Comparing fracture resistance of CAD/CAM polyetherketoneketone ″PEKK″, carbon reinforced polyetheretherketone ″CR PEEK″ and nano-zirconia implant abutments receiving digitally milled nano-zirconia and glass ceramic crowns: an in vitro study

Abstract The presented in vitro study aimed to evaluate the fracture resistance of implant-supported systems with different combinations of abutment–crown materials, namely: Computer-Aided Design/ Computer-Aided Manufacturing ″CAD/CAM″ Nano-zirconia ″NZr″, carbon reinforced polyetheretherketone ″CR PEEK″ and polyetherketoneketone ″PEKK″ dental implant abutments were coronally restored by digitally milled monolithic lithium disilicate ″MLD″ as a type of glass-ceramic ″GC″ and Nano-zirconia ″NZr″ crowns following a thermomechanical aging protocol. Materials and methods A total of 60; Nano-zirconia ″NZr″, carbon reinforced polyetheretherketone ″CR PEEK″, and polyetherketoneketone ″PEKK″ maxillary premolar abutments with titanium base were distributed into three equal groups ( n = 20). Each group was divided according to the fabricated and cemented CAD/CAM milled crown into two equal subgroups: Nano-zirconia ″NZr″ and monolithic lithium disilicate ″MLD″ ( n = 10). The ceramic crowns were surface treated and cemented to the abutments by applying the recommended adhesive resin cement. Those study specimens underwent thermo-mechanical aging (49 N, 1.2 × 10 6 cycles, 5–55 °C). Afterward, the fracture resistance test was performed, and the statistical analyses were made for all subgroups using two-way (ANOVA) analysis of variance and the Tukey post hoc tests ( α = 0.05). Results Nano-zirconia implant abutments cemented to NZr crowns exhibited the highest fracture resistance values of all subgroups. In addition, ″CR PEEK″ implant abutments reported higher fracture resistance values than those of ″PEKK″. Within each implant abutment group ″NZr″ crowns demonstrated significant high fracture resistance values over their ″MLD″ counterparts ( p < 0.0001). Conclusions Considering limitations of the presented in vitro study, after thermomechanical aging, recently introduced ″NZr″ implant abutments exhibited higher fracture resistance than ″CR PEEK″ that again reported higher fracture resistance than ″PEKK″ abutments. Generally, all abutment materials might withstand the physiologic occlusal forces. Information about the long-term survival of these recently studied implant abutments types seems limited.