## 3 Discussion
However, the cytotoxic effect of these chemicals can have a detrimental effect on the survival of the stem cells [30], which play a significant role in RET. In order to overcome this issue, gentle but effective chemical irrigation is needed [9]. NaOCl forms chloramine molecules when it reacts with organic tissue [31]. In the case of extrusion into the periapical space, this can cause necrosis of the tissues [32,33]. Therefore, hyperpure chlorine dioxide was used just before blood clot formation in the current case, instead of NaOCl. Chlorine dioxide, a disinfectant used in the food industry and drinking water treatment, has previously been suggested for use in endodontics because of its low toxicity and excellent antimicrobial properties [34, 35, 36, 37]. However, the ordinary solution contains impurities because it is produced by mixing sodium chlorite with an acid [38]. Some of the unknown by-products are suspected to be harmful and carcinogenic [39]. Recently, a novel disinfectant, hyperpure ClO\({}_{2}\) solution (Solumium Pental), was produced and used in endodontics, with a new membrane technology that contains no additional chemicals such as acids. Hyperpure ClO\({}_{2}\) has no significant inhibitory effect on the viability of periodontal ligamental stem cells [11] at the toxic concentration for microbes, due to its size-selective property [12]. Furthermore, ultrasonic activation was performed to increase the effectiveness of the irrigants without increasing their concentration [40]. EDTA was also used to promote stem cell survival and release the growth factors embedded in dentin [41]. The commonly used interappointment medication for RET is triple antibiotic paste because of its bactericidal effect [42]. However, its side effects, such as crown discoloration, allergic reactions, and the development of bacterial resistance, can limit its usage [15]. In this case, Ca(OH)2 was chosen as an intersession medication [15] due to its antimicrobial capacity and ability to stimulate the survival and proliferation of stem cells of the apical papilla [43]. While regenerative endodontic procedures have shown promising results, they also come with several limitations and challenges. Not all cases are suitable for regenerative endodontic procedures, and success depends on the patient's age, root development stage, and inflammation grade [44]. While growing evidence supports the effectiveness of regenerative endodontic procedures [8], long-term clinical studies are still relatively limited [45]. In this study, the presence of new neurons could not be revealed during the control appointments. However, positive sensibility testing can only be achieved in 50% of cases after successful RET [46]. The limitations of the laceration of periapical tissues are the relatively high chance of intracranial calcification and the unpredictable nature of the newly formed tissue [47]. Histological studies have indicated that, in many cases, tissue repair often involves the formation of ectopic cement and bone-like tissue, rather than achieving true tissue regeneration [7; 48; 49]. The mesenchymal stem cells and mature cells from all periapical tissues (bone marrow, cement, periodontal ligament) also enter the root canal and might be responsible for forming the nonendodontic mineralized tissues. Additionally, the amount, type, and potential of stem cells delivered into the root canal space are unknown, and growth factors embedded in dentin could potentially be broken down by irrigants used during root canal treatment [50]. Therefore, new investigations should aim at genuine pulp regeneration by applying components of the tissue engineering triad in an evidence-based way. Numerous preclinical approaches have been introduced, such as applying pure dental stem cells from external sources [5] and using PRF/PRP- or polymer-based synthetic hydrogels as alternative scaffolds [51; 52]. A novel cell-free method for regenerative endodontic therapy involves using secretome-derived products from mesenchymal stem cells [4; 53].