IADR Abstract Archives
Flexural Strength of Yttria-Gradient Multilayered Zirconia
Objectives: This study investigates multilayered zirconia with varying yttria content, which closely mimics the shade and translucency gradient of natural teeth. Yttria-gradient material typically includes a 3Y-TZP “dentin” layer and a 4Y to 5Y-PSZ “enamel” layer, with a transitional layer in between. Since restorations milled from these blanks will have a yttria-gradient, this study aims to evaluate the flexural strength across the layers of different yttria-gradient multilayered zirconia.
Methods: Flexural strength was determined for three yttria-gradient multilayered zirconia: Katana YML (YML) (Kuraray Noritake, Japan), E.max ZirCAD Prime (EZP) (Ivoclar Vivadent, Liechtenstein), and LayZir (LZ) (Smart Dentistry Solutions Inc., USA), compared to a control Katana HTML (HTML). Due to the necessity of incorporating all layers, standard ISO 18672(2015) size bars were unsuitable for multilayer materials. Custom bars (54mm x 5mm) were fabricated to match the full thickness of each material (14.75mm to 18.02mm). Bars were sectioned using a high-speed saw, polished, and sintered according to manufacturer guidelines. Only the “enamel” layer was polished to a mirror-like finish to mimic the clinical scenario. Three-point flexural strength testing was performed with the “enamel” layer in compression to replicate clinical situation, using an Instron Model 5566A at a crosshead speed of 1.0mm/min. ANOVA and Tukey’s test were utilized to determine significant differences.
Results: Preliminary results from three-point bending test with "enamel" layer in compression and "dentin" layer in tension indicated that LZ has the highest flexural strength at 474.33MPa, followed by EZP, YML, and HTML. All groups, except the control, exhibited high variability in flexural strength values.
Conclusions: Yttria-gradient multilayered zirconia may demonstrate less predictable results compared to shade-gradient zirconia due to differences in material composition and crystalline structures across layers. Testing the predominant middle section of yttria-gradient multilayered zirconia could provide representative values.
Methods: Flexural strength was determined for three yttria-gradient multilayered zirconia: Katana YML (YML) (Kuraray Noritake, Japan), E.max ZirCAD Prime (EZP) (Ivoclar Vivadent, Liechtenstein), and LayZir (LZ) (Smart Dentistry Solutions Inc., USA), compared to a control Katana HTML (HTML). Due to the necessity of incorporating all layers, standard ISO 18672(2015) size bars were unsuitable for multilayer materials. Custom bars (54mm x 5mm) were fabricated to match the full thickness of each material (14.75mm to 18.02mm). Bars were sectioned using a high-speed saw, polished, and sintered according to manufacturer guidelines. Only the “enamel” layer was polished to a mirror-like finish to mimic the clinical scenario. Three-point flexural strength testing was performed with the “enamel” layer in compression to replicate clinical situation, using an Instron Model 5566A at a crosshead speed of 1.0mm/min. ANOVA and Tukey’s test were utilized to determine significant differences.
Results: Preliminary results from three-point bending test with "enamel" layer in compression and "dentin" layer in tension indicated that LZ has the highest flexural strength at 474.33MPa, followed by EZP, YML, and HTML. All groups, except the control, exhibited high variability in flexural strength values.
Conclusions: Yttria-gradient multilayered zirconia may demonstrate less predictable results compared to shade-gradient zirconia due to differences in material composition and crystalline structures across layers. Testing the predominant middle section of yttria-gradient multilayered zirconia could provide representative values.