Coronal resistance to fracture of endodontically treated teeth submitted to light-activated bleaching

ObjectivesThe aim of this study was to assess the fracture resistance of endodontically treated teeth submitted to bleaching with 38% hydrogen peroxide activated by light-emitting diode (LED)-laser system.MethodsFifty maxillary incisors were endodontically treated, received a zinc phosphate barrier and were embedded in acrylic resin until cemento-enamel junction. The specimens were distributed into five groups (n = 10) according to the number of bleaching sessions: GI, no treatment (control); GII, one session; GIII, two sessions; GIV, three sessions and GV, four sessions. The whitening gel was applied to the buccal surface of the tooth and inside the pulp chamber for three times in each session, followed by LED-laser activation. Specimens were submitted to the fracture resistance test (kN) and data were submitted to the Tukey–Kramer multiple comparisons test.ResultsNo significant difference (p > 0.05) was found between GI (0.71 ± 0.30) and GII (0.65 ± 0.13), which presented the highest strength values to fracture. Groups III (0.35 ± 0.17), IV (0.23 ± 0.13) and V (0.38 ± 0.15) showed lower resistance to fracture (p < 0.01) when compared to GI and GII.ConclusionsThe fracture resistance of endodontically treated teeth decreased after two sessions of bleaching with 38% hydrogen peroxide activated by LED-laser system.