As a public health dentist and researcher, for years I saw the same pattern. Patients with deep root infections often had wider health problems, particularly those with diabetes. I did not yet understand why. Now, scientific studies are beginning to explain the link: treating a deep tooth infection may also help the body manage blood sugar.
A tooth infection might seem like a relatively minor health issue, but its effects can reach far beyond the mouth. Recent research found that people who had root canal treatment for long-lasting infections at the root tip experienced lower blood sugar and reduced inflammation over the following two years.
The same pattern was also seen in a longitudinal metabolomic analysis, which is a type of investigation that tracks people over time and uses detailed blood tests to measure hundreds of small molecules that show how the body is functioning. It allows scientists to see how a treatment influences overall metabolism, not just the infected tooth.
The patients in the metabolic analysis had apical periodontitis, which is a deep infection around the very tip of a tooth root. It often causes no pain, so many people do not know they have it until it shows up on an X-ray.
Blood tests before and after treatment showed improvements in long-term blood sugar and markers linked to heart and metabolic health. Simply removing the infected tissue inside the tooth seemed to benefit the body far from the site of the infection.
Koushik Chatterjee/Shutterstock
One reason is that these infections do not always stay local. When bacteria reach the tissues around the tooth root, the immune system responds. If the infection persists, the body produces low-grade inflammation: a constant, simmering immune response that never fully switches off.
This type of background inflammation can spread through the bloodstream. It can make it harder for the body to regulate sugar effectively because chronic inflammationinterferes with how insulin works, reducing the body’s ability to move sugar out of the blood and into cells.
To understand how this local problem can spark body-wide effects, researchers have pulled the evidence together: a narrative review summarises findings from many studies and maps the biological pathways that may link apical periodontitis to wider systemic disease.
Oral infections and diabetes
Many studies have explored this connection between oral infections and diabetes, and these findings can be summarised more simply. A review of seven studies found that people with diabetes are more likely to have persistent lesions around root-treated teeth.
In this case, it is diabetes that increases the risk of slow healing – not the other way around. High blood sugar weakens the immune response and disrupts bone repair, so lesions at the tip of the root (seen on X-rays as darker areas where bone has not healed properly) are more common.
Another review found that people with diabetes also face a higher risk of developing new apical periodontitis in root-filled teeth compared with people without diabetes. A clinical study involving hundreds of root-filled teeth reported the same trend.
Patients with diabetes had more persistent lesions than those without, reflecting poorer glycaemic control – meaning blood sugar levels remain consistently higher than recommended, something known to slow healing throughout the body, including in bone and connective tissue.
More information on this connection can be found in clinical guidelines from diabetes and oral-health organisations, and in research on wound healing and glycaemic control, which all highlight how high blood sugar impairs immune function and tissue repair.
Researchers are now studying what happens when these infections are treated successfully. One study using detailed metabolic testing found that root canal therapy not only resolved the infection but also led to better blood sugar control and reductions in inflammatory markers.
Root canal treatment removes the infected tissue and seals the space, stopping bacteria and toxins from affecting surrounding tissues. Another study confirmed that while lesions in root-treated teeth heal more slowly in people with diabetes, they do improve once the infection is managed. Even gradual healing seems to benefit the body as a whole.
These findings echo what we know about gum disease. Treating gum infections can improve blood sugar control in people with diabetes, a relationship supported by studies showing that periodontal therapy – professional treatment to remove plaque, tartar and infection from below the gumline – modestly reduces HbA1c levels.
HbA1c is a measure of average blood sugar over several weeks, so even a small reduction indicates improved long-term glucose control. Scientists suggest that reducing chronic inflammation in the mouth may help the body regulate sugar more effectively.
PeopleImages/Shutterstock
What makes infections at the tip of the tooth root so interesting is how easy they are to miss. Unlike gum disease, which often causes pain, swelling, or bleeding, apical infections can exist silently, while inflammation quietly spreads through the body. Reviews of apical periodontitis emphasise how often it goes unnoticed.
None of this means that root canals are a treatment for diabetes. The changes observed in studies are moderate and depend on factors such as infection severity and overall health.
And researchers are clear that causality is not yet established, so more controlled trials are needed. But the research strongly suggests that oral health has a wider role in metabolic health than most people realise.
For people with diabetes or at risk of it, this connection matters. A painful tooth, or even one that simply feels different, could be more than a local problem.
These findings also highlight a bigger issue, which is that dental care and medical care are often treated as separate worlds. The research on root canal infections shows how closely linked they can be. A properly treated tooth can save more than a smile; it may contribute to better overall health.
