Effect of Changes in Sintering Temperature on the Flexural Strength of Multiphase Zirconia An In vitro study

Background: For decades dental research aimed at finding a material that presents a balance between strength and esthetics to satisfy patient demands. Dental zirconia stood out in terms of strength, but its main drawback was its opaqueness. Insistent dental research led to evolution of monolithic zirconia. Recently, multiphase zirconia was introduced into the market, offering a gradual transition in translucency as well as strength within the same blank. Sintering of zirconia is a key determinant for its final properties, however there are insufficient studies investigating the effect of changing sintering temperature on multiphase zirconia. Aim of the Study: The aim of this invitro study was to determine the effect of changes in sintering temperature on the flexural strength of multiphase zirconia. Materials and Methods: 45 multiphase zirconia blocks (IPS-e.max ZirCAD Prime) with dimensions 16mm x 12mm x 1.2mm were constructed. The samples were sectioned 20-25% larger than the desired final size to compensate sintering shrinkage. The samples were divided into 3 groups (n=15) according to their sintering temperature (1460 ℃,1530 ℃,1600 ℃) and holding time two hours. Flexural strength was measured using universal testing machine. Results were tabulated and statistically analysed. Results: No significant changes were found between different groups. The highest strength was measured in samples sintered at 1460 ℃ and the lowest strength was measured in samples sintered at 1600 ℃. Conclusion: E. max ZirCAD Prime multiphase zirconia can be sintered at temperatures 1460 ℃, 1530 ℃ and 1600 ℃ without compromising the flexural strength.