Laser-assisted manufacturing of 45S5 Bioglass-coated zirconia structured surfaces targeting medical implants: adhesive, wettability, mechanical, and bioactivity evaluation

In this study, a new design for implants surface functionalization through the manufacture of 45S5 Bioglass-coated zirconia structured surfaces by means of hybrid laser technique was explored to ensure no detachment of the 45S5 Bioglass coating from the implant surface upon implantation. The functionalization process started with the manufacture of green zirconia compacts by cold pressing technique, followed by surface texturing using a ns-Nd:YAG laser and subsequent sintering using a high-temperature furnace. Afterwards, a 45S5 Bioglass coating of the textured surfaces was performed by dip-coating technique, which was then sintered using a CO2 laser. Targeting implants applications, the 45S5 Bioglass-coated zirconia structured surfaces were assessed regarding morphology, 45S5 Bioglass bioactivity preservation, surface wettability, friction performance, and mechanical resistance of zirconia. The morphology of functionalized surfaces was evaluated through the SEM analysis, and it was observed that a densely sintered 45S5 Bioglass coating outlining the underlying micro-texture profile was obtained combining subtractive and additive laser manufacturing strategies. EDS and XRD analyses were performed to look for possible 45S5 Bioglass chemical changes, being verified a Ca/P ratio (4.9) very closed to the one reported for non-degraded 45S5 Bioglass (5) and the maintenance of 45S5 Bioglass crystallinity, demonstrating that the coating material bioactivity was preserved after laser sintering. These promising results were also corroborated by wettability tests, which revealed a significant increase (up to similar to 30%) on the wettability of 45S5 Bioglass-rich structured zirconia surfaces as compared to as-sintered and laser textured zirconia surfaces. Regarding friction performance, it was experimentally demonstrated that the 45S5 Bioglass coating was able to keep its integrity during the sliding tests against bone, with no bioactive material being transferred to the bone. The mechanical resistance of zirconia was assessed by biaxial flexural tests, which revealed a flexural strength value (520 +/- 65 MPa) that complies with the requirements of the ISO 13356:2008 standard. The results showed that the synergistic effect of combined physical and chemical changes performed on the zirconia surface together with the advanced laser texturing/sintering methods here explored seems to be a promising approach for producing zirconia-based implants with enhanced bioactivity required for an effective osseointegration.

Automated summary

This study explored a new design for implants surface functionalization through the manufacture of 45S5 Bioglass-coated zirconia structured surfaces using a hybrid laser technique. The results showed promising outcomes in terms of morphology, bioactivity preservation, surface wettability, friction performance, and mechanical resistance of zirconia. The synergistic effect of physical and chemical changes on the zirconia surface with advanced laser methods seems to be a promising approach for producing implants with enhanced bioactivity.