Methods: Specimens of three desensitizers (All-bond2, Systemp,control)etched or not were studied with FE-SEM to identify the amount and distribution of silver uptake, then subjected to image analysis by NIH Image PC. Nanoleakage scores of each specimen were calculated as the percentage width of the specimen that was penetrated by silver nitrate.
Results: the nanoleakage scores of applying All-bond2 or Systemp desensitizers had significant less then no desensitizers (control) in the pre-etched group/post-etched group, but had no significant difference in non-etched group. The nanoleakage scores has no significant difference between All-bond2 and Systemp in all groups (P>0.05).When no desensitizers apply, the nanoleakage scores in pre-etched group or post-group had significant difference with non-etched group (P<0.05),but no significant difference between pre-etched group and post-group. The backscattered and secondary electron SEM images show the silver deposited at the base of the hybrid layer, some penetrated around the dentinal tubule, most nanoleakage were reticular type and the spot type also appeared occasionally.
Conclusions:The application of All-bond2 desensitizing agent or Systemp desensitizing agent can reduced the nanoleakage of dentin interface,Single etching the smear layers without apply desensitizing agent would increase the nanoleakage of dentin interface.