Title: 0707 - Effect of Shading on Flexural Strength of Cubic Full-Contour Zirconia
Bjoern Theelke (Presenter)
3M Oral Care
Rainer Dittmann, 3M Oral Care
Holger Hauptmann, 3M Oral Care
Objectives: In this study the flexural strength of a gradient shaded cubic full-contour zirconia ceramic was investigated. Shades from light to dark were tested to evaluate if coloring has an impact on mechanical properties.
Methods: The investigated materials were 3M Lava Esthetic Fluorescent Full-Contour Zirconia Discs in the shades A1, A3.5, B2, C4 and D3.
Bending bars were cut from pre-sintered blanks, chamfered, smoothened with P2500 sandpaper and sintered to final dimensions of 18x4x1.2mm.
Surface of samples for flexural strength testing was “as fired” without further preparation in sintered state.
The bending bars were loaded until fracture in a 3-point-bending setup with 12 mm load span and 1 mm/min load speed.
The flexural strength test has been performed in accordance to ISO6872:2015 recommendations. Mean flexural strength and standard deviation was calculated. 2-sample t-tests (0.95) were performed between all groups.
Results: Measurement results are summarized in table 1.
All shades show mean flexural strength values above 800 MPa and there is no statistical significant difference between the tested groups (p > 0.116).
Conclusions: Due to the phase composition cubic zirconia ceramics have lower flexural strength compared to tetragonal zirconia which typically offers above 1000 MPa. The cubic crystal phase content is determined by stabilizing additives like Yttria but might also be changed by shading elements. For cubic zirconia it is important to ensure that incorporated shading elements have no detrimental effect on mechanical properties. For the investigated material light shades as well as intense shades offer an equivalent strength level.
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The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: I am employee of 3M.