Volumetric changes of porcine collagen matrix and free gingival grafts for soft-tissue grafting to increase the width of keratinized tissue around dental implants: a retrospective clinical study

Aim: To compare three-dimensional changes of aporcine derived collagen matrix (CM) and free gingival grafts (FGG) for increasing keratinized tissue (KT) at dental implants over a 24-month follow-up period.

Materials and methods: This retrospective study enrolled 25 patients exhibiting 41 implants with deficient KT width (i.e., < 2 mm) who underwent soft tissue augmentation using either CM (11 patients/15 implants) or FGG (14 patients/26 implants). The primary outcome was tissue thickness change (mm) at treated implant sites between 1- (S0), 12- (S1), and 24-months (S2). Secondary outcome was the changes of KT width over a 24-month follow-up period.

Results: Dimensional analyses from S0 to S1 and from S0 to S2 revealed a mean decrease in tissue thickness of -0.05 ± 0.35 mm and - 0.31 ± 0.41 mm in the CM group, and - 0.23 ± 0.38 mm and - 0.22 ± 0.81 mm in the FGG group, with no significant differences found between the groups (S0-S1: p = 0.14, S0-S2: p = 0.58). Within S1 and S2, the CM and FGG groups displayed comparable tissue thickness reduction (CM: -0.32 ± 0.53 mm, FGG: -0.02 ± 0.21 mm; p = 0.07). The FGG group exhibited a significantly greater KT gain 24-months compared to the CM group (CM: 1.50 ± 1.14 mm, FGG: 4.04 ± 1.65 mm; p < 0.001).

Conclusions: CM and FGG were associated with comparable three-dimensional thickness changes over a period of 24 months. A significantly wider KT band could be established in the FGG group.