There is no credible evidence that having root canal treatment causes any type of cancer. Most of the websites claiming that root canal treatment is the cause of cancer (or cancer recurrence) refer to a study done nearly 100 years ago that has been debunked and contradicted by more recent research. In a root canal procedure, dentists remove the diseased or injured pulp from a tooth. Claims that root canal treatment causes cancer and other diseases are based on the notion that bacteria and viruses are left behind or ‘hide’ in the tip of the root canal and spread to other parts of the body. But the purpose of root canal treatment is to eliminate bacteria in the affected tooth and seal off the cavity to prevent re-infection and save the tooth. Scientific evidence suggests you have a greater risk of illness from an untreated infected root canal or having a tooth removed than from successfully completed root canal therapy. There is a much higher risk of bacteremia (bacteria entering the bloodstream) with a tooth extraction. Our mouths are home to more than 700 bacterial species, many of which can cause periodontal (gum) disease or tooth loss. There is increasing evidence that these diseases increase the risk of oral and gastrointestinal cancers, particularly in people who smoke and drink alcohol. Research into the association between oral health and cancer is ongoing, and so far there is no link between endodontic (root canal) disease and cancer.