Influence of Marginal Tooth Preparation Designs on Periodontal Health and Long-Term Stability: A Narrative Review

Background: Tooth preparation design strongly influences the long-term success of fixed prosthodontic restorations, affecting periodontal stability and esthetic outcomes. Conventional horizontal designs such as chamfer and shoulder remain widely used but present biological and technical limitations. The Biologically Oriented Preparation Technique (BOPT), a vertical approach, has been proposed as an alternative. Methods: This narrative review synthesizes evidence from clinical trials, histological investigations, and systematic reviews, comparing horizontal preparations with BOPT with emphasis on periodontal parameters and the role of digital workflows. Results: Horizontal designs provide predictable outcomes but may predispose to inflammation and marginal instability, especially with subgingival margins. BOPT has been associated with greater gingival thickness, stable probing depths, and favorable esthetic results, with prospective studies reporting stability for up to 10 years. Integration with CAD/CAM workflows appears to enhance precision and reproducibility. Conclusions: BOPT shows promising periodontal and esthetic benefits, particularly in thin gingival biotypes and esthetically demanding cases. However, current evidence is limited, and the available studies do not allow firm conclusions about superiority over conventional designs. Further randomized controlled trials with large cohorts and long-term follow-up are required before definitive clinical recommendations can be made.