Incidence and risk factors of open gingival embrasures in Invisalign extraction cases: a retrospective cohort study

Aims To assess the incidence of open gingival embrasures (OGE) between central incisors and identify significant patient- and treatment-related factors associated with OGE in Invisalign® cases involving four premolar extractions. Methods A total of 97 patients (13 males, 84 females; mean age 22.74 ± 6.47 years) who underwent Invisalign® treatment with extraction of four first premolars were retrospectively included. Post-treatment intraoral photographs were evaluated to assess the occurrence of OGE between maxillary and mandibular central incisors, categorizing patients into Normal and OGE groups. Patient-related factors — including age, gender, molar relationship, crown morphology, Wits appraisal, and sagittal/vertical skeletal patterns — and treatment-related factors — encompassing treatment duration, attachment design, ClinCheck®-programmed central incisor movements, and actual movements measured via lateral cephalometric superimposition — were compared between groups. Significant contributing factors were further identified using both simple and multivariable binary logistic regression analyses. Results The incidence of OGE between central incisors was 18.56% in the maxilla and 42.27% in the mandible. Crown morphology, horizontal movement and differential movement of rotation were significantly associated with the occurrence of OGE between maxillary central incisors. While in the mandible, the occurrence of OGE was mainly related to differential movement of buccolingual crown translation and horizontal movement. Conclusions The incidence of OGE between central incisors was high after Invisalign® extraction treatment. Orthodontic treatment planning should account for patient- and treatment-related contributing factors to mitigate OGE development, thereby optimizing aesthetic outcomes.