Volumetric Changes After Free Gingival Graft: Tuberosity vs Palatal Donor Site (VolFGG-TP)

BACKGROUND: Free gingival graft (FGG) is a well-established procedure to augment keratinized tissue width and manage gingival recession defects. Despite widespread clinical use, comparative data on volumetric outcomes from different palatal donor sites remain limited, and most existing studies rely on one-dimensional clinical measurements rather than volumetric analysis. Emerging evidence suggests that donor tissue composition may differ between anterior palatal and posterior palatal/tuberosity regions, potentially influencing graft behavior at the recipient site. STUDY DESIGN: Single-center, parallel-group, randomized controlled clinical trial with 1:1 allocation via sealed envelope randomization. INTERVENTION: All surgical procedures were performed by a single operator under local infiltration anesthesia (Ultracain DS, epinephrine 1:200,000). At the recipient site, a split-thickness recipient bed was prepared and the autogenous free gingival graft was stabilized using five 7-0 polypropylene monofilament sutures. Sutures were removed between days 10-14. At the donor site, no sutures were placed and the wound was left to heal by secondary intention. Grafts were harvested aiming for 8x10 mm dimensions. OUTCOME ASSESSMENT: Intraoral scans were acquired at T0 (preoperative baseline), T1 (1 month), T2 (3 months), and T3 (6 months) using a 3Shape TRIOS 5 intraoral scanner and saved as STL files. STL files were superimposed in Exocad using automatic alignment algorithms. Recipient and donor regions of interest were isolated. MeshMixer was used for STL preparation, while final volumetric calculations were performed in Exocad and recorded in mm³. To account for unavoidable minor variations in graft dimensions, volumetric data were mathematically normalized to a theoretical standard graft surface area of 80 mm² (8x10 mm). STATISTICAL ANALYSIS: Sample size was calculated a priori using G\*Power 3.1 (α=0.05, power=0.80, effect size=0.68), yielding 20 patients per group (40 total). Analyses were conducted in SPSS v22.0 with significance set at p\<0.05. Data distribution was assessed using the Shapiro-Wilk test. Within-group time effects were evaluated using Repeated Measures ANOVA; between-group comparisons at each time point were performed using independent samples t-test. Time × donor-site interaction was analyzed to determine whether volumetric change patterns differed between groups over time.