You probably know the dull ache of a tooth that never quite feels right.
Most of us put it off and hope it settles on its own. Some skip the dentist for years at a time.
A new study from King's College London suggests that leaving an infected tooth root alone may do more than threaten the tooth itself.
It may also quietly push up risk markers for heart disease and type 2 diabetes.
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The condition is called apical periodontitis, an infection at the very tip of a tooth's root.
According to King's College London, its global prevalence is around 52%, meaning more than half of the world's population has at least one affected tooth, and it is regarded as the third most prevalent oral disease globally.
What a root canal did to patients' blood
The study, published in November 2025 in the Journal of Translational Medicine, followed 65 patients from Guy's and St Thomas' NHS Foundation Trust for two years after a successful root canal.
The researchers drew blood samples at five points over that time.
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They used a lab method called nuclear magnetic resonance spectroscopy, which reads chemical signals from small molecules in the blood.
Blood sugar fell significantly by the two-year mark. Cholesterol and fatty acids dropped in the first few months after treatment.
Tryptophan, an amino acid tied to mood and inflammation, rose steadily.
More than half of the molecules the team measured shifted in ways the authors describe as pointing to better metabolism and less inflammation across the body.
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Why a bad tooth can reach the heart
Dentists have long known that gum disease and heart disease travel together.
The new work points to the inside of the tooth, not just the gum line.
When the soft pulp inside a tooth dies and the root tip gets infected, bacteria can leak into the bloodstream.
That triggers low-grade inflammation, which over time may lift blood sugar and cholesterol.
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These are the same markers that define metabolic syndrome, the cluster of conditions that raises the odds of heart attack, stroke and type 2 diabetes.
What this means for patients with a nagging tooth
Lead author Dr Sadia Niazi, a senior clinical lecturer in endodontology at King's College London, says the results suggest that root canal treatment does more than save a tooth.
She has called for closer coordination between dentists and primary care doctors, so that patients with persistent root tip infections also have their blood sugar and cholesterol monitored.
Many of these infections cause little pain early on. People can carry a quiet one in the jaw for years before a dental checkup turns it up.
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This article is made and published by Mie Hermansen, who may have used AI in the preparation.