Inclusion Criteria:  Age 18+ years Speak and Read English Able to attend follow-up visits at 6 months AND 1 year (post-baseline treatment) A tooth with no response to cold and electric pulp testing. Tooth is a 1st or 2nd mandibular molar Tooth has no response to cold/electric pulp testing Tooth has a diagnosis of pulp necrosis with asymptomatic apical periodontitis 1st and 2nd mandibular molars. Current (i.e., taken within the last week) radiograph available (or done at screening, as needed) A limited-volume, cone-beam computed tomography (CBCT) taken at the first visit confirms apical periodontitis (radiolucency).  Exclusion Criteria:  Patient has advanced untreated periodontal disease/recent periodontal surgery Patient has non-odontogenic facial pan (e.g., face pain of unknown cause) Patient has a history of poor attendance at dental visits Patient is pregnant Patient reports taking corticosteroids Patient is supervised by the Principal Investigator or a member of the research team Patient is subordinate to the Principal Investigator or a member of the research team Patient is a student/trainee under the direction of the Principal Investigator or a member of the research team Tooth had previous intervention (e.g., pulp debridement: removal of the pulp/nerve of the tooth) Tooth has incomplete root formation (e.g., immature with apical periodontitis) Tooth has defective restorations or carious lesions (i.e., cavities) that could lead to microleakage Tooth has internal or external resorption Tooth has a mobility score of 3 Tooth has a fracture/visibly cracked Tooth has vital (i.e., functioning) pulp Advanced untreated periodontal disease or recent periodontal surgery.