Effect of prolonged photo-irradiation time of three self-etch systems on the bonding to root canal dentine

To evaluate the effect of photo-irradiation time to the adhesive on the regional bond strength of a dual-cure resin core material to root canal dentine using photo and dual-cure adhesives with self-etching primer. Post spaces were prepared in extracted premolars and then the root canal dentine was treated with one of the following bonding procedures: (1) Clearfil SE Bond Primer/Bond (SE), (2) Nano-Bond Primer/Photo-cure adhesive (PNB), (3) Nano-Bond Primer/Dual-cure adhesive (DNB). Photo-irradiation was performed for 10 or 20 s from a coronal direction. The post spaces were then filled with a dual-cure composite resin (Build-It FR) and light-cured for 60 s. After 24 h storage, each specimen was serially sliced into 8, 0.6×0.6 mm-thick beams for the μTBS test. The bond strength data were divided into coronal and apical regions and analysed using three-way ANOVA and Games–Howell multiple comparison ( α=0.05). The μTBS of the photo-cure adhesive resin, SE and PNB, significantly decreased ( p