# A Molecular View on Biomaterials and Dental Stem Cells Interactions: Literature Review
## 2 Dental Stem Cells  
Mesenchymal stem cells (MSCs) are a group of cells capable of self-renewal and function as a repair system for damaged tissues. When a stem cell divides, each cell has the potential to remain a stem cell or to become another type of cell with a more specialized function. Thus, stem cells have two characteristics: the ability to self-renew and differentiate in any cell lineage (e.g., osteogenic, chondrogenic, adipogenic, myogenic, and neurogenic) comparable to those established for bone marrow-derived MSCs. They can be classified according to their origin in embryonic stem cells, adult stem cells (tissue-specific), and induced pluripotent cells (iPS) [3]. All of them are attractive for their use in the regeneration of damaged tissues; however, their clinical application is still limited due to the transplanted cells' low survival and differentiation potential. For a thorough understanding of the origin and biology of different stem cells, the reader is referred to excellent reviews on this subject [4; 5].  
Oral cavity tissues are rich sources of adult stem cells. These cells are called dental tissue-derived mesenchymal stem cells (DT-MSCs), and the method of obtaining them is relatively easy in dental tissues and, even better, they are a source of autologous stem cells [1; 6]. Likewise, they present a high proliferation, ability to differentiate into multiple cell types, and the expression of positive and embryonic markers of MSCs (i.e., OCT4, Nanog, SOX2, and KLF4), which makes them more attractive for their application in regenerative medicine [1; 7; 8; 9]. Different types of DT-MSCs have been identified, such as dental pulp stem cells (DPSCs), exfoliated deciduous tooth stem cells (SHEDs), periodontal ligament stem cells (PDLSCs), dental follicle stem cells (DFSCs), and stem cells from the apical papilla (SCAP) (Figure 1) [1]. Although these types of cells have been shown to have stem, clonogenicity, and self-renewal characteristics, their differentiation capacity varies according to the origin of the cells. Some authors have pointed out that this behavior could be due to: (1) the heterogeneity of DT-MSCs and (2) the microenvironment of stem cells in dental tissues, for example, teeth in pre-eruptive formation (dental follicle and apical papilla) versus erupted teeth (dental pulp or periodontal ligament) [3; 10; 11]. Thus, one of the challenges for the clinical application of DT-MSCs is to mimic the appropriate microenvironment so that cells can proliferate or differentiate properly [3]; to achieve this, cells need extracellular matrix (ECM) components (Figure 1). Numerous studies have focused on developing artificial ECM microenvironments that are favorable for DT-MSC regeneration activities. The combination of DT-MSCs with biomaterials is one of the key procedures for developing autologous therapeutics in the regeneration of dental and nondental tissues. Next, the relevant aspects of biomaterials will be reviewed, as well as the most important cellular and molecular mechanisms involved in the regenerative process of stem cells of dental origin.