João Vitor do Nascimento Santos, Sarah Emille Gomes da Silva, Helena Nóbrega Almeida, Tiago Moreira Bastos Campos, Estevam Augusto Bonfante, Yu Zhang, Rodrigo Othávio de Assunção E Souza
The borosilicate glass coating improved the mechanical strength of both zirconia generations without significantly affecting their physical and surface properties under the conditions of this in vitro study. These findings support its potential as a surface treatment strategy, although further validation is required.
OBJECTIVES: To evaluate the effect of a borosilicate glass coating on the mechanical, surface and chemical properties of multilayer and 4Y-PSZ zirconia, after mechanical fatigue.
METHODS: Disc-shaped (13 mm×1.2 mm) sintered specimens were obtained from two types of commercial dental zirconia: structural multilayer (4 / 5Y-PSZ) (ML) and 4Y-PSZ (4Y) (Sagemax Corp.). Specimens (n = 15) were assigned to four surface treatments: control (Ctrl - silane only), airborne-particle abrasion + silane (AL), tribochemical silica coating + silane (SI), and application of borosilicate-based glass + hydrofluoric acid + silane (BG). Surface roughness (Sa) was carried out. After dual-cure resin cement application, specimens underwent mechanical fatigue (1.2 ×106 cycles, 295 N, 4 Hz). Microstructure and phase composition were analyzed using Scanning Electron Microscopy (SEM), Energy dispersive x-ray (EDS) and X-Ray Diffraction (XRD). The biaxial flexural strength (BFS) was evaluated. Data were analyzed using two-way ANOVA and Tukey's test (α=0.05).
RESULTS: BFS was significantly affected by the surface treatments (p < 0.0001). BG showed the highest BFS (763.2 A MPa), followed by SI (688.4B), AL (595.3 C), and Ctrl (583.0 C). Surface roughness (Sa, µm) ranged from AL (0.33 A), SI (0.26B), Ctrl (0.08 C), BG (0.05D) in both zirconia. EDS revealed increased Si and Ca in BG; fracture analysis showed more homogeneous crack propagation in BG and intergranular patterns in AL. XRD indicated predominant tetragonal/cubic phases with minor monoclinic content, slightly higher in ML.
SIGNIFICANCE: The borosilicate glass coating improved the mechanical strength of both zirconia generations without significantly affecting their physical and surface properties under the conditions of this in vitro study. These findings support its potential as a surface treatment strategy, although further validation is required.