Mechanical properties of the dentin matrix submitted to hydrogen peroxide agents containing TiO2 associated with violet LED

Purpose The objective of this study was to investigate the effect of dentin matrix submitted to bleaching treatments with hydrogen peroxide (HP) agents incorporated with 1% titanium dioxide (TiO 2 ) nanotubes, with or without the application of violet LED. Methods Demineralized dentin beams were assigned to groups (n=10): (saliva; 35%PH/ Whiteness HP, FGM; 7.5%HP/ White Class, FGM; 35%HP + TiO 2 ; 7.5%HP + TiO 2 ) associated or not with LED. Bleaching treatments were performed for 30 minutes each session in 3 clinical sessions. LED (Bright Max Whitening, MMOptic) was applied in 20 cycles of 60 s of light with a 30 s rest interval each session. Dentin matrix stability by apparent modulus of elasticity (ME) after each bleaching session, dentin matrix mass loss (ML) before and after bleaching treatments and ultimate tensile strength (TS) after treatments were evaluated. Results The generalized linear models for repeated measures in time showed no significant differences among the treatments regarding ME (p=0.6878). In the presence of LED, Kruskal-Wallis showed significant mass loss for the groups treated with 35%HP and 35%HP + TiO 2 than the same treatments without LED (p=0.0002). In the absence of LED, 5%HP and HP35% showed more significant mass loss than groups 7.5%HP and 7.5%HP + TiO 2 (p<0.0001). Conclusion Bleaching agents did not impact the dentin matrix ME, but the association of LED with 35%HP may decrease dentin mass and TS. However, TiO 2 provided higher TS to dentin matrix when incorporated into a 35% HP agent.