**5.1 Additive manufacturing**

Some studies have used conventional methods for producing scaffolds. However, these methods have no adequate control over pore size and design or interconnectivity [8, 85]. In order to address these problems, since the mid-1980s [86], a new manufacturing type of technology called AM has emerged. Its potential is enormous and overcomes the capabilities of the conventional technologies to produce scaffolds with a complex architecture and with the intention to achieve an appropriate mechanical response to the desired application [36].

Nowadays there are several approaches to AM for various applications. The main approaches are fused filament fabrication (FFF), three-dimensional printing (3DP), stereolithography (SLA), and selective laser sintering (SLS). Each process goes through several steps: (i) development of the 3D model through computeraided design (CAD); (ii) the files are stored in standard triangular language (STL) format, which is a CAD file format that supports 3D printing and computer-aided manufacturing (CAM); and (iii) these files are inserted into the input devices to create 3D models in a layer-by-layer process [36]. In addition, there are still two processes where it uses the same principles of layer manufacturing: selective laser melting (SLM) [87–90] and electron beam melting (EBM) [91–93]. Both are used to produce metal scaffolds, although SLM can also process polymers and ceramics [3, 94, 95].

FFF, **Figure 1**, or melt-extrusion is an extrusion-based process and is the simplest 3D printing method (see **Table 3**) [36, 96]. Fine thermoplastic polymers in the form of filaments or granules are cast and extruded through a nozzle that allows

**Figure 1.** *Fused Filament Fabrication (FFF) process.*


**169**

**Figure 2.**

*from [106]).*

*Comprehensive Review on Full Bone Regeneration through 3D Printing Approaches*

ing of the same layer, layer thickness, and deposition angle [96].

pore size, which are the deposition velocity and the rotational velocity.

flow in a horizontal and vertical plane (XY plane) [36]. To extrude it is necessary to have heating of the material, which causes degradation. However, the disadvantages of this technique can be overcome. The most suitable and desired mechanical properties can be achieved for the desired purpose with the combination of biomaterials. With this technique, it is already possible to extrude some bioceramics, such

It is critical that the first layer is maintained at a temperature slightly below its set point to ensure successful adhesion between the layers. The 3D structure is determined by several factors, such as nozzle diameter, deposition rate, path spac-

In the FFF technique, it is possible to control layer thickness and print orientation. The structural geometry of scaffolds is determined by the position and orientation of the filaments, which provide various pore shapes such as triangular, parallelogram, hexagonal, and also nonuniform shapes [100]. In this technique, there are two factors that affect the filament size, and consequently the

It is necessary that the scaffolds in bone regeneration be biocompatible, biodegradable, osteoinductive (raising and cell maturation), and osteoconductive (provide a platform for cell growth) [39]. Scaffolds for bone regeneration should meet several specific criteria, such as filling any bone defect, ensuring pore interconnectivity, and having a pore architecture in order to promote bone formation and facilitate the exchange of oxygen bone growth [101–103]. The design of the scaffold can influence both the mechanical properties and cellular behavior [100,

A satisfactory bone growth leads to certain requirements. Porosity should be above 50% and pore size between 50 and 400 μm. It is difficult to achieve a "perfect" scaffold for bone regeneration due to pore design and size and a porosity distribution that mimics the native tissue [107, 108]. In the literature, there are no quantitative criteria that specify porosity or pore size or topology for bone regeneration. Porous scaffolds ranging in size from 50 to 500 μm are known to promote cell migration and vascularization, while micropores and nanopores control interaction

*Scaffold requirements in terms of response (left) and what should be taken into account (right) (adapted* 

with proteins and ion exchange with extracellular fluids [19, 109].

*DOI: http://dx.doi.org/10.5772/intechopen.90864*

as HAp [97–99].

**5.2 Temporary implants**

104, 105] as highlighted in **Figure 2**.

#### **Table 3.**

*Advantages and disadvantages of the fused filament fabrication process.*

#### *Comprehensive Review on Full Bone Regeneration through 3D Printing Approaches DOI: http://dx.doi.org/10.5772/intechopen.90864*

flow in a horizontal and vertical plane (XY plane) [36]. To extrude it is necessary to have heating of the material, which causes degradation. However, the disadvantages of this technique can be overcome. The most suitable and desired mechanical properties can be achieved for the desired purpose with the combination of biomaterials. With this technique, it is already possible to extrude some bioceramics, such as HAp [97–99].

It is critical that the first layer is maintained at a temperature slightly below its set point to ensure successful adhesion between the layers. The 3D structure is determined by several factors, such as nozzle diameter, deposition rate, path spacing of the same layer, layer thickness, and deposition angle [96].

In the FFF technique, it is possible to control layer thickness and print orientation. The structural geometry of scaffolds is determined by the position and orientation of the filaments, which provide various pore shapes such as triangular, parallelogram, hexagonal, and also nonuniform shapes [100]. In this technique, there are two factors that affect the filament size, and consequently the pore size, which are the deposition velocity and the rotational velocity.
