Impact of Marginal Misfit in Implant-Supported Fixed Dental Prostheses on Peri-Implant Bone Levels: A Retrospective Quantitative Analysis.

Objectives
To evaluate the impact of the marginal fit of implant-supported prostheses (ISP) on peri-implant bone levels. Additionally, the study aimed to determine a clinically relevant threshold for the radiographic vertical misfit gap at the ISP, when present, and to identify potential risk factors associated with changes in bone levels.Methods
This study involved subjects who received ISPs for tooth replacement therapy. Standardized intraoral periapical radiographs were taken 10 years after loading to assess the radiographic distance between the implant shoulder and the most coronal point of crestal bone (DIB). ISP marginal gaps were categorized as no gap or gap, with vertical dimensions categorized as 0 mm, > 0- < 0.1 mm, and ≥ 0.1 mm. A multivariable linear mixed-effect model was applied to control for potential confounders.Results
A total of 301 patients and 505 implants with a 10.6 ± 0.7 years follow-up were analyzed. ISPs without gaps exhibited statistically significantly lower DIB values (3.22 ± 0.8 mm) than those with gaps (3.43 ± 0.6 mm; p = 0.001). Gaps ≥ 0.1 mm were associated with statistically significantly higher DIB values (3.45 ± 0.7 mm; p = 0.001) compared with gaps between > 0 and < 0.1 mm (3.36 ± 0.5 mm; p = 0.001), or no gaps (3.22 ± 0.7 mm; p = 0.001). Each increment of 0.1 mm in the vertical crestal gap corresponded to a significant increase in DIB values (0.08 mm; p = 0.03). Finally, smoking and a history of periodontitis were independent risk factors for increased DIB.Conclusions
Marginal misfit of ISP affects peri-implant bone stability, with gaps ≥ 0.1 mm linked to higher DIB. Smoking and periodontitis are independent risk factors for increased DIB.