## 2 Nanomaterials in Endodontics
### Regenerative Endodontic Treatment at Nanoscale  
Regenerative endodontic treatment (RET) is an advanced field of dentistry that aims to restore the living pulp in the tooth, which allows it to continue to develop and function. This procedure is particularly important for young patients whose teeth have not yet reached full maturity [172, 173]. Regenerative endodontics focuses on the use of advanced biological methods and innovative materials that are designed to stimulate the regenerative processes occurring inside the tooth. It is based on three key elements of regenerative engineering: stem cells (Table 2), bioactive molecules, and scaffolds. The stem cells used in RET can come from various sources, such as dental pulp, alveolar bone or peripheral blood. They are pluripotent cells, meaning they have the ability to differentiate into various cell types, including dental pulp cells [174]. Bioactive molecules, such as growth factors (e.g., BMP, TGF-\(\beta\), FGF), are essential to stimulate stem cell activity. They support the processesof cell proliferation, differentiation and migration. Other bioactive mediators, such as bone morphogenetic proteins, act synergistically with growth factors, promoting the complex development and regeneration of dental tissues [175]. Scaffolds, on the other hand, are biocompatible structures that provide a spatial architecture for stem cells, enabling them to settle, proliferate and differentiate. They provide mechanical support and an appropriate microenvironment for regenerating tissues. They can be made of various materials, such as collagen, hydrogels, synthetic polymers or natural biopolymers--biodegradable and bioactive [176]. The most commonly used method for producing nanofibers is electrospinningning. This process involves creating fibers by drawing out a polymer solution using an electric field. The resulting fibers have diameters in the nanometer range and can be formed into three-dimensional structures that mimic the natural extracellular matrix (ECM), creating a suitable microenvironment for stem cell growth and differentiation. They are made from a variety of materials, including synthetic and natural polymers, which allows their properties to be tailored to specific regenerative needs [179]. Remaining on the subject of regenerative endodontics, it is worth mentioning resolvins, especially RvE1; these are natural lipids derived from omega-3 fatty acids, which play a key role in anti-inflammatory and regenerative processes. Resolvins support tissue repair processes by stimulating cells to proliferate and differentiate, as well as by inhibiting apoptotic processes (cell death) [180]. In the context of regenerative endodontics, research on the use of resolvins focuses on their potential in the regeneration of infected and damaged dental pulp. Experiments conducted on both laboratory models and animals have shown that resolvin RvE1 can effectively reduce inflammation and support regenerative processes in dental pulp. In clinical cases of infected and damaged pulp, the use of RvE1 shows promising results in terms of pain reduction, the reduction of swelling and the regeneration of damaged tissues [181]. Melanocortin peptides, in particular \(\alpha\)-MSH (\(\alpha\)-melanotropin, \(\alpha\)-melanocyte-stimulating hormone), have significant potential in endodontic regeneration due to their anti-inflammatory, antioxidant and cell proliferation-stimulating properties. \(\alpha\)-MSH exhibits strong anti-inflammatory effects by inhibiting the production of pro-inflammatory cytokines and chemokines and reducing the infiltration of inflammatory cells into the site of damage [117]. Studies on the use of these peptides in dental pulp treatment indicate their effectiveness in reducing inflammation and supporting tissue regeneration. Innovative approaches, such as the use of nanostructured scaffolds functionalized with \(\alpha\)-MSH, may contribute to the further development of regenerative therapies in dentistry [182].