Interpreting Endodontic–Periodontal Lesions: A Conceptual Framework Based on Pulpal and Periodontal Findings—A Narrative Review

Background/Objectives: Endodontic–periodontal lesions (EPLs) represent complex pathological conditions arising from interactions between endodontic and periodontal infections. Existing classification systems primarily describe the etiology or periodontal tissue destruction but provide limited support for clinical interpretation, particularly pulp preservation and the sequencing of endodontic and periodontal management. This review aimed to propose a biologically informed conceptual framework intended to organize clinical reasoning considerations in EPL management. Methods: This narrative review integrates current knowledge regarding pulp vitality, pathways of infection, periodontal healing, and treatment sequencing reported in the endodontic and periodontal literature. Based on this synthesis, a conceptual framework was constructed using two clinical dimensions: the extent of remaining vital pulp and the presence or absence of coronal-originating infection (IC), defined as a potential coronal pathway of bacterial ingress that may contribute to lesion development. Results: The framework categorizes EPLs into four principal groups according to pulp vitality (vital/non-vital) and IC status (present/absent), with additional grading to describe the potential feasibility of pulp preservation and structural reassessment during initial management. Rather than prescribing specific therapies, the model organizes clinical interpretation related to pulp-preserving considerations, the timing of periodontal intervention, and evaluation of surgical management following nonsurgical treatment. Conclusions: This framework provides a biologically oriented conceptual model for understanding EPLs and structuring clinical reasoning. It is intended as a hypothesis-guided interpretive framework rather than a clinical practice guideline and is designed to support case interpretation, not to determine mandatory treatment decisions; thus, its clinical applicability requires further validation, and prospective multicenter studies are necessary before routine clinical implementation.