Efficacy of Collagen Matrix for Establishing Keratinized Mucosa at Dental Implants: A 5‐Year Randomized Controlled Trial

ABSTRACT Objectives To compare the 5‐year outcomes of collagen matrix (CM) and free gingival graft (FGG) used to augment the keratinized mucosa (KM) around posterior dental implants. Materials and Methods Thirty patients (44 implants) with inadequate KM (< 2 mm) on posterior dental implants were randomized into two groups that received KM augmentation with CM or FGG. Clinical measurements comprising the KM width (KMW), buccal mucosal thickness (MT), and clinical parameters were examined in a 5‐year follow‐up. Marginal bone loss (MBL) was evaluated with standardized radiographs using the paralleling technique. Patient‐reported outcomes (PROs) during the first week post‐surgery and at the 5‐year follow‐up were evaluated. Results KMW increased significantly during the follow‐up period in both groups. The FGG group had a significantly greater KMW than the CM group at the 1, 2‐month follow‐up and after the 6‐month follow‐up. KM shrinkage was observed, and was greatest within the first 2 months post‐surgery in both groups. At the 5‐year follow‐up, the KM shrinkage was significantly different between the groups (FGG: 47%; CM: 70%) ( p < 0.01). The MT increased significantly in the FGG group. The clinical parameters and MBL were similar between the groups. The bleeding score in the FGG group was higher than that in the CM group ( p < 0.05) within the first 2 days post‐surgery, while other PROs scores were similar between groups in the first week post‐surgery. At 5‐year follow‐up, all patients were highly satisfied with the treatments. Conclusions FGG was superior to CM in terms of the KM augmentation and MT increase. Except for a slight difference in self‐reported bleeding during the first two post‐operative days, CM didn't demonstrate other significant advantages in PROMs. Trial Registration ChiCTR1800018285 (date of registration: 9/9/2018, retrospectively registered. URL: https://www.chictr.org.cn/showproj.html?proj=24156 )