Commentary: Is tooth loss good or bad for general health?

Abstract

Abnet et al. 1 show that tooth loss is associated with increased risk of mortality from upper gastrointestinal cancer, heart diseases, and stroke. In the last decade, those working in oral health research, especially within periodontology, have shown increasing interest in studying the possible link between oral health and systemic health outcomes. The study by Abnet et al. evidently shows the difficulties and limitations in study design faced by proponents of a causal relationship. It is simple to think of a randomized controlled trial to test the hypothesis of a relationship between oral health status and systemic health outcomes (not surrogate endpoints such as inflammatory cytokine levels): patients with advanced periodontal disease are randomly allocated to two groups in which one receives standard treatment and maintenance care and the other receives no treatment. However, this study design would be considered unethical. Furthermore, differences in treatment outcomes between the two groups, such as episodes of stroke, will take many years to manifest, and it can be assumed that the treatment reduces/reverses the risk generated by periodontal diseases. Consequently, the only practical alternative research data must come from large-scale cohort studies, such as that reported by Abnet et al., or from case‐control studies. A persistent problem, however, is the assessment of oral health. Although the pathological mechanism in the connection between oral infection and systemic health is not yet known, it is widely thought that the chronic infection due to periodontal diseases is more likely to cause systemic hazard because periodontal infection is chronic and periodontal pathogens enter the systemic blood circulation. However, diagnosis of periodontal diseases is not straightforward and clinical examination to establish diagnosis is time-consuming. Simple indices to screen and summarize periodontal diseases have been used in epidemiological research, but it is questionable that these indices can reliably represent the underlining disease status. An alternative is to use the number of lost teeth, which seems to be a reliable measure of oral health status. Although we accept that tooth loss is less prone to measurement error, the interpretation of tooth loss remains debatable. For the rural Chinese population, Abnet et al. argue that periodontal disease, not dental caries, is the main cause of tooth loss, and this supposition affects only the biological mechanisms they propose and not the accuracy of the risk estimates they report. This supposition might be true, though there is more than one interpretation of their risk estimates.