Are Root Canals Safe? What the Evidence Says

If you’ve read that root canals are toxic, that they leave dead teeth full of bacteria, or that they’re behind illnesses elsewhere in the body, you’re not alone, and it’s a fair thing to ask about before someone drills into your tooth.

Here’s the short version. Most root canals do fine for decades without any problem. Some never fully heal. Both of those are true, and the second one doesn’t make the first one false. The useful question isn’t whether root canals are good or bad. It’s whether yours healed, and what to do if it didn’t.

Where the fear comes from

The idea is older than most people realize. In the early 1900s, the “focal infection” theory held that infections in places like teeth and tonsils caused disease throughout the body. It arrived at a time when germ theory was new and it seemed almost every illness might turn out to be an infection. Healthy teeth were pulled in the hope of curing arthritis and other conditions.

The dentist most associated with it today is Weston Price, who did experiments with extracted teeth in the 1920s. His methods were criticized at the time, and later, better-designed studies did not confirm his conclusions. The theory faded through the middle of the century as medicine began demanding better evidence.

It came back to public attention in 2019 with a documentary called Root Cause. After dental organizations raised concerns about its claims, Netflix removed it, and Amazon later stopped carrying it. A fact check by PolitiFact rated its central health claim false.

Gibbons RV. Germs, Dr. Billings, and the theory of focal infection. Clin Infect Dis. 1998;27(3):627-633. Pallasch TJ, Wahl MJ. The focal infection theory: appraisal and reappraisal. J Calif Dent Assoc. 2000;28(3):194-200. PolitiFact, November 13, 2019.

What’s actually true: some root canals fail

This is the part that often gets left out of the reassuring version, and it’s the part worth knowing.

A root canal removes the infected or dying nerve from inside a tooth, cleans the canals and seals them. But the canals are tiny, curved and branching, and bacteria can survive in places no instrument reaches. When a root canal fails, that’s usually why.

Those numbers vary a lot from study to study, and they include old root canals done to very different standards. Survival is a different measure from complete healing: reviews put tooth survival after a root canal at roughly 86% to 93% over two to ten years, with a crown afterward one of the strongest predictors of a tooth lasting.

Tibúrcio-Machado CS, et al. The global prevalence of apical periodontitis: a systematic review and meta-analysis. Int Endod J. 2021;54(5):712-735. Kirkevang LL, et al. Ten-year follow-up of root filled teeth: a radiographic study of a Danish population. Int Endod J. 2014;47(10):980-988. Ng YL, Mann V, Gulabivala K. Tooth survival following non-surgical root canal treatment: a systematic review of the literature. Int Endod J. 2010;43(3):171-189.

So the honest case isn’t that root canals never leave bacteria behind. Sometimes they do. It’s that a root canal that hasn’t healed can be seen, and something can be done about it.

Do root canals cause heart disease?

There is a real connection here, but it’s with infection, not with the root canal.

A systematic review of 19 studies found that most showed an association between infection at the root tip (apical periodontitis) and cardiovascular disease. The authors rated the evidence moderate to low and said a causal relationship couldn’t be established. In most of these studies, a root canal is simply a marker that a tooth was once infected. In one large study of male health professionals, the link with root canals was stronger among the dentists and essentially absent among everyone else.

Whether treating the infection lowers inflammation in the body has only been studied in small groups. Some found a drop in CRP, a blood marker of inflammation, and others found little change. Nobody has shown that a root canal lowers the risk of a heart attack, and we won’t claim it does.

Berlin-Broner Y, Febbraio M, Levin L. Association between apical periodontitis and cardiovascular diseases: a systematic review of the literature. Int Endod J. 2017;50(9):847-859. Joshipura KJ, et al. Pulpal inflammation and incidence of coronary heart disease. J Endod. 2006;32(2):99-103.

Do root canals cause cancer?

No study we’re aware of shows that root canals cause cancer. You may also see a claim that root canals lower cancer risk by 45%. That comes from a study of head and neck cancers in which the root canal result wasn’t statistically significant, so we don’t repeat it either.

Tezal M, et al. Dental caries and head and neck cancers. JAMA Otolaryngol Head Neck Surg. 2013;139(10):1054-1060.

Your health affects whether it heals

Healing at the root tip depends on more than the tooth. Diabetes is the clearest example. People with poorly controlled blood sugar have higher rates of infection at the root tip, and higher rates of root canals that don’t heal. The evidence is observational, but it fits what we see: the same infection behaves differently in different bodies.

Wang X, et al. The association between poor glycemic control and apical periodontitis: a systematic review and meta-analysis. Med Oral Patol Oral Cir Bucal. 2026;31(3):e465-e477. Observational studies.

Is pulling the tooth the safer choice?

Not automatically. Removing a tooth isn’t a clean, bacteria-free alternative: bacteria enter the bloodstream after most extractions, more often than after brushing. Implants have their own problem, an inflammation around the implant called peri-implantitis, which one review found in about one in five patients. And keeping your own tooth keeps the ligament that holds it in the bone and the natural feel of your bite, which no replacement fully matches. How the replacement options compare.

That doesn’t make removing a tooth wrong. When a tooth can’t be reliably saved, or when you’d rather not keep a root-canal-treated tooth, removing it and planning what replaces it is a legitimate choice, and it’s yours to make.

Martins CC, et al. Bacteremia following different oral procedures: systematic review and meta-analysis. Oral Dis. 2024;30(3):846-854. Diaz P, et al. What is the prevalence of peri-implantitis? A systematic review and meta-analysis. BMC Oral Health. 2022;22:449.

What we would actually do

• Confirm it really needs a root canal. Cold tests, comparing the tooth with its neighbors, and X-rays. How we decide, and why an endodontist does the root canal.
• Plan the crown from the start, because a leaky or missing seal on top is one of the main reasons root canals fail.
• Watch it heal. A tooth with a lesion at the root tip should be followed over time. When a 3D scan is needed, it’s read in full by oral and maxillofacial radiologists.
• If it isn’t healing, or the lesion is growing, decide what’s next: redoing the root canal, surgery at the root tip, or removing the tooth. That’s a decision made with the images in front of you and the endodontist’s opinion, not a reflex.
• Look at the whole picture, including blood sugar and other health factors that affect healing.

Worth bringing up

If you have an old root canal and you’re not sure whether it healed, or you’ve been told you need one and you have doubts, bring it up. We’d rather talk it through than have you put it off. Call 702-734-0776 or tell us what’s going on. If you’ve also read about jawbone “cavitations”, that has its own article.

Prevalence and survival figures are pooled across studies of very different design and quality, and can’t predict how any one tooth will do. Associations between infection and heart disease are observational and do not show cause. General information, not a substitute for an exam.

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