The most typical cause of the pulp-periapical disease is caries. Because the infected or non-infected necrotic pulp tissue in the root canal system is not accessible to the host's innate and adaptive immune defense mechanisms and antimicrobial agents, root canal therapy is the only option for treatment when the pulp tissue involved in caries becomes irreversibly inflamed and progresses to necrosis. Therefore, pulpectomy is required to remove the necrotic pulp tissue from the canal space, whether it is diseased or not. For many years, endodontists have been searching for biologically based therapy methods that could encourage regeneration or repair of the dentin-pulp complex that has been damaged by trauma or infection. The dental stem cells that can regenerate the dentin-pulp complex were found after a protracted, exhaustive search in vitro laboratory and in vivo preclinical animal tests. As a result, the biological idea of "regenerative endodontics" evolved, highlighting a paradigm shift in the way clinical endodontics treats young permanent teeth with necrotic pulps
