Protective factors and critical mucosal thickness for the stability of the peri‐implant soft tissue margin over 5 years: A longitudinal cohort study

Abstract Background Peri‐implant soft tissue dehiscence deficiencies (PSTDs) are common esthetic complications in the anterior maxilla, yet the parameters that protect the peri‐implant soft tissue margin (STM) over time remain unclear. Previous studies have identified several risk indicators, but longitudinal thresholds capable of predicting stable STM have not been established. This study aimed to evaluate 5‐year STM behavior and identify clinically meaningful predictors of long‐term stability. Methods This prospective longitudinal study included patients with anterior single implants with or without PSTD. Clinical and ultrasonographic examinations were performed at baseline ( T 0 ) and 5 years ( T 5 ), and included STM stability (primary outcome), PSTD incidence, mucosal thickness at 1 and 3 mm from the STM (MT1 and MT3), keratinized mucosa (KM) width, buccal bone thickness (BBT), and buccal bone dehiscence (BBD). Logistic regression, receiver operating characteristic curve (ROC) analysis, stratified subgroup analysis, and correlation testing were performed. Results A total of 133 implants in 124 patients were evaluated. PSTD prevalence increased from 51.1% at T 0 to 74.4% at T 5 , (incidence 47.7%). MT3 was the dominant predictor of STM stability (AUC = 0.998). The optimal statistical threshold was 2.01 mm, while a clinical stability threshold of 2.23 mm yielded 100% stability in this dataset. Other predictors (MT1, KM, BBT) were significant only in univariate models. In implants without PSTD at T 0 , MT3 alone predicted stability, whereas in implants with PSTD at T 0 , multiple variables influenced STM outcomes. Conclusions MT3 is the critical determinant of 5‐year STM stability at anterior implants. In our cohort, achieving a MT3 ≥ 2.23 mm was found to be associated with a long‐term stable peri‐implant soft tissue.