Adhesive cementation of zirconia posts to root dentin: evaluation of the mechanical cycling effect

this study evaluated the effect of mechanical cycling on the bond strength of zirconia posts to root dentin. thirty single-rooted human teeth were transversally sectioned to a length of 16 mm. the canal preparation was performed with zirconia post system drills (cosmopost, ivoclar) to a depth of 12 mm. for post cementation, the canals were treated with total-etch, 3-steps all-bond 2 (bisco), and the posts were cemented with duolink dual resin cement (bisco). three groups were formed (n = 10): g1 - control, no mechanical cycling; g2 - 20,000 mechanical cycles; g3 - 2,000,000 mechanical cycles. a 1.6-mm-thick punch induced loads of 50 n, at a 45° angle to the long axis of the specimens and at a frequency of 8 hz directly on the posts. to evaluate the bond strengths, the specimens were sectioned perpendicular to the long axis of the teeth, generating 2-mm-thick slices, approximately (5 sections per teeth), which were subjected to the push-out test in a universal testing machine at a 1 mm/min crosshead speed. the push-out bond strength was affected by the mechanical cycling (1-way anova, p = .0001). the results of the control group (7.7 ± 1.3 mpa) were statistically higher than those of g2 (3.9 ± 2.2 mpa) and g3 (3.3 ± 2.3 mpa). it was concluded that the mechanical cycling damaged the bond strength of zirconia posts to root dentin.