# Magnetism in Dentistry: Review and Future Perspectives
## 2 Tissue Engineering
### Scaffold Design Strategies  
Among all the scaffold design strategies, additive manufacturing methodologies have emerged as powerful tools for obtaining polymeric and/or micro- nano-composite structures with an appropriate and controlled morphology and porosity. The chemical structure of the scaffold material and its internal architecture (filaments and walls diameter, and porosity) control and modulate the biological performances of the cells [21]. Cell behaviour over time is strictly connected to pores morphology and dimensions. Furthermore, a fully interconnected porosity is crucial for the ingrowth of surrounding tissues [22]. An interconnected and open porosity enhances mass transport properties and the elimination of waste generated by cellular metabolism [23]. Furthermore, the enzymatical or hydrolytic degradation of polymers represents an added value. Natural polymers such as chitosan, alginate, collagen, and gelatin are frequently used as bioinks and subject to enzymatic degradation, due to the presence of microorganisms in the biological environment [24]. The availability and concentration of respective enzymes is strictly connected with the rate of enzymatic degradation. Hydrolytic degradation of synthetic polymers is related to the splitting of hydrolytically sensitive bonds, resulting in bulk or surface erosion, which is crucial for the determination of the best choice for different applications [25]. Surface erosion implies the preservation of mechanical integrity, also enhancing bone ingrowth, and ensuring gradually scaffold substitution by new bone tissue [26]. Generally, polymers can be processed in order to obtain porous structures which are capable of facilitating the transport of growth factors, nutrients, anabolites and catabolites, and controllable degradation [27]. Furthermore, composite materials may properly be adopted because of their versatility resulting from the combination of organic and inorganic phases. Recent studies on this subject have highlighted the innovation of targeted and scaffold-assisted regeneration of enamel, dentin, and cement [28]. Biocompatible, biodegradable, porous, and without toxic metabolites materials adopted as scaffold fabrication materials for dental regeneration approaches must possess other peculiar characteristics suitable for the specific environment and that make them applicable to the oral cavity: pH, temperature, microorganisms' interaction, and mastication forces. In order to achieve these properties, most scaffolds mimic the structure of the natural ECM, thus avoiding inflammatory responses. In this context, the development of smart immunomodulatory biomaterials which prevent foreign body reaction on the patients and regulate the immunological microenvironments to ensure cell survival is crucial [29; 30]. Biomimetic porous PLGA microspheres coupled with peptides have been prepared to mimic natural tissues in terms of chemical composition and structure and adopted as biomimetic and bionic smart scaffolds [31]. MSCs, bone marrow, and macrophages behaviour over time has been analysed in conjunction with amino-functionalized bioactive glass scaffold [32]. \(\beta\)-tricalcium phosphate coatings on Mg scaffolds have been also analysed to modulate its harmful osteoin-munomodulatory properties [33]. Shape-memory porous smart scaffolds for bone repair defects have been also proposed. In particular, bone morphogenetic protein2-loaded shape-memory porous nanocomposite scaffolds have been developed adopting nanoparticles of poly(\(\varepsilon\)-caprolactone) and hydroxyapatite with shape-memory recovery which were chemically crosslinked [34]. Furthermore, 3D flexible piezoelectric poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) fibrous scaffolds were obtained and adopted for MSCs differentiation and novel tissue formation [35], whilst an electrospun PVDF-TrFE fibre scaffold containing zinc oxide nanoparticles was highlighted to promote human MSCs performances in terms of adhesion and proliferation and also to enhance the blood vessel formation [35].