Abstract
The occurence of blue - gray areas in the soft tissue represent one of the problems affectin patients whose teeth have been restored using metalic materials.It is caused by mechanical penetration of a metalic material into sof tissue.The aim of the study was to determine an alternative mechnism of the origin of pigmentations,based on the corrosion interactions of metalic materials used in prosthodontics. with the oral enviroment.The formation of soluble silver compounds in the sulcular area or in a crevice between the crowns facilitates their transport to the soft tissue and subsequent deposition