Einfluss verschiedener Bleaching-Einlagen auf den Haftverbund von zwei unterschiedlichen Befestigungskompositen zum Wuzelkanaldentin

Background and Aims Intrinsically discolored teeth can be whitened by bleaching agents, which are injected inside the pulp. The requirements for a long-term succeeding therapy are an adequate root canal filling with a subsequent coronal seal of the access cavity with composite. The adhesion of the composite to dentine is very crucial. This in-vitro study aimed to investigate the effect of internal bleaching with two bleaching materials sodium perborate and Perfect Bleach Office+ in the bond strength of two luting composites, the self-adhesive BiFix SE and the multi-step luting composite Rebilda DC. Materials and Methods This study contained 70 human, straight-rooted teeth with a single root canal and a round cross section. The decoronation of the root canal was followed by the mechanical preparation. As soon as an exact length of 8 mm was achieved for all the teeth, the preparation is completed. 48 of the 70 teeth were assigned to either of the testing bleach materials. Thereof, 24 teeth were prepared with sodium perborate and 24 with Perfect Bleach Office+. The control group of 22 teeth was not exposed to any whitening treatment. After 7 days of bleaching, each tooth was rinsed in an identical manner. The adjusted and conditioned steel spreader was inserted into the root canal of each tooth using both composites. Therefore, the three groups were each divided equally amongst the composite BiFix SE and Rebilda DC. After 7 days of hardening, the pull-out test was performed in the Zwick universal testing device. The physical effort applied by the machine to extrude the spreader out of the root canal was documented. Results The highest bond strength was achieved by Perfect Bleach Office+ with Rebilda DC as the composite (8,17 MPa). Similar results were reached by the group with sodium perborate and Rebilda DC (6,72 MPa) and the control group with Rebilda DC (7,63 MPa), as well as the control group with BiFix SE (7,82 MPa). Only sodium perborate and Perfect Bleach Office+ along with BiFix SE showed significantly lower adhesion coefficients compared to all the other groups. Conclusion The varying adhesion coefficients resulted from different combinations of composites and bleaching agents. The usage of Rebilda DC and BiFix SE showed similar bonding rates when used without bleaching agents. If an internal bleaching therapy is utilized, the usage of Rebilda DC is recommended over BiFix SE because the adhesion coefficient was constant independent of the bleaching agents, sodium perborate and Perfect Bleach Office+.