FIGURE 3.

Schematic diagram illustrating the promotion of bone formation by incorporating Sr²⁺ on the surface of titanium-based materials. The incorporation of Sr²⁺ has a dual effect: firstly, it promotes the adhesion and proliferation of osteoblasts by activating the classical Wnt/β-catenin signaling pathway. This activation increases the expression of proteins and growth factors such as alkaline phosphatase (ALP), bone sialoprotein (BSP), osteocalcin (OCN), osteopontin (OPN), insulin-like growth factor (IGF), transforming growth factor (TGF), fibroblast growth factor (FGF), stimulating osteogenic differentiation and mineralization of osteoblasts, ultimately promoting bone formation. Secondly, Sr²⁺ regulates osteoclast differentiation through the RANK/RANKL axis, inhibiting the expression of osteoclast-associated genes like tartrate-resistant acid phosphatase (TRAP), matrix metalloproteinase (MMP9), and activated T-nuclear factor c1 (NFATc1), thereby suppressing bone resorption driven by osteoclasts.