Probing the interfacial strength of novel multi-layer zirconias

Marina R. Kaizer, Nantawan Kolakarnprasert, Camila Rodrigues, Herzl Chai, Yu Zhang

Research output: Contribution to journalArticlepeer-review


Objectives: The rapidly increasing use of zirconia-based CAD/CAM multi-layer structures in dentistry calls for a thorough evaluation of their mechanical integrity. This work examines the effect of the multi-layering architecture as well as variations in composition and inclusion of pigments among the layers on the flexural strength of multi-layer zirconias. Methods: A modified 4-point bending test, aided by a Finite Element Analysis (FEA), was used to probe the interfacial strength of 3 classes of yttria-partially-stabilized zirconia: Ultra Translucent Multi-Layer (UTML—5Y-PSZ), Super Translucent Multi-Layer (STML—4Y-PSZ), Multi-Layer (ML—3Y-PSZ). In accord with the size limitation (22-mm height) of CAD/CAM pucks, test samples were prepared in the form of “long” (25 × 2 × 3 mm) and “short” (17.8 × 1.5 × 2 mm) beams. Homogeneous beams (both long and short) were produced from either the Enamel (the lightest shade) or Dentin (the darkest shade) layer, whereas multi-layer beams (short beam only) were obtained by cutting the pucks along their thickness direction, where the material components of various shades were stacked. Results: The Enamel and Dentin layers exhibited similar flexural strength for a given material class, with ML amassing the highest strength (800–900 MPa) followed by STML (560–650 MPa) and UTML (470–500 MPa). The 3 classes of multi-layer zirconia showed a trade-off between strength and translucency, reflecting different yttria contents in these materials. The failure stress of the cross-sectional multi-layer beams was, however, ∼30% lower than that of their Enamel or Dentin layer counterparts, regardless of material tested. Significance: The weakness of interfaces is a drawback in these materials. Additionally, when measuring strength using short beam flexure, friction between the specimen and supporting pins and accuracy in determining loading span distances may lead to major errors.

Original languageEnglish (US)
Pages (from-to)60-67
Number of pages8
JournalDental Materials
Issue number1
StatePublished - Jan 2020


  • 4-point bending
  • Ceramic
  • Friction coefficient
  • Multi-Layer beam
  • Polychromatic
  • Short beam flexure
  • Zirconia

ASJC Scopus subject areas

  • General Materials Science
  • General Dentistry
  • Mechanics of Materials


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