Influence of luting space of zirconia abutment on marginal discrepancy and tensile strength after dynamic loading

Abstract

Statement of problem: Although luting space is related to the marginal fit of indirect restorations, information on its influence on the marginal fit and tensile strength of zirconia abutments bonded to titanium bases is lacking.

Purpose: The purpose of this in vitro study was to evaluate the influence of luting space on the marginal discrepancy and tensile strength of zirconia abutments bonded to a titanium base after dynamic loading.

Material and methods: Ninety implant replicas were embedded in resin blocks to attach 4-mm-high titanium luting bases. Zirconia abutments (Ceramill Zolid FX) were fabricated with different internal luting spaces: 25 μm (G25), 50 μm (G50), or 75 μm (G75). The zirconia abutments were cemented on the titanium bases by using a resin cement (Panavia F 2.0) under a constant load of 20 N. The marginal discrepancy and internal fit of 10 random specimens from each group were evaluated with a stereoscopic microscope at ×50 magnification. The remaining specimens were submitted to the tensile strength test in which half were evaluated after dynamic loading (1.2 million cycles of 200 N at 3.8 Hz) in a mechanical fatigue machine. The tensile strength test was performed using a pullout apparatus coupled to a universal testing machine at a crosshead speed of 0.5 mm/min. The mode of failure was determined by observation at ×50 magnification under a stereomicroscope and classified into adhesive or mixed. The groups were compared by using 2-way ANOVA and the Tukey HSD test (α=.05).

Results: Increase in the luting space did not influence the marginal discrepancy (P>.05). All zirconia abutments exhibited lower pullout strength after fatigue simulation (P<.05). G75 demonstrated lower tensile strength than G25 and G50 before and after loading (P<.05). Most failures were adhesive at the zirconia-cement interface.

Conclusions: The increase of the luting space to 75 μm did not influence marginal discrepancy; however, it reduced the tensile strength of a zirconia abutment bonded to a titanium base.