This diagnostic test accuracy (DTA) study aims to evaluate the diagnostic performance of educated large language models (Educated ChatGPT (GPT-5.5 Pro), Educated Gemini 3.1 Pro, and Educated Claude Opus 4.7) in endodontic practice. Their ability to establish pulpal and periapical diagnoses and assess endodontic case difficulty will be compared with the reference standard established by a panel of endodontic experts. Clinical and radiographic information from patients presenting for primary endodontic treatment or nonsurgical endodontic retreatment will be provided to both the AI models and the expert panel. The primary outcomes are the sensitivity, specificity, and the overall accuracy of the educated LLMs, with the objective of determining their potential role as reliable decision-support tools in endodontic diagnosis and treatment planning.