Surface treatment of Y-TZP with glass beads: Effects on flexural strength and bonding to resin cement

ABSTRACT Statement of problem Achieving durable bonding between yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and resin cements remains a clinical challenge, as conventional surface treatments may introduce defects and compromise material stability, warranting alternative methods such as glass-bead abrasion. Purpose The purpose of this in vitro study was to evaluate the effects of different surface treatments on the biaxial flexural strength, Weibull reliability, resin cement bond strength, and crystalline phase stability of Y-TZP before and after artificial aging. Material and methods Thirty disk‑ and 10 cube‑shaped Y‑TZP specimens were prepared and assigned to 1 of 5 experimental groups: Control (no surface treatment), Rocatec Plus (airborne‑particle abrasion with 110 µm silica‑coated alumina), Rocatec Soft (airborne‑particle abrasion with 30-µm silica‑coated alumina), Glass‑bead abrasion (40- to 70-µm spherical glass beads), and Signum Zirconia Bond (ceramic primer application). All specimens underwent thermocycling prior to shear bond strength testing with a self‑adhesive resin cement. Crystalline phase composition was quantified by X-ray diffraction (XRD) before and after 10⁶ mechanical cycles. Surface topography and chemical analysis were evaluated via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and 3-dimensional (3D) optical profilometry. Data were analyzed by 1-way ANOVA for shear bond strength and 2-way ANOVA for biaxial flexural strength, followed by the Tukey HSD post-hoc test (α=.05); Weibull analysis determined characteristic strength (σ₀) and modulus (m). Results All surface treatments significantly increased mean ±standard deviation shear bond strength (P<.001) compared with control (1.22 ±0.31 MPa): Rocatec Plus 19.9 ±3.7 MPa, Rocatec Soft 18.3 ±2.6 MPa, glass-bead abrasion 18.2 ±4.1 MPa, and Signum Zirconia Bond 15.4 ±5.7 MPa. Glass-bead abrasion preserved the highest tetragonal phase content (78%) before and after aging, whereas Rocatec Plus induced the greatest monoclinic transformation (9%). Rocatec Soft yielded the highest characteristic flexural strength (σ₀=1531.9 MPa; m=6.95) and the second highest monoclinic content, while glass-bead treatment showed high characteristic strength (σ₀=1240.1 MPa), greater scatter in Weibull distribution (m=5.30) and less surface damage. Conclusions Airborne-particle abrasion with angular particles increased Y-TZP biaxial flexural strength and tetragonal to monoclinic phase transformation. Glass bead abrasion enabled silicatization, achieved bond strength comparable to silica-coated alumina, and induced less phase transformation under the evaluated conditions.