Assessing the Osteogenic Potential of Zirconia and Titanium Surfaces with an Advanced in Vitro Model

Objectives: In recent years, zirconia dental implants have gained increased attention especially for patients with thin gingival biotypes or patients seeking metal-free restoration. While physical and chemical material surface properties govern the blood-material interaction and subsequent osseointegration processes, the organizational principles underlying the interplay of biochemical and biophysical cues are still not well understood. Therefore, this study investigated how the interaction of a microstructured zirconia surface with blood influences its osseointegration potential compared to microstructured titanium with or without additional nanostructures.

Methods: Microstructured zirconia and micro- (and nano)structured titanium surfaces were fabricated via sandblasting followed by acid etching and their topographical as well as physico-chemical features were thoroughly characterized. Following, an advanced in vitro approach mimicking the initial blood interaction of material surfaces upon implantation was applied. Fibrinogen adsorption, human blood coagulation as well as their influence on cell fate decisions of primary human bone and progenitor cells (HBC) were studied.

Results: Obtained surface micro- and nanostructures on titanium surfaces were sharp with rugged peaks whereas zirconia surfaces were less rough with structures being shallower, more round and granular. Compared to titanium surfaces, the zirconia surface showed increased fibrinogen adsorption, higher levels of total accessible fibrinogen γ-chain moieties yielding in increased platelet adhesion and activation and consequently thrombogenicity. Mineralization of HBC on microstructured surfaces was significantly higher on zirconia than on titanium, but was significantly lower compared to titanium surfaces with nanostructures.

Significance: This study provides insights into blood-material interaction and subsequent cellular events that are important for implant surface development.