Comparison of Tantalum and Hydroxyapatite Coatings on Titanium for Applications in Load Bearing Implants

Over the years hydroxyapatite (HA) coatings have been used to improve biologic properties of Ti‐based load bearing metal implants. However, applicability of HA coated implants is subjected to physical stability of the HA phase and mechanical integrity of the coating‐substrate interface. In this study, we have compared the microstructure and in vitro cell–materials interactions of newly developed laser deposited Ta coatings and radio frequency (RF) induction plasma sprayed HA coatings on Ti substrate. In vitro biocompatibility study, using human osteoblast cell line hFOB, showed equally excellent cellular adherence and growth on Ta and HA coatings. Quantitative assay of cell survivability on these coatings showed that the Ta coatings provide comparable initial cell attachment to that of HA coatings. Microstructural analysis of the coatings showed strong metallurgical bonding without sharp interface between the Ta coating and the Ti substrate, while the interface between HA coating and the Ti substrate was sharp. The interface microstructural features and in vitro cell–materials interactions of Ta coatings on Ti clearly demonstrate their potential to replace HA based coatings for enhanced/early biologic fixation. Other significant benefits of these dense Ta coatings include high toughness, strong bonding with the substrate, and long‐term stability of the interface.