Risk factors for open gingival embrasures in the mandibular central incisor region among adult non-extraction patients treated with clear aligner therapy

To investigate the incidence and risk factors of open gingival embrasures (OGEs) in the incisor region after treatment with clear aligners in adult non-extraction patients and provide a reference for preventing the occurrence of an open gingival wedge gap in the incisal area after orthodontic treatment.

This study has been reviewed and approved by the institutional medical ethics committee, and informed consent was obtained from the patients. A total of 125 adult patients with malocclusion who completed clear aligner treatment at Hefei Stomatological Hospital from September 2022 to December 2024 were selected as the study subjects. Based on the presence or absence of OGEs in the incisor region observed in frontal intraoral photographs taken immediately after treatment completion, the patients were divided into a normal group and an OGE group. Clinical data, including intraoral photographs, digital models, and cone-beam computed tomography before and after treatment, were analyzed. Measurements such as incisor overlap and rotation, crown morphology, number of attachments, and interproximal enamel reduction (IPR) were recorded and analyzed.

The incidence of OGEs between the maxillary and mandibular central incisors after clear aligner treatment in adult patients was 28.8% and 39.2%, respectively. No statistically significant differences were observed between the normal and OGE groups in terms of sex, Angle's classification, gingival biotype, overbite, overjet, IPR amount, age, treatment duration, tooth axis angulation, or horizontal movement distance of mandibular central incisors before and after treatment (P > 0.05). However, significant differences were found in the number of attachments, anteroposterior distance between mesial incisal angles, distance from the interproximal contact point (ICP) to the alveolar bone crest (ABC) (ICP-ABC), horizontal distance between mesial cementoenamel junction (CEJ) of two adjacent central incisors (CEJ-CEJ) and labial alveolar bone thickness (P < 0.05). IPR amount and mandibular incisor intrusion were significantly associated with the severity of OGEs (P < 0.05). Regression analysis revealed that the number of attachments, anteroposterior distance between mesial incisal angles, ICP-ABC distance, and CEJ-CEJ horizontal distance were significantly correlated with the occurrence of OGEs.

The incidence of open gingival embrasures in the mandibular central incisor region is relatively high among adult patients treated with clear aligners. The number of attachments (n = 2), the anteroposterior distance between the mesio-incisal angles, the distance from the tooth contact point to the alveolar bone crest, and the horizontal distance between adjacent cementoenamel junctions have been identified as risk factors for the development of open gingival embrasures upon completion of orthodontic treatment.