and Neck Cancers. JAMA Otolaryngology-Head and Neck Surgery.
• 3 – Talamini et al. (2002) Oral hygiene, dentition, sexual habits and risk of oral cancer. British Journal of Cancer.
• 4 – Tezal et al. (2005) Is Periodontitis Associated With Oral Neoplasms? Journal of Periodontology.
• 5 – Guha et al. (2007) Oral health and risk of squamous cell carcinoma of the head and neck and esophagus: results of two multicentric case-control studies. American Journal of Epidemiology.
• 6 –Tezal et al. (2009) Chronic Periodontitis and the Incidence of Head and Neck Squamous Cell Carcinoma. Cancer Epidemiology, Biomarkers & Prevention.
• 7 – Meurman et al. (2017) Lower risk for cardiovascular mortality for patients with root filled teeth in a Finnish population. International Endodontic Journal.