Peri-implant soft tissue thickness following connective tissue grafting or volume-stable collagen matrix augmentation: A randomized controlled trial

BACKGROUND: Peri-implant soft tissue thickness (STT) is considered as an important factor influencing marginal bone stability and esthetic outcomes; however, the effectiveness of different augmentation materials and the impact of augmentation timing remain unclear. OBJECTIVES: The aim of this study was to compare changes in peri-implant SST following augmentation with a subepithelial connective tissue graft (CTG) or a volume-stable collagen matrix (VCMX) vs. non-augmented control sites, and to explore the potential influence of augmentation timing. MATERIAL AND METHODS: In this randomized controlled clinical trial (RCT), 36 patients with 40 implant sites in the esthetic zone were allocated to the CTG (n = 16), VCMX (n = 16) or non-augmented control (n = 8) groups. Within the CTG and VCMX groups, implant sites were further subdivided according to augmentation timing (staged vs. simultaneous), with each subgroup consisting of 8 implant sites. Soft tissue augmentation was performed either prior to implant placement or simultaneously with implant insertion. Soft tissue thickness was assessed using standardized ultrasonographic measurements at baseline (T0), 3 months (T1) and 12 months (T2). Marginal bone loss (MBL) and complications were recorded as secondary outcomes. RESULTS: Both augmentation methods resulted in significantly greater SST as compared to non-augmented sites (p < 0.001). At T2, CTGs tended to achieve greater final thickness than the collagen matrix (a difference of 0.3-0.6 mm in the final SST). All augmented sites exceeded 2 mm mucosal thickness. No statistically significant differences related to augmentation timing were detected. Marginal bone loss was low and comparable among the groups, and no biological or technical complications were observed. CONCLUSIONS: Soft tissue augmentation results in clinically relevant and stable increases in peri-implant tissue thickness. Connective tissue grafts tended to provide greater final thickness, whereas the collagen matrix may represent a reliable and less invasive alternative. No statistically significant influence of augmentation timing on the final STT outcomes was detected over 12 months.