A critical review and finite element study of structural relaxation in veneered 3Y-TZP dental structures
Abstract
Yttria stabilized Tetragonal Zirconia Polycrystal (3Y-TZP) materials veneered with porcelain are preferred for clinical practice due to their bio-functionality, biocompatibility, and affordability. However, these materials are often subjected to premature clinical failures due to combination of subsurface flaws and tensile stresses within porcelains. This work focuses on performing a critical literature review and evaluating veneer characteristics, i.e. structural relaxation, to form a suitable explanation for the development of subsurface stresses. User material subroutines, UEXPAN and UTRS are developed, validated and integrated in ABAQUS finite element solver. With the use of validated models, it is shown that faster cooling rates and high veneer thickness results in higher subsurface tensile stresses due to lack of structural relaxation. Slow cooling rates and lower veneer thickness result in desired compressive stresses in the subsurface. This work shows that structural relaxation in veneer can be used for tailoring the desired stress for the extending lifespan of veneered 3Y-TZP dental restorations.