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Impact of Peri-Implant Phenotype on Implant Therapy Outcomes: A 5-Year Cohort Analysis on Soft Tissue—Level Implants

Abstract:

Objective: To investigate the associations between peri-implant phenotype characteristics and long-term outcomes of soft tissue–level implants. Methods: Twenty-five tissue-level implants from a previous controlled clinical trial were evaluated at 1- and 5-year follow-ups after crown delivery. Data included ultrasonographic scans (mucosal thickness and supracrestal tissue height), standardised 2D radiographs, cone beam computed tomography, clinical outcomes (mucosal recession, probing pocket depth, bleeding on probing), patient-reported outcomes and peri-implant health status. Standard logistic and linear regression models were used to analyse associations of implant- and patient-related factors with outcomes, including peri-implant disease status, mucosal recession and marginal bone level (MBL) changes. Results: Five-year implant survival was 100%, with peri-implant mucositis diagnosed in 36% of the implants. Mean MBL changes from the first to the fifth year was 0.29 ± 0.29 mm. Baseline (pre-surgical) buccal soft-tissue thickness < 1.5 mm (OR: 5.20, p = 0.007) and increased plaque scores (OR: 30.11, p < 0.001) were associated with peri-implant mucositis, whereas buccal bone thickness ≥ 1.5 mm (OR: 0.48, p = 0.039), mucosal thickness around implant (OR: 0.20, p = 0.001) and supracrestal tissue height (OR: 0.50, p = 0.002) emerged as protective factors. Mucosal recession was significantly associated with baseline buccal soft-tissue thickness < 1.5 mm (estimate = 0.27, p = 0.03) and keratinised mucosa width of < 2 mm (estimate = 0.39, p = 0.021). Clinical thresholds associated with long-term peri-implant health were defined as follows: supracrestal tissue height ≥ 2.8 mm, restorative emergence angle ≤ 35.5°, mucosal thickness 1.8 mm and buccal bone thickness 1.5 mm. Patients reported a high overall satisfaction (visual analogue scale: 88.2%). Colour Doppler ultrasonography showed a strong correlation between tissue perfusion and peri-implant disease (r = 0.93, p < 0.001). Conclusions: Within the limitations of this study, tissue-level implants showed excellent survival rates and patient satisfaction at 5 years. Several peri-implant parameters—such as supracrestal tissue height ≥ 2.8 mm, restorative emergence angle ≤ 35.5° and buccal bone thickness ≥ 1.5 mm—were associated with favourable outcomes. These exploratory thresholds may be considered hypothesis-generating and could help guide future research and clinical monitoring, although validation in larger cohorts is essential. Trial Registration: www.clinicaltrials.gov/study/NCT02925078.