Development of a Core Outcome Set in Endodontics (COS-ENDO): Part 2 - COS-ENDO for Studies of Nonsurgical Root Canal Treatment and Retreatment in Permanent Teeth.

INTRODUCTION: Methodological heterogeneity and reporting bias complicate interpreting endodontic outcomes. Supported by the American Association of Endodontists and its Foundation, this study developed the Core Outcome Set in Endodontics (COS-ENDO) to standardize reporting for studies of Nonsurgical Root Canal Treatment/Retreatment, Surgical Endodontics, Vital Pulp Therapy, Apexification, and Regenerative Endodontics. This article, Part 2 of a 5-part series, focuses on COS-ENDO for Nonsurgical Root Canal Treatment/Retreatment, while other parts address the remaining treatments. METHODS: Outcomes were identified through scoping reviews, a qualitative study with patients, and a web-based survey of American Association of Endodontists practicing members. In a 2-round Delphi survey, clinicians, patients, and researchers rated outcomes on a 9-point scale. Ratings were assessed against consensus criteria, and a virtual meeting finalized COS-ENDO. RESULTS: Of the 97 invited participants to Round 1, 77 registered, and 73 (24 Academicians/Researchers, 26 Clinicians, and 23 Patients (or their parents/caregivers)) assessed 39 outcomes, with 18 excluded. The remaining outcomes-7 achieving consensus for inclusion and 14 lacking consensus-advanced to Round 2 for re-rating by 70 participants. This resulted in 9 outcomes achieving consensus for inclusion, and 12 lacking consensus. In the final meeting, 16 participants finalized the COS-ENDO for Nonsurgical Root Canal Treatment/Retreatment, including Tooth survival, Pain, Signs of infection, Radiographic evidence of periradicular healing, Success, Functional tooth, Need for further intervention, and Adverse events/Complications. CONCLUSIONS: COS-ENDO is an important step in standardizing outcome reporting in endodontics, ensuring consistent reporting and enhancing research utility. Further efforts are needed to establish optimal measurement methods.