Objective: This Methods: Twenty-six patients (18 females and 8 males; aged 11-25 years) with normally positioned mandibular incisors, defined by an initial 1-NB distance of 3-5 mm, were included. All patients received non-extraction fixed orthodontic treatment with the straight-wire technique. Gingival recession was clinically recorded at treatment onset (T0) and 20 days after appliance removal (T1). Gingival thickness was measured by transgingival probing at two labial sites on each mandibular anterior tooth: one apical to the free gingival groove and one coronal to the mucogingival junction. The T0-T1 changes were analyzed using paired samples t-tests; intergroup gingival thickness comparisons were analyzed using independent samples t-tests or Mann-Whitney U tests, with a Bonferroni correction where appropriate. Results: The mean treatment duration was 28.26 months. The 1-NB distance increased significantly from 4.05±0.94 mm to 4.67±1.51 mm (p=0.003), whereas the 1-NB angle and the incisor mandibular plane angle changes were not significant. No clinical gingival recession was detected at T1. Significant tooth- and level-specific changes in gingival thickness were observed. Conclusion: Within this sample and observation period, no clinical gingival recession was observed after treatment. However, changes in gingival thickness indicate that labial gingival thickness should be considered during orthodontic treatment planning and periodontal monitoring.