# Endodontic Regenerative Procedures in Necrotic Adult Teeth
## 3 Results
The conventional and simplest technique to achieve revascularization is by stimulating bleeding 2 mm under the apical with a manual file [57]. Previous studies have failed to achieve a consensus regarding the optimal apical diameter that better allows revascularization [14; 18; 29; 60], although success has been reported in diameters between 0.3 to 1 mm [14]. One of the trials included in this review compares rate success through REP in mature teeth with different apical preparations (0.3 and 0.5 mm), concluding that the size of the apical diameter does not influence treatment success [33]. Therefore, although more studies are needed, it seems that revascularization can take place in teeth with apical diameters of 0.3 mm. Regardless the apical foramen diameter, revascularization potential may be compromised due to patient's age. Through their trials, [PERSON] [34] and [PERSON] [33] obtained successful results by stimulating bleeding, and most of the clinicians through case reports also performed this technique successfully. Those who did not achieve bleeding or chose platelet-rich concentrates opted for PRF, PRP, L-PRF, or the combination of both techniques. If a REP failure occurs, other conservative approaches can be considered, whether that be a second attempt of the same technique, as the REP-retreatment successfully performed by [PERSON] in 2020 [44], a conventional root canal treatment in mature teeth, or the placement of a mineral trioxide aggregate apical plug in open apexes. If the conservative treatment options are dismissed or rejected by the patient, an extraction and placement of a dental implant can be considered. In young patients, implant placement should be postponed until adulthood [61], managing the tooth's loss through a resin-bonded fixed partial denture [62]. Time-dependence relationship of pulp regeneration is one of the main challenges posed by REPs. To determine how these treatments are influenced by age, conducting randomized clinical trials in narrow age groups would be required. For example, [PERSON] in 2016 states that REPs can be applied in patients aged 9 to 18 years, concluding that the younger the age, the better the prognosis [29]. When an unsuccessful REP occurs in an adult patient, the cause may lie on the lower potential of its stem cells, so it is necessary to determine when it would be better to perform a cell transplant. In this review, two authors successfully performed cell transplantations using umbilical cord mesenchymal stem cells (UC-MSCs) encapsulated in platelet-poor plasma [35] and stem cells from exfoliated deciduous human teeth (SHED) [39]. Since the immunogenicity of mesenchymal stem cells is low, cell banks may become a real alternative [63]. Although these techniques are not currently available to all clinicians, with a view to the future, [PERSON] estimates that cell banks will provide stem cells cryopreserved and safely transported to the dental clinic for REP [64]. One of the main unknowns is how to determine the best combination of irrigants and intracanal medication to achieve complete disinfection of the canal system while promoting,or at least not harming, tissue regeneration. To this point, EDTA should be used in all regenerative procedures [21], as it appears to enhance the liberation of dentin growth factors [59; 65; 66; 67], which are essential as biological inductors and remain entrapped in the dentinal matrix as reservoir [68]. Besides, EDTA partially reverses the deleterious effects of NaOCl and promotes SCAP survival and differentiation [59]. The AAE recommends an irrigation with 1.5% NaOCl (20 mL/channel, 5 min) during the first session, followed by saline or EDTA (20 mL/channel, 5 min). In adult teeth, the irrigation protocol favored by most authors in the first session is irrigation with NaOCl. Regarding the concentration, the disagreement is notorious, although most clinicians lean towards 1.5%. During the second session, there is great disagreement regarding the irrigation protocol, although most clinicians apply 17% EDTA.