Comparative outcomes of xenogeneic collagen matrices and autogenous graft-based techniques to increase mucosal thickness and keratinised mucosa width at implant sites: are autologous grafts still the gold standard? A systematic review and meta-analysis of randomised clinical trials.

This systematic review compares xenogeneic collagen matrices (XCMs) and autogenous graft-based techniques, focusing on 1) the effectiveness of XCMs (non-crosslinked XCM [XCM*] and crosslinked XCM [VCMX]) vs. connective tissue graft (CTG) for increasing buccal mucosal thickness (MT), and 2) the effectiveness of XCM* vs. free gingival graft (FGG) in augmenting buccal keratinised mucosa width (KMW) at implant sites. MEDLINE (PubMed), Web of Science, and Scopus were searched from inception to August 2024. Randomised controlled trials (RCTs) involving systemically healthy patients with peri-implant mucosal deficiencies (MT <2 mm and/or KMW <2 mm) were included. Studies were required to have 2 parallel control groups comparing XCMs with CTG and/or XCM* with FGG, and a minimum follow-up of 3 months. Data were extracted and analysed using a random-effects model, with risk of bias evaluated via the Cochrane risk of bias tool 2. Seventeen RCTs met inclusion criteria for qualitative synthesis (XCMs vs. CTG, n=12; XCMs vs. FGG, n=5), with 14 RCTs included in the meta-analysis (XCMs vs. CTG, n=9; XCMs vs. FGG, n=5). Subgroup analysis of XCM* or VCMX vs. CTG showed a significantly greater MT increase with CTG than with XCM* (pooled mean difference [MD], 0.27; 95% confidence interval [CI], 0.05 to 0.49;