This study evaluated comparatively by scanning electron microscopy (SEM) the effect of different dental conditioners on dentin micromorphology, when used according to the same protocol. Forty dentin sticks were obtained from 20 caries-free third human molars and were assigned to 4 groups corresponding to 3 conditioners (
phosphoric acid 37%,
Clearfil SE Bond and
iBond) and an untreated control group. After application of the conditioners, the specimens were immersed in 50%
ethanol solution during 10 s, chemically fixed and dehydrated to prepare them to SEM analysis. In the control group, dentin surface was completely covered by
smear layer and all dentinal tubules were occluded. In the
phosphoric acid-etched group, dentin surface was completely clean and presented exposed dentinal tubule openings; this was the only group in which the tubules exhibited the funnel-shaped aspect. In the groups conditioned with
Clearfil SE Bond primer and
iBond, which are less acidic than
phosphoric acid, tubule openings were occluded or partially occluded, though
smear layer removal was observed. SE Bond was more efficient in removing the
smear layer than
iBond. In the
Clearfil SE Bond group, the cuff-like aspect of peritubular dentin was more evident. It may be concluded all tested conditioners were able to change dentin morphology. However, it cannot be stated that the agent aggressiveness was the only cause of the micromorphological alterations because a single morphological pattern was not established for each group, but rather an association of different aspects, according to the aggressiveness of the tested conditioner.