Laser surface modification of hydroxyapatite coated Ti alloy

Plasma spray hydroxyapatite(HA) coated titanium alloy specimens were laser treated with a CW CO₂ laser and a pulsatile Nd-Yag laser. Surface morphology was studied with scanning electron microscope(SEM) and optical microscope. The Ca/P ratio and distributions were semiquantitatively analyzed with x-ray energy dispersive microanalyzer (EDX). X-ray diffraction pattern of laser treated specimen was obtained using a x-ray diffractometer(XRD) with CuKα radiation. Cytotoxicity was examined in a CO₂ incubator. The interfacial shear modulus and shear strength was measured with a mechanical tester. Laser treatment on the HA plasma spray coated titanium alloy could change surface structure into glassy melted pool, dendritic structure and flake like structure. The distribution of Ca and P in laser melted zone (LMZ) became uniform. The Ca/P ratio decreased from 1.67 to 1.4 for CO₂ laser treatment and to 1.0 for Nd-Yag laser treatment. There was no cytotoxicological difference between laser treated specimen and plasma spray coated one. Laser treated specimen shown higher interfacial shear modulus compare to the HA coated specimen. These results show that the newly formed LMZ can improve interfacial bond strength between HA and matrix without cytotoxicological deficit.