Abstract
Additive manufacturing by laser sintering is able to produce high resolution metal constructs for orthopedic and dental implants. In this study, we used a human trabecular bone template to design and manufacture Ti-6Al-4V constructs with varying porosity via laser sintering. Characterization of constructs revealed interconnected porosities ranging from 15–70% with compressive moduli of 2579–3693 MPa. These constructs with macro porosity were further surface-treated to create a desirable multi-scale micro-/nano-roughness, which has been shown to enhance the osseointegration process. Osteoblasts (MG63 cells) exhibited high viability when grown on the constructs. Proliferation (DNA) and alkaline phosphatase specific activity, an early differentiation marker, decreased as porosity increased, while osteocalcin, a late differentiation marker, as well as osteoprotegerin, vascular endothelial growth factor and bone morphogenetic proteins 2 and 4 increased with increasing porosity. Three-dimensional (3D) constructs with the highest porosity and surface modification supported the greatest osteoblast differentiation and local factor production. These results indicate that additively manufactured 3D porous constructs mimicking human trabecular bone and produced with additional surface treatment can be customized for increased osteoblast response. Increased factors for osteoblast maturation and differentiation on high porosity constructs suggest the enhanced performance of these surfaces for increasing osseointegration in vivo.
Highlights
Over two million dental implants are placed annually, and over four million hip and knee replacement surgeries are expected by the year 2030 [1, 2]
Strut thickness and surface area to volume (SA/V) ratio all increased with increasing construct porosity
Studies have pointed toward 3D porous implants as a possible solution, these surfaces have not been optimized for porosity or combined with desired surface roughness features
Summary
Over two million dental implants are placed annually, and over four million hip and knee replacement surgeries are expected by the year 2030 [1, 2]. Implant surface roughness is one factor that has been shown to successfully increase cell response in vitro and osseointegration in vivo, and micro-rough surfaces are currently used as the industry standard in dental and many bone-interfacing orthopaedic implants [8, 9]. By altering only the surface microtopography and without exogenous factors in media, osteoblast differentiation can be increased on titanium surfaces [12]. This may be due in part to the protein-material interaction at the surface, which affects downstream cell response. Changes in the cytoskeleton, including integrin expression and signaling, have been implicated in this effect [13, 14]
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