Tissue integration and vascularization of volume collagen matrices and connective tissue grafts following peri-implant soft tissue augmentation

This study aimed to histologically reanalyze tissue integration and vascularization of volume collagen matrices (VCMX) and subepithelial connective tissue grafts (SCTG) at 3 and 4 months following peri-implant soft tissue augmentation. Peri-implant soft tissue augmentation was performed with VCMX or SCTG and biopsies were harvested at 3 and 4 months. Secondary analyses included descriptive histology, blood vessel count and tissue composition [remaining matrix, peri-implant connective tissue containing 3 different components (collagen bundles, elastic connective tissue and loose connective tissue), elastic fibers and background]. A total of 21 samples were analyzed (VCMX: 6/9 biopsies at 3/4 months; SCTG: 6 biopsies at 3 months). Compared to SCTG, VCMX sites displayed fewer and smaller blood vessels within denser tissue. Collagen bundles in VCMX were thicker, whereas SCTG sites displayed a looser tissue structure. The proportion of elastic connective tissue were 22.5% (VCMX/3 months), 32,7% (VCMX/4 months) and 17.4% (SCTG/3 months). Additionally, VCMX samples at 3 months also showed the highest proportion of elastic fibers (10,7%). Peri-implant soft tissue augmentation with VCMX resulted in reduced vascularization but increased tissue density compared to sites augmented with SCTG.