Comparative Evaluation of Shear Bond Strength Between Monolithic Zirconia and Three Different Core Build-Up Materials

This in vitro study aimed to evaluate and compare the shear bond strength (SBS) between monolithic zirconia (MZ) and different core build-up materials. Sixty cylindrical MZ specimens were fabricated and divided into three groups (<i>n</i> = 20) based on the type of core build-up material: nanohybrid composite resin (NHCR), glass ionomer cement (GIC), and zirconia-reinforced glass ionomer cement (zirconomer). All specimens were subjected to airborne-particle abrasion with aluminum oxide and bonded using a self-adhesive dual-cure resin cement. After 24 h of storage in distilled water at 37 °C, SBS testing was performed using a universal testing machine. Failure modes were examined under a stereomicroscope and classified as adhesive, cohesive, or mixed. The NHCR group exhibited the highest SBS values (48.32 ± 12.49 MPa), followed by the Zirkonomer group (14.19 ± 3.66 MPa), and the GIC group (10.37 ± 4.21 MPa). The SBS of NHCR was significantly higher than that of both Zirconomer and GIC (<i>p</i> < 0.001). Although no significant difference was found between Zirconomer and GIC, Zirconomer demonstrated higher mean bond strength. Within the limitations of this study, NHCR showed the highest bond strength to monolithic zirconia. Zirconomer performed better than conventional GIC; however, further investigations involving different surface treatments and long-term clinical conditions are recommended to enhance its bonding efficacy.