Main 3D Manufacturing Techniques for Customized Bone Substitutes. A Systematic Review

Clinicians should be aware of the main methods and materials to face the challenge of bone shortage by manufacturing customized grafts, in order to repair defects. This study aims to carry out a bibliographic review of the existing methods to manufacture customized bone scaffolds through 3D technology and to identify their current situation based on the published papers. A literature search was carried out using “3D scaffold”, “bone regeneration”, “robocasting” and “3D printing” as descriptors. This search strategy was performed on PubMed (MEDLINE), Scopus and Cochrane Library, but also by hand search in relevant journals and throughout the selected papers. All the papers focusing on techniques for manufacturing customized bone scaffolds were reviewed. The 62 articles identified described 14 techniques (4 subtraction + 10 addition techniques). Scaffold fabrication techniques can be also be classified according to the time at which they are developed, into Conventional techniques and Solid Freeform Fabrication techniques. The conventional techniques are unable to control the architecture of the pore and the pore interconnection. However, current Solid Freeform Fabrication techniques allow individualizing and generating complex geometries of porosity. To conclude, currently SLA (Stereolithography), Robocasting and FDM (Fused deposition modeling) are promising options in customized bone regeneration.

Introduction to Additive Manufacturing

Additive manufacturing (AM) is also referred to as 3D printing, rapid prototyping, solid freeform fabrication, rapid manufacturing, desktop manufacturing, direct digital manufacturing, layered manufacturing, generative manufacturing, layered manufacturing, solid free-form fabrication, rapid prototype, tool-less model making, etc. It is emerging as an important manufacturing technology. It is the process of building up of layer-by-layer by depositing a material to make a component using the digital 3D model data. The main advantages of AM are mass customization, minimisation of waste, freedom of designing complex structures, and ability to print large structures. AM is broadly applicable to all classes of materials including metals, ceramics, polymers, composites, and biological systems. The AM methods used for producing complex geometrical shapes are classified based either on energy source (laser, electron beam) used or the material feed stock (powder feed, wire feed).

Three-dimensional printing with biomaterials in craniofacial and dental tissue engineering

With the development of technology, tissue engineering (TE) has been widely applied in the medical field. In recent years, due to its accuracy and the demands of solid freeform fabrication in TE, three-dimensional printing, also known as additive manufacturing (AM), has been applied for biological scaffold fabrication in craniofacial and dental regeneration. In this review, we have compared several types of AM techniques and summarized their advantages and limitations. The range of printable materials used in craniofacial and dental tissue includes all the biomaterials. Thus, basic and clinical studies were discussed in this review to present the application of AM techniques in craniofacial and dental tissue and their advances during these years, which might provide information for further AM studies in craniofacial and dental TE.

Research on Curved Layer Fused Deposition Modeling (CLFDM) With Variable Extruded Filament (VEF)

Fused Deposition Modeling (FDM), an Additive Manufacturing (AM) technique, is widely used due to its low-cost and open source. Geometry accuracy and strength performance of the printed parts are closely related to inter-layer bonding between adjacent layers and inter-road bonding in the layer. Because of the limit of layer-based AM, the longitudinal tensile strength of the filaments is much higher than the bonding strength between adjacent filaments, which brings anisotropy of the printed part. While CLFDM is devoted to solve this problem and obtain better geometry accuracy and meanwhile decrease build time by virtue of high continuity of filament, reduced stair-step effect, and lesser number of layers, especially when manufacturing thin and curved parts (shells). However, to the best of our knowledge in the aspects of process modeling of CLFDM, available researches focus mainly on simple curved layer, instead of more intricate ones possessing tiny features, which are more common in manufacturing. Therefore, to realize Solid Freeform Fabrication (SFF), this paper researches CLFDM with VEF (simultaneously changing the direction and the dimension of extruded filament according to manufacturing demand of the curved layer), which would be a fundamental study and a foundation for Advanced Design for Additive Manufacturing (ADFAM), slicing and path planning (extruder path generation) in 3D space. To realize slicing and printing with homogeneous and inhomogeneous extruded filament between consecutive layers and within the layer (flat or curved), models of flat layer FDM and CLFDM with VEF are respectively established. Then, the relationships among key process parameters are analyzed. Finally, graphical simulation of the proposed strategy based on a vase is provided to verify its effectiveness and advantages from a theoretical point of view. In general, variable direction of extruded filament along tangential directions of part surface imparts smoother surfaces, instead of rough exterior appearance resulting from stair-step effects. And variable dimension of extruded filament maximizes material extruded to increase build speed wherever allowed and minimizes deposition size for resolution whenever needed, resulting in curved layer surfaces with uneven layer thickness and having tiny features.