A Three-Zone Classification System for Biomaterial-Based Management of Deep Subgingival Carious Lesions

Background: This article introduces a clinically oriented, anatomy-based classification of subgingival margins. The proposed system categorizes margins into distinct zones based on their relationship with gingival and periodontal tissues and links each zone to appropriate restorative strategies. Methods: The classification is based on established principles of periodontal anatomy and restorative dentistry, as well as clinical considerations related to accessibility, isolation, and matrix placement. Three zones are proposed: (1) margins located within the free gingiva, which are generally accessible and manageable with rubber dam isolation; (2) margins extending into the junctional epithelium and supracrestal tissue attachment, where additional measures, including matrices and wedges, are often required to achieve adequate isolation and adaptation; and (3) margins located at or below the alveolar bone crest, which have traditionally required surgical management but may, in selected cases, be managed with advanced matrix techniques. Results: The proposed classification helps clinicians assess the complexity of subgingival margins before performing deep margin elevation (DME) and provides guidance for selecting appropriate clinical procedures according to margin depth and anatomical location. Conclusions: This classification provides a practical framework for selecting appropriate isolation techniques and treatment strategies to improve the predictability of restorative outcomes. Further clinical research is needed to evaluate its validity and its effects on periodontal health and long-term restorative outcomes.