Should acid etching be performed prior to nonvital bleaching?

This study sought to measure the microtensile bond strength of a nanofilled composite resin to human dentin after phosphoric acid etching followed by nonvital bleaching. Scanning electron microscopy was used to analyze fracture modes. Twenty extracted sound human maxillary premolars were prepared for Class I defects and assigned randomly to 4 groups (n = 5): Group 1 (control group) samples were unbleached and had no previous acid etching; Group 2 samples were bleached only, Group 3 samples were acid-etched for 15 seconds prior to bleaching, and Group 4 samples were acid-etched for 30 seconds prior to bleaching. There were no statistically significant differences of bond strength values among Groups 1-3; however, the mean values of Group 4 were statistically lower compared with the other groups.