An in vitro Study on the Biocompatibility of Titanium Implants Made by Selective Laser Melting

Customized medical implants obtained by selective laser melting have an important applicability due the accurate architecture which promotes the osteointegration, osteoconduction, and osteoinduction. This study assessed the in vitro effect of titanium scaffolds, both pure and covered with a layer of hydroxyapatite, on mesenchymal stem cells harvested from various oral tissues. Eight titanium implants were manufactured by selective laser melting, obtaining a porosity of 63.4% and a pore size of 600 µm. Four matrices were covered with nano-hydroxyapatite. Four lines of mesenchymal stem cells isolated from the apical papilla, the dental pulp, the inter-radicular bone, and the tuberosity bone were seeded on the implants. The cells’ proliferation, viability, and differentiation into the osteoblastic lineage were assessed after 18 days, using light microscopy and fluorescence. Our results indicated that the titanium matrices did not exert cytotoxic effect. The cells seeded on titanium matrices conditioned with nano-hydroxyapatite had a slightly higher proliferation rate. The stem cells isolated from the inter-radicular bone had the most intense proliferation and differentiation towards the osteoblastic lineage showing a nodular architecture. In conclusion, the oral mesenchymal stem cells have the potential to promote and improve bone regeneration when associated with the titanium scaffolds manufactured by selective laser melting, either non-coated or coated with hydroxyapatite. These findings open new perspectives for the bone reconstruction in the oral and maxillofacial surgery field.