Titanium surface modified by hydroxyapatite coating for dental implants

Abstract

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 120μm), are divided into four stages. An immersion test for the HA coatings in a simulated body fluid (SBF) was performed after HA coating. After 28days, 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 44.9ppm up to 79.27ppm. Phase III involved investigating the differences in nozzle transverse speeds and surface speeds between disk- and rod (4.5mm in diameter)-shaped substrates for plasma HA spraying. The results of Phase III reveal that nozzle transverse speeds of 400mm/s and titanium surface speeds of 5rpm 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 4.5mm in diameter. An SEM morphology examination indicated that the coverage level of the HA coating was nearly uniform and the thickness was approximately 47–130μm. 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).