Effect of Curing Modes of Dual-curing Core Systems on Microtensile Bond Strength to Dentin and Formation of an Acid-Base Resistant Zone

Purpose: To evaluate the microtensile bond strength (µTBS) and acid-base resistant zone (ABRZ) of two dualcuring core systems to dentin using four curing modes. Materials and Methods: Sixty-four caries-free human molars were randomly divided into two groups according to two dual-curing resin core systems: (1) Clearfil DC Core Automix; (2) Estelite Core Quick. For each core system, four different curing modes were applied to the adhesive and core resin: (1) dual-cured and dual-cured (DD); (2) chemically cured and dual-cured (CD); (3) dual-cured and chemically cured (DC); (4) chemically cured and chemically cured (CC). The specimens were sectioned into sticks (n = 20 for each group) for the microtensile bond test. µTBS data were analyzed using two-way ANOVA and the Dunnett T3 test. Failure patterns were examined with scanning electron microscopy (SEM) to determine the proportion of each mode. Dentin sandwiches were produced and subjected to an acid-base challenge. After argon-ion etching, the ultrastructure of ABRZ was observed using SEM. Results: For Clearfil DC Core Automix, the µTBS values in MPa were as follows: DD: 29.1 ± 5.4, CD: 21.6 ± 5.6, DC: 17.9 ± 2.8, CC: 11.5 ± 3.2. For Estelite Core Quick, they were: DD: 48.9 ±5.7, CD: 20.5 ± 4.7, DC: 41.4 ± 8.3, CC: 19.1 ± 6.0. The bond strength was affected by both material and curing mode, and the interaction of the two factors was significant (p 0.001). Within both systems, there were significant differences among groups, and the DD group showed the highest µTBS (p 0.05). ABRZ morphology was not affected by curing mode, but it was highly adhesive-material dependent. Conclusion: The curing mode of dual-curing core systems affects bond strength to dentin, but has no significant effect on the formation of ABRZ. Keywords: curing modes, dual-curing core system, microtensile bond strength, acid-base resistant zone, dentin