The purpose of this study is to develop new improved therapy for teeth that require root canals due to tooth infection or tooth inflammation. Investigators will recruit total of 50 participants from the age group 7 - 50 at the UCLA School of Dentistry Endodontic clinic. The participants will be divided into two groups, one will receive traditional therapy, which may include root canal or a procedure called "revascularization," which is a procedure trying to regrow the tissue inside the tooth. The other group of participants will receive the test treatment, which will involve harvesting of pulp tissues from the same tooth or other teeth that are planned for extraction. Investigators will prepare these tissues and place the tissues back into the cleaned root canal space with induced bleeding to allow regrowth of the tissue. For all participants, investigators will follow up after 6, 12, and 24 months in a shorter appointment, which may involve taking x-ray and clinical exam.

The goal of the study is to test whether autologous pulpal mesenchymal stem cells (MSCs) is capable of de novo regeneration of pulp-dentin complex and restoration of normal pulp physiology in teeth with necrotic or inflamed pulp. This is a highly novel study that will bring the regenerative endodontic approaches to the next level. Furthermore, revascularization approaches, as delivered in today's endodontic offices, present several challenges, including lack of de novo pulp-dentin regeneration, and frequent occurrence of intracanal calcification. These findings attest to the limitation of revascularization as a regenerative endodontic procedure (REP) and necessitates advent of novel approach for functional restoration of dental pulp. The ultimate objective of the current study is to develop a new REP that allows for de novo regeneration of functional dental pulp, which can be readily performed in a chair-side manner.

Inclusion Criteria:

• Healthy male or female participants at ages of 7 - 50 y.o. presenting with a tooth diagnosed with complete or partial necrosis of the pulp or irreversible pulpitis.
• Participants presenting with donor pulp tissue, either from existing deciduous teeth or from permanent teeth treatment planned for extraction, e.g., second premolars for orthodontic extraction or third molars.
• Participants presenting with irreversible pulpitis and partial necrosis, i.e., visible pulpal tissues during access opening and canal debridement.
• Participants with immature root apices, including those with partially closed apex, that require root canal procedure.

Exclusion Criteria:

• Participants with any systemic conditions preventing routine dental procedures or requiring medication that interfere with healing or induce bleeding.
• Participants with avulsed, replanted teeth with resultant pulp necrosis.
• Participants with vertical root fracture/cracks.
• Participants with teeth that are not restorable.

Randomized