Rapid Osseointegration Bestowed by Carbonate Apatite Coating of Rough Titanium

Titanium (Ti) implants that realize rapid osseointegration are required for favorable outcomes. Rough implant surfaces favor osseointegration, hence, coating implants with natural bone mineral, i.e., carbonate apatite (CO 3 Ap), may be effective for osseointegration. To achieve rapid osseointegration, rough‐Ti substrates are coated with CO 3 Ap (CO 3 Ap‐Ti) and the effects are evaluated in vitro and in vivo. For comparison, rough‐Ti without coating (rough‐Ti) and calcite‐coated rough‐Ti (calcite‐Ti) substrates are fabricated. The adhesive strengths of calcite and CO 3 Ap to the substrates are ≈56.6 and ≈76.8 MPa, respectively, being significantly higher than the strength defined in ISO13779‐2 (15 MPa). Calcite and CO 3 Ap coatings significantly promote preosteoblastic MC3T3‐E1 cell proliferation. Additionally, the CO 3 Ap coating promotes higher osteogenic differentiation activity than the calcite coating. Implantation of CO 3 Ap‐Ti into rabbit tibia defects prompts bone maturation, compared to calcite‐Ti or rough‐Ti implantation. The bone‐implant contact percentage with CO 3 Ap‐Ti and calcite‐Ti is higher than that with rough‐Ti. Consequently, CO 3 Ap‐Ti acquires a robust bond with the host bone at an early stage (4 weeks postimplantation), compared to calcite‐Ti or rough‐Ti: the CO 3 Ap‐Ti–bone bonding strength is ≈1.9‐ and ≈5.5‐fold higher than that of calcite‐Ti and rough‐Ti, respectively. Thus, CO 3 Ap coating of Ti implants effectively achieve rapid osseointegration.