Various designs of dental implants made of zirconium dioxide (zirconia) as an alternative to titanium implants are available as one-piece implant (OPI) or as bone-level or tissue-level two-piece implants (TPI) with either ceramic or titanium abutment screw types of implant-abutment connections. This study aimed to identify and quantify stress concentrations and levels across different zirconia implant designs under a quasi-static external load. The study used a finite element analysis (FEA) simulation model, including five zirconia implant design models of OPI and bone-level and tissue-level TPI zirconia implants with either ceramic or titanium abutment screw, to calculate and locate maximum principal (σ1) and minimum principal (σ3) and equivalent (von Mises) stresses under 400N of quasi-static loading at a 30-degree angle within ISO14801:2016 geometry and boundary conditions. The FEA assumed linear elastic and isotropic material properties. OPI showed high stress concentrations at the implant body’s external thread above the specimen holder. TPIs showed similar maximum principal stress (σ1) areas in their implant body, while minimum principal stress (σ3) occurred in the implant–abutment interface at the abutment neck, and the corresponding area in the implant platform. The TPIs with ceramic screws exhibited the highest stresses at the screw–abutment interface. Within the limitations of this study, under a static oblique load applied within the ISO 14801:2016 geometry condition, stress distributions differ between OPI and TPI. TPIs show lower stress within the implant body but higher stress transfer to the specimen holder compared with OPI. Tissue-level TPIs exhibit lower stress than bone-level designs, whereas stresses in the abutment and screw depend on screw design and material. TPIs with ceramic screws exhibit higher stress levels compared to titanium screw.
Gül et al. (Thu,) studied this question.