Abstract
Introduction: Proper planning, coupled with improved technique, knowledge of the dental anatomy and adjacent structures, commences for successful treatment. In preparing for a prosthesis, we must know how to respect the limits of soft-tissue anatomy. The biological space must be strictly respected, in order that there is harmony between the prosthesis and the soft tissue. Objective: This study aimed to review, through literature, the importance of respecting the limits of the biological space when preparing for a fixed prosthesis. Methods: The PRISMA Guidelines were followed. The search was conducted from January to February 2026 across the Web of Science, Scopus, Embase, PubMed, ScienceDirect, SciELO, and Google Scholar databases. The quality of the studies was assessed using the GRADE instrument, and the risk of bias was evaluated according to the Cochrane instrument. Results and Conclusion: According to the GRADE instrument, most studies presented homogeneous results, with X2 = 65.7% > 50%. A total of 120 articles were found and submitted for eligibility analysis, with 16 final studies selected to compose the results of this systematic review. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 31 studies with a high risk of bias and 28 studies that did not meet GRADE and AMSTAR-2 standards. Information on the biological space and its limits that must be respected is consistent in the literature. Harmony and success of treatment depend on strict planning, adequate materials, and respect for biological limits.