Effects of at-home and in-office bleaching and three composite types (hybrid, microhybrid, and nanofilled) on repair shear bond strength of aged composites: A preliminary study

Background: Only a few controversial studies have assessed the repair bond strength of fresh composite to aged composite. Moreover, no exist on composites bleached composites. Therefore, this preliminary study was conducted assess shear (SBS) three bonded nonbleached and at-home in-office composites.Materials Methods: In experimental in vitro study, 108 disks (36 specimens per composite) hybrid, microhybrid, nanofilled were divided into subgroups bleaching treatments: (control), bleaching, bleaching. Composite incubated for 4 weeks artificial saliva (also dipped tea coffee 3 h day). They then thermocycled (5000 cycles). Afterward, control group remained unbleached, while other groups according office home methods. repaired with same type. Their SBS mode failure measured analyzed using two-way ANOVA, Tukey, one-sample t-test, Chi-square tests (? = 0.05, ? 0.2).Results: The mean (standard deviation) values 20.71 ± 5.99, 21.06 6.68, 9.46 4.32 MPa, respectively. techniques “home (control)” were, respectively, 16.35 7.13, 16.39 8.07, 18.49 8.35 MPa. There significant difference among (two-way ANOVA P 0.000) but not nonbleaching/bleaching methods (P 0.176). interaction 0.017). between hybrid microhybrid significant. Nevertheless, had significantly poorer results compared both (Tukey 0.000). Both capable producing satisfactory clinical strengths (above 20 MPa) regardless or lack it. Nanofilled failed provide proper values, even (no-bleaching) group. By moving from Z100 Z250 Z350, modes shifted mostly cohesive adhesive < 0.05).Conclusion: Bleaching an might affect strength. Hybrid can clinically acceptable strengths, Nonetheless, is inferior them cannot appropriate (regardless bleaching).