Effect of Zirconia Core Thickness and Veneer Firing Cycle on the Biaxial Flexural Strength of Veneering Ceramic.
PURPOSE
To evaluate the influence of various Y-TZP thicknesses and veneer firing cycles on the strength of two ceramic veneers.


MATERIALS AND METHODS
180 Y-TZP cores of 0.5, 1.0, and 5.0 mm thickness were prepared followed by sintering in a high temperature furnace; 180 presintered veneering ceramic discs (Vita VM9 porcelain and e.max Ceram) were also prepared using a mold. The discs were placed on zirconia plates (zirconia cores) of different thickness (0.5, 1.0, and 5.0 mm) and exposed to different firing cycles (Vita VM9 porcelain-910, 930, and 950°C; e.max Ceram-750, 770, and 790°C). Ball-on-three-balls flexural strength test was performed (universal testing machine) at a crosshead speed of 0.5 mm/min. Scanning electron microscopy of fractured specimens was performed. Means and standard deviations of flexural strength were analyzed using Tukey-Kramer HSD test for multiple comparisons.


RESULTS
Specimens within material groups showed no significant difference (p > 0.05) for flexural strength with respect to Y-TZP core thickness (0.5, 1.0, and 5.0 mm) (VM9 [117.30 ± 14.328, 117.75 ± 13.66, 113.75 ± 20.10], e.max Ceram [94.79 ± 17.5, 100.02 ± 14.7, 95.23 ± 15.4]). Flexural strength within material groups with respect to different firing cycles ([VM9-910, 930, 950°C], e.max Ceram [750, 770, 790°C]), for VM9 (111.49 ± 15.7, 120.86 ± 13.2, 116.46 ± 18.4), and e.max Ceram (94.64 ± 15.2, 101.6 ± 16.69, 93.8 ± 15.20) showed no significant difference (p > 0.05).


CONCLUSIONS
Different zirconia thicknesses (0.5, 1.0, and 5.0 mm) and veneer firing cycles for Vita VM9 and e.max ceramics failed to show any significant influence on their biaxial flexural strengths.
['Alayad|Abdullah Saeed|AS|']
D002516:Ceramics D003776:Dental Porcelain D003799:Dental Stress Analysis D003801:Dental Veneers D000077298:Flexural Strength D008422:Materials Testing D013499:Surface Properties D015040:Zirconium
core thickness firing cycle flexural strength veneering ceramic Bilayered zirconia