Fracture resistance and crystal phase transformation of a one‐ and a two‐piece zirconia implant with and without simultaneous loading and aging—An <i>in vitro</i> study

Abstract

Abstract Objective To evaluate the influence of artificial aging on the transformation propagation and fracture resistance of zirconia implants. Methods One‐piece (with integrated implant abutment, 1P; regular diameter [4.1mm]; n = 16) and two‐piece (with separate implant abutment, 2P; wide diameter [5 mm]; n = 16) zirconia implants were embedded according to ISO 14801. A two‐piece titanium–zirconium implant (Ti‐Zr; 4.1 mm diameter) served as a control ( n = 16). One subgroup ( n = 8) of each system was simultaneously dynamically loaded (10 7 cycles; 98N) and hydrothermally aged (85°C, 58 days), 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. Results 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. Conclusions 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.

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