Long-term Bone Response to Titanium Implants Coated with Thin Radiofrequent Magnetron-Sputtered Hydroxyapatite in Rabbits

Purpose: The present study was designed to investigate the long-term bone response around machined screw-type uncoated and calcium phosphate (CaP) -coated commercially pure titanium implants. Materials and Methods: Using a magnetron sputtering technique, implants with a CaP coating similar in composition and CaP ratio to hydroxyapatite were produced. Heat treatment was subsequently used to increase the crystallinity of the coatings. Four types of coatings (0.1 and 2.0 µm amorphous and 0.1 and 2.0 µm crystalline) were manufactured; uncoated implants served as a control. Three hundred twenty implants (64 of each type) were randomly placed in the tibial cortical and trabecular femoral bones of 40 rabbits. The rabbits were sacrificed 9 months after implant placement. Results: Histomorphometric evaluation carried out on ground sections revealed that the crystalline CaP coatings achieved the highest bone-implant contact in both tibiae and femora compared with amorphous CaP-coated and uncoated titanium. Discussion: The present study suggests that submicron crystalline hydroxyapatite coating adds bioactive properties to titanium oral implants. Conclusion: An ultra-thin, 0.1- µm crystalline CaP coating can elicit and maintain an improved long-term bone response compared to amorphous coated or uncoated Ti implants, without any adverse tissue reactions. (More than 50 references.)