Effect of surface pre-treatment with Er: YAG laser on hydroxyapatite coating adhesion and mechanical properties of titanium alloy discs

The use of hydroxyapatite (HAp) as a surface coating enhances the properties of titanium (Ti) by ensuring bioactivity and inducing bone apposition. The coating’s limited adhesion to metal surfaces is a challenge, so improving it prevents delamination, inflammatory responses and mechanical failure of implants. The aim of this in vitro study was to evaluate the influence of Erbium-Doped Yttrium Aluminum Garnet (Er: YAG) laser irradiation as a pre-treatment on Ti-6Al-4 V surfaces on the adhesion of HAp coatings. Two groups of Ti-6Al-4 V discs (G1: machined + HAp coated and G2: laser irradiated + HAp coated) were evaluated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and the crystalline phases of the coating by X-ray Diffraction (XRD). The physical properties were analyzed by microhardness, surface roughness and adhesion according to ASTM-D3359. Microhardness results were subjected to the t-test and surface roughness to the Mann-Whitney test. A 5% significance level was adopted. The characterization analyses were evaluated qualitatively. Laser treatment increased hardness (p = 0.013) and surface roughness (p = 0.002), while the untreated machined surface showed better coating adhesion. XRD, SEM and EDS analysis confirmed the formation of the HAp coating. Using the Er: YAG laser at the parameters determined in this study, no better adhesion of the coating was observed. However, laser irradiation provided greater hardness and roughness compared to films deposited on machined surfaces.