* This study will enroll approximately 12 endodontists (primary subjects) and approximately 120 patients (secondary subjects) undergoing routine endodontic treatment (primary root canal treatment or retreatment), resulting in approximately 120 observed treatment sessions. Patients will be treated as part of standard clinical care and will not receive any experimental intervention.
* Participating endodontists will wear an Apple Watch to continuously monitor heart rate (HR) during routine endodontic procedures. The Apple Watch contains built-in physiological sensors that automatically record heart rate. HR data are stored locally in the Apple Health app on a study-designated iPhone assigned for research use and handled solely by the Principal Investigator (PI). No real-time data transmission or cloud-based sharing occurs during data recording. At designated intervals, the PI will use the Apple Health app's built-in "Export Health Data" function, which generates a ZIP file containing an export.xml file with sensor-recorded data. The ZIP file will be uploaded directly from the study iPhone to a secure, university-approved UI Box Health Data Folder designated for the study. No research-specific Apple ID, cloud account, or third-party data-sharing platform will be used.
* A trained, non-intervening observer will record start and stop timepoints of predefined endodontic treatment stages to align HR signals with procedural phases. These stages include patient presentation, examination, informed consent, local anesthesia administration, rubber dam placement, access cavity preparation, root canal instrumentation, obturation, and final radiographic assessment. The observer will document only minimal, non-identifiable procedural variables necessary for analysis, including treatment type (primary root canal treatment or retreatment), treatment difficulty level (based on the AAE Endodontic Case Difficulty Assessment), and patient age category. No patient identifiers or protected health information (PHI) will be recorded.
* Each participating endodontist will complete the Perceived Stress Questionnaire (PSQ) two times in total at baseline and at the conclusion of study participation to assess perceived stress levels and evaluate associations between baseline stress and physiological stress responses during treatment. The PSQ requires approximately 5 minutes to complete. Endodontists will not complete questionnaires for individual patient encounters. HR data and permitted procedural variables will be coded, securely stored in the UI Box Health Data Folder, and analyzed to assess HR variation across endodontic treatment stages and treatment difficulty levels. No additional patient identifiers or PHI will be collected beyond what is specified above.