The summary The study of features of strength and microstructure of joints «enamel-filling» and «dentin-sealing» after the etching treatment agent containing Ag. Samples of tissues were fixed with adhesive composite material for mechanical testing in uniaxial compression. The study shows that the content of the etching agent, silver does not affect the bond strength of dentin with composite material. Metallographic investigation of the microstructure of the joints and the bordering regions of dentin showed the status of the border and its ability to suppress the growth of cracks. In the work by means of optical and scanning electron microscopes, microstructure of studied compounds affected dentine secondary caries in permanent teeth close to the border «dentin-sealing» after the etching treatment agent containing Ag. The presence in the etching agent nanocolloidal silver does not affect the adhesive strength of the boundary of the hard tissues of the tooth with a composite material and does not change the color of the hard tissues.