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Oncology/Hematology

Published: Sep 13, 2013

Action Points

Individuals with cavities in their teeth had a reduced incidence of head and neck cancer, perhaps because of heightened immune activity, researchers said.

Among 399 patients with head and neck cancer, current or previous dental caries were significantly less common than in 221 individuals without a cancer diagnosis, according to a single-center, case-control study at the State University of New York at Buffalo led by Mine Tezal, DDS, PhD.

"To our knowledge, the present study suggests, for the first time, an independent association between dental caries and head and neck squamous cell carcinoma," Tezal and colleagues wrote online in JAMA Otolaryngology-Head & Neck Surgery.

They also proposed a mechanism for the apparent protective effect: that cariogenic, lactic acid-producing bacteria prompt cell-mediated Th1 immune responses that suppress tumor formation.

Tezal and colleagues noted that the inverse relationship between dental caries and head and neck cancer stands in contrast to previous work examining periodontitis, which found that infections below the gum line are associated with increased cancer risk.

"Although these two oral diseases are often combined in a single category as indicators of poor oral health, they are distinct in terms of both etiology and outcome," the researchers wrote.

The bacteria responsible for these conditions are different, Tezal and colleagues indicated, 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," they asserted.

For the current study, Tezal and colleagues examined records of patients older than 21 seen in the university's dental and maxillofacial prosthetics department from 1999 to 2007, identifying 399 who were newly diagnosed with head and neck squamous cell carcinoma. They also reviewed records of 221 other patients seen in the department during the same period. Patients with a history of cancer, dysplasia, or immunodeficiency were excluded from both groups. Controls included general dental patients as well those diagnosed with such conditions as oral warts, traumatic injuries, cysts, and abscesses.

The following variables were evaluated: caries at examination, the presence of crowns or fillings, number of teeth with endodontic treatments, missing teeth, and alveolar bone loss (as a measure of periodontitis). Teval and colleagues also calculated a composite measure of decayed, missing, and filled teeth (DMFT). These measurements were made by a blinded examiner from panoramic radiographs included in the patients' records.

Means for these indicators among cases versus controls were as follows:

• Number of teeth with caries: cases 1.58 (SD 2.52), controls 2.04 (SD 2.15, P=0.03)
• Number of crowns: cases 1.27 (SD 2.65), controls 2.10 (SD 3.57, P=0.004)
• Number of endodontic treatments: cases 0.56 (SD 1.24), controls 1.01 (SD 2.04)
• DMFT: cases 16.40 (SD 6.79), controls 15.39 (SD 6.31, P=0.09)
• Alveolar bone loss: cases 4.03 mm (SD 1.33), controls 2.44 mm (SD 0.93, P<0.001)

Teval and colleagues found that the associations between caries counts and cancer were restricted to tumors of the oral cavity and oropharynx (both P<0.001 for trend); in cases involving laryngeal cancers, there was no difference in caries counts between cases and controls (P=0.67).

The researchers acknowledged that some of the variables they assessed had somewhat murky connections to caries versus other conditions, such as periodontitis or trauma. For example, they had no data on the causes of missing teeth. And, because the DMFT index includes missing teeth as a component, "it does not represent dental caries history accurately," Teval and colleagues wrote.

Other limitations included lack of data on potential confounders such as patients' diet and socioeconomic status and on details of dental caries such as depth and location.

Assuming that the association between caries and reduced cancer risk is real, however, Teval and colleagues suggested that one could regard the cariogenic bacteria as beneficial overall, with caries "a form of collateral damage." Therefore an appropriate strategy could be to target that effect specifically without aggressively targeting the bacteria.

"Antimicrobial treatment, vaccination, or gene therapy against cariogenic bacteria may lead to more harm than good in the long run," they warned.

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