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Figure 2. High-magnification TEM micrographs showing the changes that occurred around the isolated silver grains (arrows) in the filled adhesive layer (FA) after aging in artificial saliva. (A) 24 hrs, (B) 1 mo, (C) 3 mos, (D) 6 mos, and (E) 12 mos. Isolated silver grains increased in size and density, and some were eventually surrounded by a secondary rosette of silver grains (C, D). The precursors of water-filled channels (i.e., water trees) that could be seen at 6 mos were attributed to the increase in density of these rosettes of silver grains. Frank water trees were evident at 12 mos (E). A siliceous hydrogel layer (arrowheads) could also be observed along the periphery of the fluoroaluminosilicate glass fillers (G) beginning at 3 mos.
