Root Analog 3D-printed Dental Implants: The Nano-level Challenges (808)

Dental implants are widely recognized as common replacements for natural teeth. The convergence of Additive Manufacturing (AM) and direct metal laser sintering (DMLS) has enabled the creation of personalized implants with a favorable combination of mechanical and biological properties. This goes beyond the traditional use of commercially pure titanium (cpTi) or its Ti–6Al–4V alloy. The AM method, also known as 3D printing, constructs structures by layering materials, eliminating the need for complex post-processing steps.
Over the past decade, extensive research has delved into the chemical and mechanical characteristics of 3D printed titanium structures. At the same time, various in vitro studies have investigated cell responses to the surfaces of additively manufactured implants, including the behavior of human mesenchymal stem cells and osteoblasts. These studies encompass cell adhesion, proliferation, and the development of osteogenesis. Furthermore, numerous animal and human histologic/histomorphometric studies have documented adhesion and bone responses following the insertion of titanium devices.
However, the manufacturing process introduces multiple factors that lead to uncertainties in consistently achieving high-quality surfaces, precise dimensions, and an optimal balance between the mechanical and biological properties of the final product.
The successful osseointegration and biocompatibility of the root analogue implant (RAI) hinge primarily on the chemical surface composition of the titanium alloy used. After the completion of the Direct Metal Laser Sintering (DMLS) process, the leftover titanium alloy powder is recycled for subsequent 3D printing phases. This recycled powder, having undergone the manufacturing process, may show disparities in surface composition compared to the sealed titanium alloy powder sourced directly from the manufacturer. The interaction between the RAI alloy and bone tissue depends on the relative makeup of the alloy constituents. Notably, studies suggest that increasing the Al and/or V content in the surface composition enhances the adhesion of osteoblast-like cells through fibronectin-mediated mechanisms.
Titanium naturally forms a biocompatible surface oxide layer primarily composed of TiO2, which facilitates interactions with biological elements when the implant is inserted. This layer, known as the passivation layer, plays a crucial role in the excellent osseointegration of titanium implants because it forms immediately on the surface in air or aqueous environments, potentially undergoing calcification. The present study aims to examine the processing's impact on the surface oxide layer in both types of powder. By comparing the powders (in their original and recycled states) and 3D printed RAI samples at various depths, the thickness of the passivation layer can be determined. The chemical surface composition of these distinct alloys, along with the thickness of the passivation layer, forms the basis for evaluating the cytotoxic potential of future manufactured RAI designs.