Identification of a foreign body using energy dispersive x-ray analysis

A foreign object, presumably swallowed during a dental appointment, was recovered by using an esophagoscope and thought to be a piece of dental impression material, probably alginate. It was identified as being of nondental origin by means of visible light and scanning electron microscopy (SEM), the latter coupled to an energy dispersive X-ray analyzer. Histologic examination revealed some amorphous crystalline material surrounded by parakeratin and exfoliated squamous cells. The material was essentially radiolucent. A known dental alginate impression material contained diatomaceous earth filler (siliceous shells of diatoms), but no microscopic symmetrical figures were seen in the foreign body. After dehydration, both materials were carbon-coated and observed in an SEM at 20 kV at magnifications up to 2000 X. The spectrum of secondary X-rays produced by the scanning electron beam revealed only magnesium in the foreign body and mostly silicon in the dental alginate. There are no known dental products that contain magnesium as the only inorganic ingredient and so the foreign body is believed to be not of dental origin. The patient may have had an antacid or laxative having magnesium as a major ingredient in the stomach, and this may have been refluxed from the stomach after stimulation of the normal gag reflex during the dental procedure.