Figure 4. TEM micrographs from (A-B) Group 5-4-1 (40 vol% water), and (C-D) Group 3-6-1 (60 vol% water). C, composite; A, filled adhesive; D, dentin. Open arrowhead: F-PRG fillers. (A) Stained, demineralized section from Group 5-4-1. There was an increased aggressiveness of the self-etching primer with increasing water concentration, with the formation of a 1.5- to 2-µm-thick hybrid layer (between open arrows). (B) The corresponding unstained undemineralized section revealed a 1.5- to 2-µm-thick partially demineralized zone (between open arrows) in which reticular patterns of nanoleakage could occasionally be seen. There were no silver deposits within the interfibrillar spaces of the underlying dentin. (C) Stained, demineralized TEM from Group 3-6-1, showing a similarly thick hybrid layer (between open arrows), but with further extensions to form peritubular cuffs (pointers) around the dentinal tubules. (D) The corresponding unstained, undemineralized TEM. The low resin concentration and the increased water content resulted in the extensive deposition of silver within the partially demineralized zone (between open arrows).