Purpose: In the present study, biological width is considered a specific concept, revealing the relationship between its vertical dimension and structure and its ability to provide internal environment integrity and thus protect the underlying tissues and prevent marginal bone resorption. The study aims to assess the dynamics of marginal bone resorption depending on biological width violation.

Materials and Methods: Forty-three patients with 97 implants were included in this study. The marginal bone level and biological width dimension were evaluated based on clinical and radiographic examinations performed after implant placement and every follow-up thereafter. The biological width violation was diagnosed when the distance between the marginal bone level and free mucosa margin was less than 3 mm and/or connective attachment was absent. The clinical data were processed using linear mixed-effects model statistics at the patient level.

Results: The mean change in the marginal bone level after three years in function was −0.36 ± 0.57 mm, and −0.13 ± 0.42 mm taking implant and prosthesis placement baselines, respectively. The highest marginal bone resorption was determined in implants with the strongest violated biological width, both due to their peri-implant mucosa insufficient dimension (< 3 mm) and the absence of effective connective tissue attachment. In contrast, a significant decrease (p = 0.0002) in marginal bone resorption was observed in implants where biological width was fully respected in terms of a peri-implant mucosa sufficient dimension (> 3 mm) and the presence of an effective connective tissue attachment.

Conclusion: This study demonstrated that direct contact of connective tissue with the structured, bioactive, moderately rough neck surface of a two-stage fixture during (supra-, equi-crestal) placement significantly reduces marginal bone resorption during biological width restoration in patients with a thin and thick gingival biotype. A positive correlation between biological width violations and marginal bone resorption was documented.