Prevalence of gingival recession and its associated risk factors in the mandibular central incisors of Chinese patients following fixed orthodontic treatment: a retrospective study

This retrospective study was designed to describe and compare the prevalence and severity of gingival recession (GR) in the mandibular central incisor region. Additionally, it sought to identify potential risk factors associated with GR. According to the selection criteria, a total 286 Chinese patients who had completed fixed orthodontic treatment between January 2019 to March 2024, 123 males (43.0%) and 163 females (57.0%), were included in the study. The following parameters were assessed: gingival recession depth (GRD), gingival biotype (GBT), keratinized gingival width (KGW), incisor-mandibular plane angle (IMPA), and labial alveolar bone thickness at the alveolar ridge crest, middle, and apical region (LBT-crest, LBT-mid, LBT-apex). Data were obtained anonymously from the pre-treatment (T0) and post-treatment (T1) archival records. Based on the difference in IMPA between T1 and T0, subjects were categorized into protrusion and retrusion groups. Statistical analyses were performed using the independent sample t-test, Mann-Whitney U test, and Pearson’s chi-square test. Logistic regression analyses identified the risk factors for GR. Receiver operating characteristic (ROC) curves were employed to determine the optimal cut-off values for the high-risk factors of GR. There were 75 subjects (26.2%) with GR and 211 participants (73.8%) without GR at T1, all of whom had ideal gingival margin positions at T0. The protrusion group had a significantly higher GRD (0.31 ± 0.52 mm) than the retrusion group (0.06 ± 0.12 mm, P < 0.05). However, no significant difference in the occurrence rate of GR was observed between the two groups (P > 0.05). Compared to GR patients, non-GR subjects exhibited statistically lower ∆IMPA values, higher KGW, LBT-crest, LBT-mid, and LBT-apex. Furthermore, statistically significant associations was found between the occurrence of GR following orthodontic treatment and GBT, KGW and LBT-crest. The optimal cut-off values for KGW (T0), KGW (T1), LBT-crest (T0), and LBT-crest (T1) were 2.70 mm, 2.23 mm, 0.72 mm, and 0.73 mm, respectively. Thin GBT, narrow KGW, and thin LBT-crest may increase the risk of GR. A minimum LBT-crest of 0.72 mm and KGW of 2.70 mm prior to orthodontic treatment may effectively prevent the occurrence of GR.