Effects of pretreatments and hydrothermal aging on biaxial flexural strength of lithium di-silicate and Mg-PSZ ceramics

ObjectivesTo evaluate the effect of specimen thickness, pretreatment and hydrothermal aging on the biaxial flexural strength (BFS) of lithium di-silicate glass (e.max Cad) and magnesia-stabilized zirconia (ZirMagnum) ceramic discs.MethodsThe e.max Cad discs was studied: i) crystallized, ii) crystallized and glazed and iii) crystallized, glazed and unglazed side etched with hydrofluoric acid. The ZirMagnum discs were studied: i) as delivered, ii) after sandblasting and iii) after heat treatment similar to veneering. Hydrothermal aging was simulated by autoclave treatment.ResultsThe BFS of all the ZirMagnum specimens was superior (p < 0.001) to all the e.max Cad specimens. Glazing the 0.4 mm e.max Cad discs reduced (p < 0.05) their BFS compared with the unglazed 0.8 mm specimens, whereas glazing of 0.8 mm discs had no influence (p > 0.05) on the strength. Etching and autoclaving of e.max Cad did not affect (p > 0.05) the BFS. For ZirMagnum sandblasting with 0.2 MPa or 0.6 MPa did not influence the biaxial flexural strength (p > 0.05), whereas heat treatment reduced (p < 0.01) the BFS of 0.6 MPa sandblasted ZirMagnum. Autoclaving reduced the strength (p < 0.05) compared with ZirMagnum as delivered, whereas autoclaving of the 0.6 MPa sandblasted and heat-treated specimens did not influence (p > 0.05) the BFS. Glazing, etching and sandblasting increased (p < 0.05) surface roughness.ConclusionsThe effects of glazing, heat treatment, aging and mechanical treatment of the materials evaluated should be considered since their strength could be affected.Clinical significanceMechanical properties of restorations made from prefabricated ceramic blocks could be affected of various treatments and could change over time.