title: Effect of changes in sintering parameters on monolithic translucent zirconia.
abstract: OBJECTIVE
  Aim of this study was to evaluate the effect of different sintering parameters on color reproduction, translucency and biaxial flexural strength of monolithic zirconia.
  
  
  METHODS
  Translucent zirconia discs having 15mm diameter, 1mm thickness, and shade A3 were milled and divided according to the sintering temperatures (1460°C, 1530°C, and 1600°C) into three groups (n=30). Each group was later divided into three subgroups (n=10) according to the sintering holding time (1, 2, and 4h). Easyshade spectrophotometer (Vita, Bad Säckingen, Germany) was used to obtain the ΔE between the specimens and the shade A3. Mean ΔE values below 3.0 were considered "clinically imperceptible", ΔE values between 3.0 and 5.0 were considered "clinically acceptable" and ΔE values above 5.0 were considered "clinically unacceptable". Contrast ratio (CR) was obtained after comparing the reflectance of light through the specimens over black and white background. Biaxial flexural strength was tested using the piston-on-three balls technique in a universal testing machine.
  
  
  RESULTS
  Mean ΔE results ranged from 4.4 to 2.2. Statistically significant decrease in the Delta E was observed as the sintering time and temperature increased. CR decreased from 0.75 to 0.68 as the sintering time and temperature increased. No significant change in the biaxial flexural strength was observed.
  
  
  CONCLUSIONS
  Sintering zirconia using long cycles and high temperatures will result in reduction of ΔE and CR. Biaxial flexural strength is not affected by changes in the evaluated sintering parameters.
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Germany; Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Egypt. Electronic address: kebeid@proth.uni-kiel.de.
authors.forename: Kamal
authors.initials: K
authors.lastname: Ebeid
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wille
authors.affiliation: Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Egypt.
authors.forename: Amina
authors.initials: A
authors.lastname: Hamdy
authors.affiliation: Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Egypt.
authors.forename: Tarek
authors.initials: T
authors.lastname: Salah
authors.affiliation: Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Egypt.
authors.forename: Amr
authors.initials: A
authors.lastname: El-Etreby
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D003116:Color; D003764:Dental Materials / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D008027:Light; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D013053:Spectrophotometry / Q000295:instrumentation; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014961:X-Ray Diffraction; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003764:Dental Materials; D015040:Zirconium; C028541:zirconium oxide
keywords: Biaxial flexural strength; Ceramics; Dental materials; Translucency; Zirconia