Hydroxyapatite-Based Alendronate Coatings for Local Drug Delivery and Implant Osseointegration

Background/Objectives: Hydroxyapatite (HA) coatings offer an osteoconductive interface and a mineral reservoir for alendronate. Their pharmaceutical value depends on whether binding produces biologically available exposure without impairing healing. This review examines that relationship in HA–alendronate coatings on titanium. Methods: A structured critical narrative review used PubMed/MEDLINE, Scopus and Web of Science Core Collection, with reference-list screening. Screening identified 62 primary studies; contextual literature supported mechanistic and translational interpretation. Results: Adsorption, mineral incorporation, laser deposition and hybrid reservoirs produce different loading and release profiles. Cell and animal findings depend on formulation, dose, comparator and model. Mineral content, bone-to-implant contact and mechanical fixation provide complementary evidence and are not interchangeable outcomes. Human studies have mainly evaluated other bisphosphonates in fibrinogen coatings or alendronate applied as a gel around dental implants. Some reported less marginal bone loss, but improvements in implant stability were inconsistent. These results do not directly establish the efficacy of HA–alendronate coatings. Conclusions: Translation requires reproducible manufacture, measured active-drug availability, preserved physiological remodeling, durable coating adhesion and controlled trials for a defined implant indication. Strong mineral binding alone does not establish effective local therapy.