Regenerative endodontic procedures are generally accepted by experts part 2

Regenerative endodontic procedures (REPs) have a biological basis and are histologically examined. 

 The biological basis of REPs Over the past few decades, advances in tissue engineering have fundamentally changed how we think about medical care and re-energized the field of regenerative medicine. Dental pulp tissue engineering studies are establishing a strong biological basis for the growth and promotion of REPs, which depend on three essential components: scaffolds, growth factors, and stem cells.

 a stem cell

 Different populations of adult stem cells have so far been found, and under certain circumstances, they can be made to differentiate into odontoblast-like cells, demonstrating their potential for use in REPs. These include inflammatory periapical progenitor cells (iPAPCs), bone marrow stem cells (BMSCs), periodontal ligament stem cells (PDLSCs), and dental pulp stem cells (DPSCs). 

 Some residual vital pulp tissues may still exist in the apical region of teeth even after they develop pulp necrosis, apical periodontitis, or periapical abscesses. These tissues can be used in REPs to encourage tissue regeneration. SCAPs were first identified in the apical tissue in 200628, and they have the ability to proliferate and differentiate into odontogenic cells, which is advantageous for root development. Additionally, SCAPs would be the most promising source of stem cells for REPs when combined with the location close to the apices of teeth. PDLSCs and BMSCs are additional potential stem cell sources for REPs because they may be released by evoked bleeding from apical tissue. Another significant potential source of stem cells for REPs is iPAPCs, which seem to be primarily localized in the vasculature within apical granulomatous tissues. 

 Studies have shown that over-instrumentation into the periapical tissues, both in developing and fully developed teeth, causes an increased expression of marrow stem cells (MSCs) markers in the intra-canal blood. Due to a lack of specific stem cell markers, the precise origin of these MSCs could not be determined. 

 factors that promote growth 

The dentin matrix has been thought of as a reservoir of growth factors that can be released through bacterial acid demineralization, irrigation with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA), stimulation with calcium hydroxide, and silica-calcium biomaterials like MTA and Biodentine. In addition, certain growth factors are present in the blood clot created during REPs. 

 The recruitment, proliferation, differentiation, and promotion of tissue regeneration are all thought to be significantly influenced by the growth factors derived from dentin. For instance, the promotion of cell migration and proliferation has been linked to the growth factors transforming growth factor 1 (TGF-ß1) and fibroblast growth factor 2 (FGF2). While bone morphogenetic protein (BMP) and FGF2 mediate the signaling in dentin formation, VEGF and BMP both play significant roles in cell proliferation and angiogenesis regulation. Dentin matrix protein and dentin phosphoprotein are examples of non-collagenous proteins (NCPs) that may play a role in odontogenesis. 

 In addition to autologous growth factors, exogenous growth factors have been used to enhance REPs. In an immature tooth with pulp necrosis, human recombinant platelet-derived growth factor (rPDGF)–loaded collagen scaffolds successfully induced root maturation. Additionally, a clinical trial showed that teeth with pulp necrosis could heal at the apical level and continue to develop roots when treated with injectable hydrogel scaffolds impregnated with basic fibroblast growth factor (bFGF). 

 a scaffold 

In order to direct the location of stem cells and control their proliferation, differentiation, or metabolism, a scaffold is a crucial component of tissue engineering. Additionally, it might encourage gaseous and nutrient exchanges.45 The scaffolds of REPs could be made of blood clots, autologous platelet concentrates, and synthetic biomaterials. The most frequently used scaffolds during REPs are blood clots and autologous platelet concentrates. 

 In most cases involving REPs, a blood clot has been induced as a scaffold, which is a fairly easy and basic method. Integrators on cell surfaces are able to attach to fibrous components and pick out specific cells to adsorb as a result, supplying growth factors that aid in tissue regeneration. Blood clots are difficult to obtain and lack some essential characteristics of an ideal scaffold, such as ease of delivery, superior mechanical performance, manageable biodegradation, and incorporation of growth factors. Additionally, the blood clot contains a large number of hematopoietic cells, which may release toxic intracellular enzymes into the microenvironment during cell death, endangering the survival of stem cells. Using autologous platelet concentrates such as concentrated growth factor (CGF), platelet-rich fibrin, and platelet-rich plasma (PRP) is another method for building a scaffold. The in vitro manipulation needed for these autologous scaffolds is minimal, and they are simple to make. They have a three-dimensional fibrin matrix and a lot of bioactive molecules, but they can deteriorate over time. With these autologous scaffolds, success has been found in a number of REPs cases. The clinical use, however, is not without its drawbacks, including the need for specialized equipment for the collection of intravenous blood and the inability to precisely control the types and concentration of growth factors during preparation. Their application is further hampered by their inability to control temporal degradation as well as by their lack of sufficient mechanical strength to support the coronal restoration.

 In REPs, a number of exogenous scaffolds have been clinically used, including collagen type 1, hydrogel, and collagen-hydroxyapatite. Before being inserted into immature root canals, these scaffolds are typically loaded with growth factors. Its success in clinical use has been demonstrated by the disappearance of clinical symptoms, apical radiographic radiolucency, and ongoing root development. Decellularized dental pulp has also attracted some attention in studies as a possible scaffold for pulp regeneration. A swine dental pulp that had been decellularized and implanted into canine teeth that had undergone pulpectomies was able to stimulate the growth of a vascularized pulp-like tissue that expressed odontoblastic markers, according to an in vivo study.

 

MTA APEXIFICATION case 1 apexification steps, Video