the dentin. hence, contemporary regenerative endodontics originates from the trauma literature and embarks into the field of tissue engineering. regeneration indicates an overall objective of reproducing the original tissue histology and function. to date, tissue engineering appears to offer the greatest opportunity for regeneration. since high concentrations of stem cells are delivered into the root canal space when lacerating the apical papilla in the immature permanent tooth, this clinical procedure accomplishes one major element of the triad of tissue engineering. ongoing research has evaluated combinations of stem cells, growth factors, and scaffolds that result in histological regeneration of pulp tissues. on the contrary, the concept of revascularization focuses only on the delivery of blood into the root canal space to allow the pulp space to be filled with vital tissue as a means of prompting wound healing. therefore, a focus on “revascularization” would disregard the potential role of growth factors and scaffolds in histological recapitulation of the pulp-dentin complex. although angiogenesis and the establishment of a functional blood supply is a key feature in the maintenance and maturation of a regenerating tissue, positive responses to pulp sensitivity tests such as cold or ept have been reported in some of the published cases. this indicates that a space that was previously vacant (debrided root canal) may become populated with an innervated tissue supported by vascularity. taken together, the core concepts of tissue engineering distinguish a regenerative treatment paradigm from a revascularization philosophy. treatment plan the primary concern in regenerative endodontics is to promote healing of the diseased tissues, prevention of relapse or recurrence of the disease, and patient well-being (patient centered). thus, the primary therapeutic goal of regenerative endodontic procedures is to promote the healing, survival and function of the tooth. a study showed that regenerative endodontic procedures had better clinical outcomes as compared to apexification procedures, both with mineral trioxide aggregate and calcium hydroxide such as in aspects of absence of pain, swelling and sinus tracts. the secondary therapeutic goal of regenerative endodontic procedures is continued root development. a study has shown that teeth treated with revascularization showed a significantly greater percentage increase in root length compared with teeth treated by either mineral trioxide aggregate or calcium hydroxide apexification. regenerative procedures promoted a decrease in apical diameter (apical closure). root development allows the increase of the resistance to fracture and improve the tooth survival rate. the tertiary therapeutic goal of regenerative endodontic procedures is return of pulp vitality. regenerative endodontic procedures suggests that free nerve endings of the root end are guided into the canal by specific chemical signals. nonetheless, the presence of nerve endings suggests the presence of a vital tissue that is immune-competent due to the intimate association of innervation with blood vessels and the immune system. it also suggests the recovery of sensation that is important for the detection of actual or potential injury to the tooth organ. clinical outcomes regenerative endodontic procedures is a new treatment option which must be objectively compared with the longer established, more traditional endodontic treatment procedures for immature teeth, known as apexification procedures. the primary goal of any endodontic therapy is the resolution of infection and the signs and symptoms of inflammation leading to apical periodontitis. regenerative endodontic procedures depend on efficient and powerful chemical disinfection, which is then followed by the repair and growth of the tooth that promotes continued root development and re-establishment of nerve functions of the tooth. however, pulpal necrosis in immature teeth often results in incomplete root development. these teeth often have thin root canal walls which are susceptible to fracture after treatment. therefore, complete cleaning and shaping as well as obturation of these teeth are difficult or sometimes impossible, due to high risk of fracture during the procedure clinical outcome of regenerative endodontics can be observed within 6 months of treatment such as no pain, soft-tissue swelling, or sinus tract. radiographic outcomes such as resolution of apical radiolucency are often observed by 6 months (aae).various studies on regenerative endodontics have shown resolution of periapical radiolucency at 6-month follow-up. regenerative endodontic procedure regenerative endodontics has 3 critical steps: adequate disinfection of the root canal system, induction of bleeding through overinstrumentation to create a scaffold for stem cells, and coronal sealing of the blood clot with a biocompatible material, such as mineral trioxide aggregate. the procedure is applied in two visits as follows: during the first visit, after local anesthesia injection; isolation of the tooth is done with a rubber dam, and access is performed with a cutting instrument, which is a round bur to remove the dead pulp. then, irrigation of the canal is carried out with sodium hypochlorite solution and physiological saline, which is later dried and intracanal medicament (such as triple antibiotic paste) is placed into the canal. the tooth is temporarily sealed for 1 to 4 weeks. during the second visit, which is after 3 weeks, the tooth was accessed for any signs and symptoms. hence, the asymptomatic tooth is proceeded to the next step of regenerative endodontic treatment. bleeding was induced by overinstrumenting beyond the root with a thin instrument (known as file)) to form a blood clot. then, an absorbable collagen barrier is placed above the blood clot followed with mineral trioxide aggregate and glass ionomer cement. the patient is then recalled after 7 days to ensure setting of the filling material of mineral trioxide aggregate, and replacement of the glass ionomer cement with composite resin. follow-up observation and measurement radiograph images, before and after the procedure are used to evaluate the outcome of the treatment. the patients are scheduled to follow up at 3, 6, 9, and 12 months after the completion of therapy. the tooth is accessed for different aspects such as pain, swelling, sinus tract, mobility, tooth discoloration, and the occlusion relationship. at the 12-month follow-up, cbct images are taken to analyze the root development, in specific to access for the disappearance of apical radiolucency, increase of root length or a decrease of the apical foramen, or both. clinically, regenerative endodontic treatment is carried out in teeth with necrotic pulps and immature apices. in order to promote pulp regeneration in infected root canals, greater efficiency of disinfection is required. disinfecting agents for regenerative procedures include sodium hypochlorite, antibiotic or calcium hydroxide dressings. although sodium hypochlorite has antimicrobial effect, it has detrimental effects to the stem cells at the end of the tooth, which can hinder survival and differentiation of these cells. therefore, sodium hypochlorite is advised to be used at a lower concentration so as to achieve the optimum effect for antimicrobial activity and differentiation of the stem cells. besides, mineral trioxide aggregate is used as the coronal barrier on the blood clot due to its biocompatibility, and its ability to promote cell differentiation and hard tissue production without adverse tissue reactions. advantages there are some benefits of regenerative endodontics such as: revitalization of the tooth, continued root development and, potentially, increasing fracture resistance. regenerative endodontic treatment helps in true pulpal regeneration and re-establishment of the pulp-dentin complex, which leads to revitalisation of the tooth. it may be an alternative treatment option in the management of root resorption especially when the prognosis is deemed poor because of severe resorption. research king's college london published in january 2017 on the regeneration of dentine with collagen sponge filled with glycogen synthase kinase (gsk-3) .