Tissue reactions to the separate implantation of individual constituent phases of dental amalgam, including assessment by energy dispersive X-ray microanalysis.

Soft tissue degradation of the 3 principal amalgam phases have been investigated in relation to their role in the formation of the amalgam tattoo. Each phase, finely powdered, was implanted subcutaneously into the submandibular region of guinea-pigs for periods ranging from 1 week to 1 year. The rates of breakdown were assessed radiographically and the final lesions were examined by light and electron microscopy and X-ray microanalysis. gamma 2 (Sn7Hg) phase degraded rapidly, mainly extracellularly, and did not produce a tattoo. Both mercury and tin disappeared from the lesion. gamma 1 (Ag2Hg3) phase degraded less rapidly, both extra and intracellularly, and produced a small tattoo. Mercury was lost from the lesion. gamma (Ag3Sn) phase degraded slowly, intracellularly, and produced a large tattoo. Tattoos always resulted from persistence of minute particles of silver and sulphur associated with basal lamina and connective tissue.