MedicalResearch.com: What are the main findings of the study?
Dr. Tezal: We observed an inverse association between dental caries and head and neck cancer (HNSCC), which persisted among never smokers and never drinkers. Besides untreated caries, two other objective measures of long-standing caries history (endodontic treatments and crowns) were also inversely associated with HNSCC with similar effect sizes, supporting the validity of the association. Missing teeth was associated with increased risk of HNSCC in univariate analyses, but after adjustment for potential confounders, its effect was attenuated and was no longer statistically significant.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Tezal: Yes, an inverse association between dental caries and HNSCC was an unexpected finding since dental caries has been considered a sign of poor oral health along with periodontal disease. Periodontal disease, a chronic inflammatory disease, was associated with an increased risk of HNSCC, which explains the lack of association with missing teeth since more than half of the teeth are lost due to periodontal disease.
MedicalResearch.com: What should clinicians and patients take away from your report?
Dr. Tezal: The message, of course, is not to get caries to prevent cancer.
Dental caries is the demineralization of tooth structures by lactic acid from fermentation of carbohydrates by commensal bacteria, including streptococci, lactobacilli, actinomyces, and bifidobacteria, the same kinds of bacteria used in yogurt production. These commensal bacteria have important roles in local mucosal and systemic immunity, and their reduction has been associated with chronic inflammatory diseases, allergies and cancer. They produce antitumorigenic and antimutagenic compounds, favor an anti-inflammatory response, and inhibit adhesion and growth of pathogenic bacteria.
It is important to understand that cariogenic bacteria are part of the normal flora, and their presence is not sufficient to cause dental caries in the absence of the other risk factors, such as dental plaque, frequent consumption of sugars, and reduced saliva. In addition, caries is a dental plaque-related disease. Lactic acid bacteria cause demineralization (caries) only when they are in dental plaque at immediate contact with the tooth surface. The presence of these otherwise beneficial bacteria in saliva or on mucosal surfaces may protect the host against chronic inflammatory diseases and HNSCC. We could think of dental caries as a collateral damage, and develop strategies to reduce its risk while preserving the beneficial effects of the lactic acid bacteria. For example, antimicrobial treatment, vaccination or gene therapy against cariogenic bacteria may lead to more harm than benefit in the long run, including a shift in microbial ecology towards pathogenic bacteria, and increased risks of chronic inflammatory diseases and cancer. Instead, strategies preserving microbial ecology beneficial to the host such as mechanical plaque control (brushing and flossing), preservation of saliva, fluoride use, and refraining from frequent intake of sugars, antimicrobials, and smoking may be wiser.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Tezal: This study provides insights for prospective studies to assess potential beneficial effects of lactic acid bacteria and the associated immune responses on HNSCC.
Tezal M, Scannapieco FA, Wactawski-Wende J, et al. Dental Caries and Head and Neck Cancers. JAMA Otolaryngol Head Neck Surg. 2013;():-. doi:10.1001/jamaoto.2013.4569.