Warpage and Flexural Strength in Multilayered and Monolithic Zirconia
Objectives: Analyze the warpage and flexural strength of translucency and chroma multilayered and monolithic zirconia materials with various dimensions of specimens for flexural strength testing.
Methods: Three groups of materials were included in this study: (i) Multilayer by chroma and translucency: Origin Beyond Plus Hybrid (B&D Dental) and LayZir All Indication (Smart Dentistry Solutions); (ii) Multilayer by chroma: VITA YZ ST Multicolor (Vita Zahnfabrik); and (iii) Monolithic: VITA YZ T (Vita Zahnfabrik). Rectangular bar specimens of each material were prepared with dimensions of 50Χ14Χ1.5 mm (Large-1.5H, n=10), 50Χ14Χ4 mm (Large-4H, n=5), and 15Χ3.5Χ1.5 mm (Small-15L, n=10), and 25Χ3.5Χ1.5 mm (Small-25L, n=10) using a Buehler IsoMet 5000 Precision Saw. All specimens were sintered per the manufacturer’s instructions. Each specimen was placed on a Starrett 384W Steel Parallel block with a parallel tolerance of 2.5 mm to measure the thickness with a Mitutoyo Electronic Drop Indicator. A total of 18 readings were taken for each specimen: three readings at each position (left, middle and right) by each side (front and back). Warpage was calculated in percentage of the central clearance by the bar length, flatness by reading was calculated in the length direction. Three-point bend test was performed using a fully articulated test fixture on a Universal Testing Machine (Instron 5566A). The effect of bar size on warpage and flexural strength was analyzed by one-way ANOVA followed by Tukey HSD test.
Results: The warpage and flexural strength of multilayered and monolithic zirconia materials with different specimen dimensions were shown in Table 1.
Conclusions: Warpage for large and thin bars is significantly higher than small and thick bars; For multilayered zirconia, the large bar has a significantly lower flexural strength than the small bar. Flexural strengths between two tested materials has no significant different. For monolithic zirconia, there is no significant difference in flexural strength between large bars and small bars.