Periodontitis is a public health issue, being one of the most prevalent diseases worldwide. However, the aetiology of the disease is still unclear: genetics of patients cannot explain the dispersed or isolated localisation of gingival pockets, while bacteria-based models are insufficient to distinguish gingivitis and periodontitis. The possible role of parasites in the establishment of periodontitis has been poorly studied until now. The aim of this project was to study a potential link between colonisation of gingival crevices by the amoeba Entamoeba gingivalis and periodontitis. In eight different dental clinics in France, samples were taken in periodontal pockets (72) or healthy sites (33), and submitted to microscopic observation and molecular identification by PCR with a new set of primers designed to specifically detect E. gingivalis. This blind sample analysis showed the strong sensitivity of PCR compared with clinical diagnosis (58/72 = 81%), and microscopy (51/65 = 78%). The results of this work show that the parasites detected by microscopy mainly – if not exclusively – belong to the species E. gingivalis and that the presence of the parasite is correlated with periodontitis.

The protozoan Entamoeba gingivalis resides in the oral cavity and is frequently observed in the periodontal pockets of humans and pets. This species of Entamoeba is closely related to the human pathogen Entamoeba histolytica, the agent of amoebiasis. Although E. gingivalis is highly enriched in people with periodontitis (a disease in which inflammation and bone loss correlate with changes in the microbial flora), the potential role of this protozoan in oral infectious diseases is not known. Periodontitis affects half the adult population in the world, eventually leads to edentulism, and has been linked to other pathologies, like diabetes and cardiovascular diseases. As aging is a risk factor for the disorder, it is considered an inevitable physiological process, even though it can be prevented and cured. However, the impact of periodontitis on the patient's health and quality of life, as well as its economic burden, are underestimated. Commonly accepted models explain the progression from health to gingivitis and then periodontitis by a gradual change in the identity and proportion of bacterial microorganisms in the gingival crevices. Though not pathognomonic, inflammation is always present in periodontitis. The recruitment of leukocytes to inflamed gums and their passage to the periodontal pocket lumen are speculated to fuel both tissue destruction and the development of the flora. The individual contribution to the disease of each bacterial species is difficult to establish and the eventual role of protozoa in the fate of this disease has been ignored. Following recent scientific findings, we discuss the relevance of these data and propose that the status of E. gingivalis be reconsidered as a potential pathogen contributing to periodontitis.

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Direct microscopy appears as the method of choice for confirming clinical diagnosis and could become a routine chair-side technique.

The pathogenicity of Trichomonas species is well documented. Although their exact involvement in gum disease is not fully understood, recent studies suggest a correlation between these protozoa and periodontitis. This case report details the first chair-side observation in Europe of an oral trichomonad infection in a child with periodontitis, by direct microscopy. The dramatic recovery of the patient, observed following administration of an anti-parasitic treatment, confirms the necessity of further investigation in this field.