Effect of Hydroxyapatite Coating Thickness on Inflammation and Osseointegration of Ti-29Nb-13Ta-4.6Zr (TNTZ) implants

The study investigated the effect of hydroxyapatite (HA) coating thickness on the inflammation and osseointegration properties of Ti-29Nb-13Ta-4.6Zr (TNTZ) implants for orthopedic implant applications. TNTZ screws were used as based samples, and the HA coating was deposited using an electrophoretic deposition (EPD) method to achieve various coating thickness. The thin (50-70 µm), medium (70-90 µm), and thick (90-110 µm) coating thicknesses were obtained by applying different voltage and time exposure during the EPD process, while the uncoated screw was used as the control sample. The screws were implanted into the right tibia of male Rattus norvegicus Wistar rats for two weeks. After termination of the test animals, blood samples were collected to measure levels of tumor necrosis factor-α (TNF- α) using an ELISA method, and a removal torque test was performed on the implanted screws. Additionally, tibial bone tissue around the implant area was collected for histopathology analysis. The result of the study indicated that HA coating thickness has effects on TNF-α concentration, removal torque value, and new bone growth. The optimal thickness of the HA layer was found to be in the medium range (70-90 µm), resulting in low inflammation levels, relatively high osseointegration rates, and optimal new bone tissue growth. These finding were expected to be applicable in future orthopedic implant applications.