title: Effects of pretreatments and hydrothermal aging on biaxial flexural strength of lithium di-silicate and Mg-PSZ ceramics.
abstract: To 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.
  
  
  
  The 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.
  
  
  
  The BFS of all the ZirMagnum specimens was superior (p<0.001) to all the e.max Cad specimens. Glazing the 0.4mm e.max Cad discs reduced (p<0.05) their BFS compared with the unglazed 0.8mm specimens, whereas glazing of 0.8mm 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 0.2MPa or 0.6MPa did not influence the biaxial flexural strength (p>0.05), whereas heat treatment reduced (p<0.01) the BFS of 0.6MPa sandblasted ZirMagnum. Autoclaving reduced the strength (p<0.05) compared with ZirMagnum as delivered, whereas autoclaving of the 0.6MPa sandblasted and heat-treated specimens did not influence (p>0.05) the BFS. Glazing, etching and sandblasting increased (p<0.05) surface roughness.
  
  
  
  The effects of glazing, heat treatment, aging and mechanical treatment of the materials evaluated should be considered since their strength could be affected.
  
  
  
  Mechanical properties of restorations made from prefabricated ceramic blocks could be affected of various treatments and could change over time.
authors.affiliation: Dental Materials Science, Faculty of Medicine, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: André
authors.affiliation: Dental Materials Science, Faculty of Medicine, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Wen
authors.initials: W
authors.lastname: Kou
authors.affiliation: Dental Materials Science, Faculty of Medicine, Umeå University, SE-901 87 Umeå, Sweden. Electronic address: Goran.Sjogren@umu.se.
authors.forename: Göran
authors.initials: G
authors.lastname: Sjögren
authors.affiliation: Research and Development, Cad.esthetics AB, SE-931 21 Skellefteå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Sundh
mesh_terms: D002516:Ceramics; D003776:Dental Porcelain; D006801:Humans; D008094:Lithium; D008422:Materials Testing; D018583:Pliability; D017640:Silicates; D013499:Surface Properties; D015040:Zirconium
chemical_list: D017640:Silicates; D003776:Dental Porcelain; D008094:Lithium; D015040:Zirconium
keywords: Accelerated aging; CAD/CAM; Ceramic; Magnesia-stabilized zirconia