Effect of high-concentrated bleaching agents on the bond strength at dentin/resin interface and flexural strength of dentin

this study evaluated the effect of bleaching agents on bond strength at the dentin/resin interface and the flexural strength of dentin. forty maxillary canines were selected for the study. in the shear strength test, 40 slabs of intracoronary dentin (5 x 5 mm) obtained from buccal surfaces of the crowns were included in acrylic resin. in the flexural strength test, 40 dentin bars (8 x 2 x 2 mm) were obtained from the roots. the 40 hemi-sections of the lingual surface were prepared for scanning electron microscopy (sem). the specimens were divided into 4 groups according to the bleaching protocol (n=10): unbleached (control), sodium perborate + 20% hydrogen peroxide (sp + 20% hp), 37% carbamide peroxide (37% cp) and 38% hydrogen peroxide (38% hp). after 7 days, the bond strength specimens were restored and tested. dentin bars were bleached and subjected to a three-point bending test. data (mpa) were analyzed by anova and tukey's test (α=0.05). in the shear test, the control group was superior (p<0.05) to the bleached groups, which, in turn, were statistically similar (p>0.05). in the flexural strength test, the control group also had the highest values and differed significantly from the other groups (p<0.05). sem revealed smear layer in all groups, with fissures in the bleached specimens. sp + 20% hp and 38% hp showed discontinuous interfaces with few tags. in conclusion, bond strength of restorative material to dentin and flexural strength of dentin were reduced after the use of high-concentration bleaching agents.