Thermo and mechanical cycling and veneering method do not influence Y-TZP core/veneer interface bond strength

[محمد بهبهانی]

a b s t r a c t
Objectives: The purpose of this study was to evaluate the influence of thermal and mechanical
cycling and veneering technique on the shear bond strength of Y-TZP (yttrium oxide
partially stabilized tetragonal zirconia polycrystal) core–veneer interfaces.
Materials and methods: Cylindrical Y-TZP specimens were veneered either by layering (n = 20)
or by pressing technique (n = 20). A metal ceramic group (CoCr) was used as control (n = 20).
Ten specimens for each group were thermal and mechanical cycled and then all samples
were subjected to shear bond strength in a universal testing machine with a 0.5 mm/min
crosshead speed. Mean shear bond strength (MPa) was analysed with a 2-way analysis of
variance and Tukey’s test ( p < 0.05). Failure mode was determined using stereomicroscopy
and scanning electron microscopy (SEM).
Results: Thermal and mechanical cycling had no influence on the shear bond strength for all
groups. The CoCr group presented the highest bond strength value ( p < 0.05)
(34.72  7.05 MPa). There was no significant difference between Y-TZP veneered by layering
(22.46  2.08 MPa) or pressing (23.58  2.1 MPa) technique. Failure modes were predominantly
adhesive for CoCr group, and cohesive within veneer for Y-TZP groups.
Conclusions: Thermal and mechanical cycling, as well as the veneering technique does not
affect Y-TZP core–veneer bond strength.
Clinical significance: Different methods of veneering Y-TZP restorations would not influence
the clinical performance of the core/veneer interfaces.
a r t i c l e i n f o
Article history:
Received 27 June 2012
Received in revised form
27 November 2012
Accepted 4 December 2012
Keywords:
Zirconia
Porcelain
Shear bond strength
Mechanical cycling
Thermal cycling