Abstract
<title>Abstract</title> <p>This laboratory study evaluated the effect of different surface pretreatment protocols on surface roughness, surface topography, elemental composition, shear bond strength (SBS), and failure modes of two multi-layered monolithic partially stabilized zirconia materials (Katana STML and Cercon xt ML), single versus double application of an MDP-containing primer was also evaluated. The study aimed to clarify the balance between bond strength enhancement and preservation of zirconia structural integrity. A total of 160 specimens were randomly assigned to four groups: no treatment (control), Er,Cr:YSGG laser irradiation (6 W), airborne-particle abrasion (grit-blasting) with < 50 µm Al₂O₃, and lithium silicate coating followed by 9.5% hydrofluoric acid etching for 100 s (n = 20). Surface characteristics were analyzed using SEM and EDX. Specimens received either a single or a double primer application (Monobond N). Resin cement cylinders (2 mm × 3 mm) were fabricated, stored at 37°C for 24 h, thermocycled (10,000 cycles), and tested for SBS. Failure modes were assessed microscopically. Data were analyzed using ANOVA and Welch’s t-tests (α = 0.05). Airborne-particle abrasion demonstrated the highest SBS values (6.87 ± 0.58 MPa) and (8.87 ± 1.74 MPa), whereas laser-treated groups showed the lowest (2.73 ± 0.31 MPa) and (2.75 ± 0.40 MPa) for Katana STML and Cercon xt ML, respectively. The Lithium disilicate coating and control groups had comparable intermediary values. Surface pretreatment and material type significantly influenced bond strength (p < 0.001) and (p = 0.04), respectively, while primer application was not significant. Double primer application did not improve bond strength; although notable interaction with surface pretreatment was observed, its effect was limited.</p>