Recent Advances in pH-Responsive Coatings for Orthopedic and Dental Implants: Tackling Infection and Inflammation and Enhancing Bone Regeneration

Bone is a structurally complex and dynamic tissue that plays a crucial role in mobility and skeletal stability. However, conditions such as osteoporosis, osteoarthritis, trauma-induced fractures, infections, and malignancies often necessitate the use of orthopedic and dental implants. Despite significant progress in implant biomaterials, challenges such as bacterial infection, inflammation, and loosening continue to compromise implant longevity, frequently leading to revision surgeries and extended recovery times. Smart coatings have emerged as a next-generation solution to these problems by providing on-demand, localized therapeutic responses to microenvironmental changes around implants and promoting bone regeneration. Such coatings can minimize antibiotic resistance by enabling controlled, stimulus-triggered drug release. Although the idea of using pH-sensitivity as a tool to make smart coatings is not a new thought, there are no options currently good enough to enter clinical studies. This review provides a comprehensive overview of recent advances in pH-sensitive polymers, hybrid composites, porous architectures, and bioactive linkers designed to dynamically respond to pathological pH variations at implant sites. By investigating the mechanisms of action, antibacterial and anti-inflammatory effects, and roles in bone regeneration, it is shown that the ability to provide time-dependent drug release for both short-term and long-term infections, as well as keeping the environment welcoming to the bone cell growth and replacement, is not an easy goal to reach, even with a fully biocompatable, non-toxic, and semi-biodegradable (one that releases the drug, but does not fade away) coating material compound. Reviewing all available options, including their functions and failures, finally, emerging trends, translational barriers, and future opportunities for clinical implementation are highlighted, underscoring the transformative potential of bioresponsive coatings in orthopedic and dental implant technologies.