# In Vitro Effect of Putty Calcium Silicate Materials on Human Periodantal Ligament Stem Cells
## 4 Discussion  
The appearance of different materials to treat dental perforation or to perform apical surgery facilitates our choice of options. It is necessary to know the properties of the materials to determine which one is better for each type of problem [20]. In our study, we compared the cytocompatibility and bioactivity potential of these two new bioactive materials, BCR and TFB, with PDLSCs. We chose this cell type because, in the indications of these materials, PDLSCs have contact with the periodontal ligament which are at the root-end cavity when periapical surgery is done or when iatrogenic perforation is repaired it is next to the periodontal ligament [10; 21]. Other studies have used dental pulp stem cells with direct pulp capping materials [22], or osteoblast cells when they have also studied endodontic cements [23; 24]. Therefore, the clinical situation is crucial for the choice of cell line. Figure 7: Mineralization capacity of root repair cements. Alizarin Red staining to evaluate the bioactivity potential of BCR and TFB. Differences observed are shown as \({}^{**}p<0.01\) and \({}^{***}p<0.001\). We used the MTT test due to its ease of performing and its accuracy [25]. In addition, the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay is commonly accepted for in vitro cytotoxic studies. TFB and BCR showed similar results in terms of cell viability as compared with a control group. In line with this work, previous reports have described similar results, also using the MTT test with TotalFill BC sealer, which has an almost identical composition, except it changes consistency [25; 26]. [PERSON] et al. [27] also reported that BCR is a biocompatible material that induces mineralization in vivo. Unsurprisingly, our results evidenced that both cements were safe and did not promote adverse effects on hPDLSCs. Cellular migration is essential for an apical healing after a retrograde root filling, or after repair of a fuccal iatrogenic perforation because it helps in calcified tissue formation [28]. In our study, both materials allow cell migration; this may be due to calcium ions since they favor migration [29]. The SEM-EDX assay showed a high amount of Ca\({}^{2+}\) ions in both cements, especially in TFB, which could help increase the pH of the area and have a positive influence on healing [30]. Our results are consistent with other studies that have shown the migration capacity of the root repair materials. For example, iRoot FS (Innovative Bioceramix, Vancouver, BC, Canada) showed cell migration rates higher than ProRootMTA (Dentsply, Tulsa, OK, USA) [28], or Biodentine (Septodont, St Maur des Fosses, France) has been evidenced by anti-inflammatory properties and favored fibroblast migration to the injury site [31]. Nevertheless, the detailed mechanism of how premixed and putty calcium silicate materials favors cell migration is unknown. The connection between cells and biomaterial is essential for cell differentiation, and cell attachment has been associated with actin stress fibers [32; 33]. Both premixed material's surfaces favored cell adhesion. In our study, hPDLSCs displayed a well interconnected characteristic fibrobl morphology. This result is congruent with another report that showed that calcium silicate materials facilitated cell attachment and promoted cell proliferation [34]. Furthermore, a biological seal on the root repair materials can be achieved by the interactions between materials and hPDLSCs. Bioactivity potential is defined as the cellular effects induced by ions or active substances from biomaterials [35]. Our results showed overexpression of CEMP-1, CAP, and Runx2 with BCR on day seven. These genes are involved in the osteo- and cementogenic differentiation of stem cells, and consequently in apical healing. CEMP-1 is related to migration, proliferation, and differentiation of periodontal ligament cells into cementoblast-like cells. CAP promotes maturation and deposition of the mineralized extracellular matrix.