Soft Tissue Augmentation at Single Implants With Collagen Matrix or Connective Tissue Graft: 7.5-Year Follow-Up of a RCT

Abstract

Aim: To compare up to 7.5-year clinical and patient-reported outcomes of implant sites previously augmented using a volume-stable collagen matrix (VCMX) or connective tissue graft (SCTG) in the esthetic zone. Methods: The original randomized controlled trial (RCT) enrolled 20 patients who received soft tissue augmentation with VCMX or SCTG at single implant sites. Clinical assessments and standardized measurements were performed at baseline after crown insertion (BL) and at 6 months, 1, 3, 5, and 7.5 years. The primary outcome was mucosal thickness. Secondary outcomes included marginal bone levels, probing depth, bleeding on probing, plaque index, pink esthetic score (PES), OHIP-14, and buccal profilometric changes. Group comparisons were performed using mixed-effects and generalized estimating equation (GEE) models, which account for within-patient correlations due to repeated measurements and allow inclusion of all available data without requiring imputation for missing observations. Results: Of the 20 originally recruited patients, 12 were available for re-examination at 7.5 years (five in the SCTG group and seven in the VCMX group). Mucosal thickness at crown delivery ranged from 2 to 4 mm across the study population. Adjusted mean differences (VCMX-SCTG) in mucosal thickness were +0.70 mm at BL, -0.02 mm at 6 months, +0.1 mm at 1 year, +0.1 mm at 3 years, +0.1 mm at 5 years and -0.1 mm at 7.5 years. None of these differences reached statistical significance (p > 0.05). For all secondary outcomes, no statistically significant inter-group differences were detected (p > 0.05) except for BOP at 5 years follow-up. Conclusion: Both augmentation approaches achieved stable peri-implant mucosal dimensions, preserved marginal bone levels, and favorable esthetic and patient-reported outcomes over 7.5 years. Volume-stable collagen matrices might be a viable alternative to SCTG for peri-implant soft-tissue augmentation; however, adequately powered RCTs are needed to confirm these long-term observations.