Diatoms can be found in foreign body-type granulomas of the oral cavity.

Phyllum: Bacillariophyta

Description: aquatic microscopic single-celled microalgae

Energy source: photosynthesis


The cell wall is rich in silica.

Habitat: fresh or salt water


Sources of human exposure may include:

(1) ingestion of food or water containing diatoms

(2) aspiration of water containing diatoms

(3) inhalation of diatoms in the air

(4) oral trauma in the presence of diatoms

(5) exposure to dental alginate (used for making dental impression)


Implantation of diatoms into the submucosa or soft tissue elicits a foreign body granulomatous reaction. This tends to happen in the region of the mandible.


The size of diatoms typically range from 5 to 200 microns, but can measure up to 500 microns in diameter.



(1) exclusion of other causes

(2) recognition of cell features (if large enough)

(3) electron microscopy (especially with a probe to demonstrate silica)

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