Titanium surface modified by hydroxyapatite coating for dental implants

The purpose of this study is to obtain a favorable combination of biocompatibility and mechanical properties for dental implants by developing process parameters for plasma-sprayed hydroxyapatite (HA) coating on titanium (Ti-6Al-4V ELI) surfaces. The plasma spraying experiments in this study, involving different process parameters of HA coating (coating thickness up to approximately 120 μm), are divided into four stages. An immersion test for the HA coatings in a simulated body fluid (SBF) was performed after HA coating. After 28 days, the crystallinity level of the HA coatings in the SBF increased from 54.88% to 74.39%, and the released calcium ion concentration increased from 44.9 ppm up to 79.27 ppm. Phase III involved investigating the differences in nozzle transverse speeds and surface speeds between disk- and rod (4.5 mm in diameter)-shaped substrates for plasma HA spraying. The results of Phase III reveal that nozzle transverse speeds of 400 mm/s and titanium surface speeds of 5 rpm may be optimal for the titanium rods. Finally, Phase IV entailed using the parameters alternating from Phase III to perform HA plasma spraying on dental implants measuring 4.5 mm in diameter. An SEM morphology examination indicated that the coverage level of the HA coating was nearly uniform and the thickness was approximately 47–130 μm. This study successfully applied plasma spray technology to an HA spray for titanium surface modification. The evaluation and characterization of the resulting HA coatings reveal that the Phase IV parameters may be used for HA-coating on titanium dental implants. The coatings contained no significant phase components such as tricalcium phosphate (α-TCP, β-TCP) or tetracalcium phosphate (TTCP).

► We have developed optimum parameters for plasma sprayed HA coating on Ti surfaces.
► The crystallinity of the HA coatings in the SBF increased from 54.88 to 74.39%.
► The released Ca ion concentration increased from 44.9 up to 79.27 ppm after 28 days.
► The HA coating was nearly uniform and the thickness was approximately 47–130 μm.
► This technology could be applied to dental implant.