In vivo biocompatibility evaluation of 3D-printed nickel–titanium fabricated by selective laser melting

Abstract

Nickel–titanium (NiTi) belongs to the group of shape-memory alloys (SMAs), which are characterized by flexibility and reversible deformability. Advanced techniques in 3D printing by selective laser-melting (SLM) process allow the manufacturing of complex patient-specific implants from SMAs. Osteosynthesis materials made of NiTi could be used for minimally invasive surgical approaches in oral- and maxillofacial surgery. However, the in vivo biocompatibility has not yet been fully investigated, especially in load-sharing and load-bearing implants. The aim of this study was to evaluate the in vivo biocompatibility of SLM-produced NiTi for intraosseous and subperiosteal applications. Test specimens were implanted into the frontonasal bone of ten miniature pigs. To assess peri-implant bone metabolism, fluorescent dye was administered after 2, 4, 6, 10, 12, and 14 weeks intraperitoneally. Specimens and the surrounding tissues were harvested after 8 and 16 weeks for histological analysis. While the NiTi implants presented a higher bone-to-implant contact ratio (BIC) after 8 than after 16 weeks (43.3 vs. 40.3%), the titanium implants had a significantly higher BIC after 16 weeks (33.6 vs. 67.7%). Histologically, no signs of peri-implant inflammation or foreign-body reaction were detectable. With respect to this preliminary study design, 3D-printed NiTi shows sufficient biocompatibility for intraosseous and subperiosteal implant placement.

3D printing metal implants in orthopedic surgery: Methods, applications and future prospects

“…Although the Young's modulus of Ni–Ti is higher than that of natural bone, it can be reduced to 11–20.5 ​GPa for porous NiTi implants using 3D printing techniques [ 116 ]. The 3D printing porous Ni–Ti skeletal fixation device provides adequate fixation stiffness over a 6–9 month healing period and has the flexibility to return to normal stress distribution after the bone is fully remodeled [ 117 ]. Based on the properties of SMA, Ni–Ti alloys are used in orthopedic implants such as spinal implants, intramedullary nails, scoliosis correction devices, and spinal spacers [ 68 , 69 ].…”

Nitinol: From historical milestones to functional properties and biomedical applications

“…102 Figure 10 shows the SLM procedure of finished Nitinol SLM structure from CAD model to final structure. 103 In a recent study by Naujokat et al, 104 the in vivo biocompatibility of SLM-produced Nitinol for intraosseous and subperiosteal applications was investigated. The 3D-printed Nitinol samples were implanted into the frontonasal bone of pigs.…”

The role of NiTi shape memory alloys in quality of life improvement through medical advancements: A comprehensive review

“…48,115,116,[118][119][120][121]125,164,165 Maffia et al 166 have investigated the application of SLM for the fabrication of customizable NiTi stents, assessing it to be able to fabricate NiTi open-cell peripheral stents of good geometrical fidelity and high density. Recently, the vivo biocompatibility of load-bearing and load-sharing NiTi implants fabricated through SLM was investigated by Naujokat et al, 167 producing promising results. AM 162 (c) prosthetic hand, 162 (d) nitinol smart prosthesis of middle ear before (left) and after (right) activation, 163 (e) wearable exoskeleton for elbow, 162 and (f) dynamic KAFO.…”

“…48,115,116,118–121,125,164,165 Maffia et al 166 have investigated the application of SLM for the fabrication of customizable NiTi stents, assessing it to be able to fabricate NiTi open-cell peripheral stents of good geometrical fidelity and high density. Recently, the vivo biocompatibility of load-bearing and load-sharing NiTi implants fabricated through SLM was investigated by Naujokat et al, 167 producing promising results. AM techniques provide for a wide range of customization options for vascular stent design, allowing for the development of stents suitable for vessel of different proximal and distal diameters, cross-branch structures, as well as new shapes & sizes not possible with conventional methods.…”