Open gingival embrasures after orthodontic treatment in adults: prevalence and etiology.

The purposes of this study were to determine the prevalence of posttreatment open gingival embrasures in adult orthodontic patients and to examine the association of pretreatment maxillary incisor malalignment, posttreatment alveolar bone height, interproximal contact position, root angulation, crown shape, and embrasure area with open gingival embrasures. Posttreatment intraoral photographs of 337 adult orthodontic patients were evaluated to determine the prevalence of open gingival embrasures. A subsample of 119 patients was identified for measurement and divided into 2 groups: normal gingival embrasures and open gingival embrasures. Digital images of the pretreatment maxillary models and posttreatment maxillary central incisor periapical radiographs were made to measure the pretreatment and posttreatment variables. The prevalence of posttreatment open gingival embrasures in adult orthodontic patients was 38%. Pretreatment maxillary central incisor rotation and overlap were not statistically associated with posttreatment open gingival embrasures. A posttreatment alveolar bone-interproximal contact distance greater than 5.5 mm was associated with open gingival embrasures. Short and more incisally positioned posttreatment interproximal contacts were associated with open gingival embrasures. Open gingival embrasures were found to have more divergent root angulations and more divergent or triangular-shaped crown forms than normal gingival embrasures. Embrasure areas larger than 5.09 mm(2) were also correlated with open gingival embrasures. Increased alveolar bone-interproximal contact distance and increased root angulation demonstrated the greatest increase in the odds of an association with an open gingival embrasure. This investigation indicates that open gingival embrasures are common in adults who have undergone orthodontic treatment and that posttreatment variables are significant factors in open gingival embrasures.