Fracture resistance of teeth submitted to several internal bleaching protocols.

Materials and methods: After endodontic treatment, fifty bovine extracted teeth were divided into five groups (n = 10): G1—unbleached; G2—35HP; G3—37CP; G4—15HPTiO2 photoactivated by LED-laser and G5—SP. In the G2 and G4, the bleaching protocol was applied in 4 sessions, with 7 days intervals between each session. In the G3 and G5, the materials were kept in the pulp teeth for 21 days, but replaced every 7 days. After 21 days, the teeth were subjected to compressive load at a cross head speed of 0.5 mm/min, applied at 135° to the long axis of the root using an eletromechanical testing machine, until teeth fracture. The data were submitted to ANOVA and Tukey tests (α = 5%).