Representative SEM micrographs for each experimental group in the cervical and apical area. Independent of the viscosity, ortho-phosphoric acid (OPA; capital letters) produced major silver deposits compared to meta-phosphoric acid (MPA; lower letters). Increased silver nitrate deposition was observed at the bottom of the hybrid layer (white hands) when OPA was applied. However, a small amount of discontinuous silver deposit can be seen in the MPA groups (red hands).

Representative SEM micrographs of dentin surfaces after conditioning with ortho-phosphoric acid (OPA; capital letters) and meta-phosphoric acid (MPA; lower letters) in the cervical and apical area. Acid etching with OPA totally removed the smear layer on the surface of the dentin tubules, and the tubular diameter was significantly enlarged (white hands) when compared to MPA, independent of the acid viscosity. Etching with MPA preserved the tubular diameter and the presence of the smear layer in the lumen of the tubule (red hands). When OPA was applied for different durations, some regions of the intertubular area with signs of erosion were observed with 15 seconds’ application (white asterisk) compared with 7 seconds’ application. In comparison, no significant difference was observed for MPA, despite the very superficial intertubular dentin etching pattern observed with 7 seconds’ application (red asterisks) compared to 15 seconds’ application. SEM images of the middle third are not presented in this figure because no significant difference in the conditioning pattern was observed when the cervical and medium thirds of the root canal were etched with OPA and MPA.