Osteoblasts Generate Harder, Stiffer, and More Delamination‐Resistant Mineralized Tissue on Titanium Than on Polystyrene, Associated With Distinct Tissue Micro‐ and Ultrastructure

This study revealed that osteoblasts generate harder, stiffer, and more delamination‐resistant mineralized tissue on titanium than on the tissue culture polystyrene, associated with modulated gene expression, uniform mineralization, well‐crystallized interfacial calcium‐phosphate layer, and intensive collagen deposition. Knowledge of this titanium‐induced alteration of osteogenic potential leading to enhanced intrinsic biomechanical properties of mineralized tissue provides novel opportunities and implications for understanding and improving bone‐titanium integration and engineering physiomechanically tolerant bone. Introduction: Bone‐titanium integration is a biological phenomenon characterized by continuous generation and preservation of peri‐implant bone and serves as endosseous anchors against endogenous and exogenous loading, of which mechanisms are poorly understood. This study determines the intrinsic biomechanical properties and interfacial strength of cultured mineralized tissue on titanium and characterizes the tissue structure as possible contributing factors in biomechanical modulation. Materials and Methods: Rat bone marrow‐derived osteoblastic cells were cultured either on a tissue culture‐grade polystyrene dish or titanium‐coated polystyrene dish having comparable surface topography. Nano‐indentation and nano‐scratch tests were undertaken on mineralized tissues cultured for 28 days to evaluate its hardness, elastic modulus, and critical load (force required to delaminate tissue). Gene expression was analyzed using RT‐PCR. The tissue structural properties were examined by scanning electron microscopy (SEM), collagen colorimetry and localization with Sirius red stain, mineral quantification, and localization with von Kossa stain and transmission electron microscopy (TEM). Results: Hardness and elastic modulus of mineralized tissue on titanium were three and two times greater, respectively, than those on the polystyrene. Three times greater force was required to delaminate the tissue on titanium than that on the polystyrene. SEM of the polystyrene culture displayed a porous structure consisting of fibrous and globular components, whereas the titanium tissue culture appeared to be uniformly solid. Cell proliferation was remarkably reduced on titanium. Microscopic observations revealed that the mineralized tissue on titanium was composed of uniform collagen‐supported mineralization from the titanium interface to the outer surface, with intensive