The Effect of Intermediate Layer Materials on the Bond Strength to Hydraulic Calcium-Silicate-Based Cements Used in Vital Pulp Therapy: An In Vitro Study

Objective: This in vitro study evaluated the shear bond strength (SBS) between 4 hydraulic calcium silicate-based cements (HCSCs) and 3 intermediate layer materials used in vital pulp therapy (VPT). Methods: Two hundred forty specimens were divided into 12 groups and prepared using combinations of HCSCs (mineral trioxide aggregate [MTA], Biodentine, NeoPutty, MTA vital pulp therapy [MTAvpt]) and 3 intermediate layer materials (self-adhesive flowable composite [SAFC], resin-modified glass ionomer [RMGI], and flowable composite [FC]). SBS was measured using a universal testing machine, and failure modes were evaluated under stereomicroscopy. Data were analyzed using two-way ANOVA and Tukey's test with an α = 0.05. Results: SBS was affected by HCSC (P < .001), intermediate layer material (P < .001), and their interaction (P = .016). Biodentine exhibited the highest mean SBS (17.24 ± 12.09 MPa), followed by MTAvpt (12.59 ± 10.22 MPa), MTA (11.04 ± 9.80 MPa), and NeoPutty (9.84 ± 10.60 MPa). For intermediate layer materials, SAFC demonstrated the highest mean SBS (21.17 ± 10.88 MPa), significantly greater than FC (13.41 ± 9.07 MPa), and RMGI (3.45 ± 2.52 MPa). The combination Biodentine-SAFC yielded the highest mean SBS value, while groups with RMGI showed the lowest SBS values, with predominantly adhesive failures. Conclusion: Under the conditions of this in vitro study, bond strength between HCSCs and intermediate materials varied according to both material types. SAFC and, in some cases, FC exhibited higher initial adhesion to the tested HCSCs, while RMGI showed consistently low SBS.