Additive Manufacturing Technology (Direct Metal Laser Sintering) as a Novel Approach to Fabricate Functionally Graded Titanium Implants: Preliminary Investigation of Fabrication Parameters

Purpose: This article describes the preliminary findings of the mechanical properties of functionally graded titanium with controlled distribution of porosity and a reduced Young's modulus on the basis of a computeraided design (CAD) file, using the rapid-prototyping, direct metal laser sintering (DMLS) technique. Materials and Methods: Sixty specimens of Ti-6Al-4V were created using a DMLS machine (M270) following the standard for tensile testing of metals. One group was fabricated with only 170 W of laser energy to create fully dense specimens (control group). The remaining specimens all featured an outer fully dense "skin" layer and a partially sintered porous inner "core" region. The outer "skin" of each specimen was scanned at 170 W and set at a thickness of 0.35, 1.00, or 1.50 mm for different specimen groups. The inner "core" of each specimen was scanned at a lower laser power (43 or 85 W). Results: The partially sintered core was clearly visible in all specimens, with somewhat greater porosity with the lower laser power. However, the amount of porosity in the core region was not related to the laser power alone; thinner skin layers resulted in higher porosity for the same power values in the core structure. The lowest Young's modulus achieved, 35 GPa, is close to that of bone and was achieved with a laser power of 43 W and a skin thickness of 0.35 mm, producing a core that comprised 74% of the total volume. Conclusion: Additive manufacturing technology may provide an efficient alternative way to fabricate customized dental implants based on a CAD file with a functionally graded structure that may minimize stress shielding and improve the long-term performance of dental implants.