Dental Caries Could Offer Protection Against Cancer

A new study suggests that people with cavities in their teeth have a reduced incidence of head and neck cancer, perhaps due to heightened immune activity.

Researchers at the State University of New York (SUNY; Buffalo, USA) examined the records of all patients older than 21 at the SUNY dental and maxillofacial prosthetics department from 1999 to 2007, identifying 399 who were newly diagnosed with head and neck squamous cell carcinoma (HNSCC). They also reviewed the records of 221 other patients seen in the department during the same period. Controls included general dental patients as well those diagnosed with such conditions as oral warts, traumatic injuries, cysts, and abscesses. Patients with a history of cancer, dysplasia, or immunodeficiency were excluded from both groups.

The results showed that after adjustment for age at diagnosis, sex, marital status, smoking status, and alcohol use, those in the upper tertiles of caries, crowns, and endodontic treatments were less likely to have HNSCC than those in the lower tertiles. The researchers then proposed a mechanism for the apparent protective effect: that cariogenic, lactic acid-producing bacteria prompt cell-mediated Th1 immune responses that suppress tumor formation. The study was published online on September 12, 2013, in Otolaryngology Head and Neck Surgery.

“To our knowledge, the present study suggests, for the first time, an independent association between dental caries and head and neck squamous cell carcinoma,” concluded lead author Mine Tezal, DDS, PhD, and colleagues. “Assuming that the association between caries and reduced cancer risk is real, one could regard the cariogenic bacteria as beneficial overall, with caries ‘a form of collateral damage’.”

The researchers acknowledged that the study contrasts previous work examining periodontitis, which found that infections below the gum line are associated with increased cancer risk. They indicated, however, that the bacteria responsible for these conditions are different, and provoke different types of immune responses. In the case of periodontitis, these responses are dominated by Th2/Th17-type attacks, which have been generally associated with increased risk of cancer. Th1 responses, on the other hand, have consistently been associated with decreased risk of cancer.

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