Effect of changes in sintering parameters on monolithic translucent zirconia

• Published in: Dental materials 2014-12, Vol.30 (12), p.e419-e424
• Main Authors: Ebeid, Kamal, Wille, Sebastian, Hamdy, Amina, Salah, Tarek, El-Etreby, Amr, Kern, Matthias
• Format: Article
• Language: English
• Subjects: Advanced Basic Science; Biaxial flexural strength; Ceramics; Color; Dental materials; Dental Materials - chemistry; Dentistry; Disks; Flexural strength; Hardness; Hot Temperature; Light; Materials Testing; Microscopy, Electron, Scanning; Modulus of rupture in bending; Pliability; Reproduction; Shades; Sintering; Spectrophotometry - instrumentation; Stress, Mechanical; Surface Properties; Time Factors; Translucency; X-Ray Diffraction; Zirconia; Zirconium - chemistry; Zirconium dioxide
• ISSN: 0109-5641; 1879-0097
• DOI: 10.1016/j.dental.2014.09.003

Abstract Objectives 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 15 mm diameter, 1 mm 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 4 h). Easyshade spectrophotometer (Vita, Bad Säckingen, Germany) was used to obtain the Δ E between the specimens and the shade A3. Mean Δ E values below 3.0 were considered “clinically imperceptible”, Δ E values between 3.0 and 5.0 were considered “clinically acceptable” and Δ E 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 Δ E 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. Significance Sintering zirconia using long cycles and high temperatures will result in reduction of Δ E and CR. Biaxial flexural strength is not affected by changes in the evaluated sintering parameters.