Fracture resistance and crystal phase transformation of a one- and a two-piece zirconia implant with and without simultaneous loading and aging-An in vitro study.

Abstract

To evaluate the influence of artificial aging on the transformation propagation and fracture resistance of zirconia implants. One-piece (with integrated implant abutment, 1P; regular diameter [4.1mm]; n=16) and two-piece (with separate implant abutment, 2P; wide diameter [5mm]; n=16) zirconia implants were embedded according to ISO 14801. A two-piece titanium-zirconium implant (Ti-Zr; 4.1mm diameter) served as a control (n=16). One subgroup (n=8) of each system was simultaneously dynamically loaded (107 cycles; 98N) and hydrothermally aged (85°C, 58days), while the other subgroup (n=8) remained untreated. Finally, specimens were statically loaded to fracture. Potential crystal phase transformation was examined at cross sections using scanning electron microscopy (SEM). A multivariate linear regression model was applied for statistical analyses. The fracture resistance of 1P (1,117 [SD = 38] N; loaded/aged: 1,009 [60] N), 2P (850 [36] N; loaded/aged: 799 [84] N), and Ti-Zr implants (1,338 [205] N; loaded/aged: 1,319 [247] N) was not affected significantly by loading/aging (p=.171). However, when comparing the systems, they revealed significant differences independent of loading/aging (p≤.001). Regarding the crystal structure, a transformation zone was observed in SEM images of 1P only after aging, while 2P showed a transformation zone even before aging. After hydrothermal treatment, an increase of this monoclinic layer was observed in both systems. The Ti-Zr control implant showed higher fracture resistance compared to both zirconia implants. Loading/aging had no significant impact on the fracture resistance of both zirconia implants. The wide-body 2P zirconia implant was weaker than the regular body 1P implant.