Influence of Dentin Bonding and Interfacial Adhesion on the Flexural Properties of a 4 Mol% Yttria Partially Stabilized Zirconia.

Abstract

Purpose: 4 mol% yttria partially stabilized zirconia (4Y-PSZ) offers improved translucency compared to 3% tetragonal polycrystalline zirconia but lacks transformation toughening, which may affect its flexural strength. Since adhesive luting was shown to improve mechanical performances of all-ceramic materials, this research evaluated the influence of different cements on the 3-point flexural strength of a 4Y-PSZ bonded to bovine dentin.

Materials and methods: Thirty 1-mm-thick dentin slices were obtained from bovine incisors, paired with 1-mm-thick 4Y-PSZ slices, then divided into three groups (n=10) based on the cement investigated: a 10-MDP-free self-adhesive resin cement (SA), a 10-MDP-based adhesive resin cement (MDP-A), and a conventional glass ionomer cement (GI). After luting, the obtained assemblies were cut to obtain 1-mm-wide bar-shaped specimens, which were subjected to 3-point bending test. Fracture loads and flexural strength were recorded, and the modes of failure were analyzed.

Results: The highest fracture load and flexural strength were observed in the MDP-A group (76.5 N and 401.5 MPa), followed by the SA group (62.3 N and 326.8 MPa). The GI group exhibited the lowest values (45.6 N and 239.5 MPa). In MDPA group samples predominantly exhibited concurrent dentin and zirconia fractures without debonding, while in SA and GI groups a frequent incidence of debonding at the interface was observed.

Conclusion: Adhesive cementation enhances the flexural strength of 4Y-PSZ bonded to bovine dentin, with the 10-MDP-based resin cement yielding the best performances. Effective adhesive techniques could improve the mechanical performance of 4Y-PSZ restorations, making them more reliable for clinical applications.