BackgroundEmerging clinical data points to the relevance of the presence of keratinized tissue (KT). Although apically positioned flap/vestibuloplasty along with free gingival graft (FGG) is considered as a standard intervention for augmenting KT, substitute materials appear to be a viable treatment alternative. So far, there is a lack of data investigating the dimensional changes at implant sites treated with soft-tissue substitutes or FGG.AimThe present study aimed at comparing three-dimensional changes of a porcine derived collagen matrix (CM) and FGG for increasing KT at dental implants over a 6-month follow-up period.Materials and MethodsThe study enrolled 32 patients exhibiting deficient KT width (i.e., < 2 mm) at the vestibular aspect who underwent soft tissue augmentation using either CM (15 patients/23 implants) or FGG (17 patients/31 implants). The primary outcome was defined as tissue thickness change (mm) at treated implant sites between 1- (S0), 3- (S1), and 6-months (S2). Secondary outcomes considered changes of KT width over a 6-month follow-up period, surgical treatment time, and patient-reported outcomes.ResultsDimensional analyses from S0 to S1 and from S0 to S2 revealed a mean decrease in tissue thickness of − 0.14 ± 0.27 mm and − 0.04 ± 0.40 mm in the CM group, and − 0.08 ± 0.29 mm and − 0.13 ± 0.23 mm in the FGG group, with no significant differences noted between the groups (3 months: p = 0.542, 6 months: p = 0.659). Likewise, a comparable tissue thickness decrease was observed from S1 to S2 in both groups (CM: − 0.03 ± 0.22 mm, FGG: − 0.06 ± 0.14 mm; p = 0.467). The FGG group exhibited a significantly greater KT gain after 1, 3 and 6 months compared to the CM group (1 month: CM: 3.66 ± 1.67 mm, FGG: 5.90 ± 1.58 mm; p = 0.002; 3 months: CM: 2.22 ± 1.44; FGG: 4.91 ± 1.55; p = 0.0457; 6 months: CM: 1.45 ± 1.13 mm, FGG: 4.52 ± 1.40 mm; p < 0.1). Surgery time (CM: 23.33 ± 7.04 min.; FGG: 39.25 ± 10.64 min.; p = 0.001) and postoperative intake of analgesics were significantly lower in the CM group (CM: 1.2 ± 1.08 tablets; FGG: 5.64 ± 6.39 tablets; p = 0.001).ConclusionsCM and FGG were associated with comparable three-dimensional thickness changes between 1 and 6 months. While a wider KT band could be established with FGG, the use of CM significantly reduced surgical time and patients´ intake of analgesics.Graphical abstract