Risk factors associated with open gingival embrasures after orthodontic treatment

Abstract

Objectives: To investigate the incidence of and contributing factors to open gingival embrasures between the central incisors after orthodontic treatment.

Materials and methods: One hundred posttreatment patients (29 men and 71 women; mean age, 24.7 years) were divided retrospectively into occurrence and nonoccurrence groups based on intraoral photographs. Based on the severity, the occurrence group was further divided into mild, moderate, and severe groups. Parameters from periapical radiographs, superimposed lateral cephalograms, and study models were compared between the occurrence and the nonoccurrence groups by using independent t-tests and were also analyzed on the basis of severity via analysis of variance. Logistic regression analysis was performed to identify the contributing factors to open gingival embrasures.

Results: The incidence of open gingival embrasures between the central incisors was 22% and 36% in the maxilla and the mandible, respectively. Lingual movement of the incisors, distance from the contact point to the alveolar crest after treatment, antero-posterior overlap of the two central incisors before treatment in the maxilla, and distance from the contact point to the alveolar crest after treatment in the mandible were significantly associated with the occurrence of open gingival embrasures ( P < .05). In the mandible, the amount of intrusion was significantly related to severity ( P < .05).

Conclusions: The incidence of open gingival embrasures following orthodontic tooth movement is high. Therefore, attention should be paid to the contributing factors to prevent or reduce the occurrence of open gingival embrasures.

Keywords: Black triangle; Open gingival embrasure; Orthodontic treatment.

Figure 1.

Classification of open gingival embrasures according to severity. Two lines parallel to the reference line (tangent line to the highest gingival curvature of the crown) were constructed: a line passing through the most cervical contact point and a line bisecting the distance between the reference line and the contact point line. According to the position of the incisive papilla tip in the four areas constructed by the three parallel lines, the severity of the groups (normal, mild, moderate, and severe) was determined.

Figure 2.

Superimposition of lateral cephalograms shows measurements of tooth movement. SN indicates Sella-Nasion; U1, the maxillary central incisor; L1, the mandibular central incisor; IMPA, incisor mandibular plane angle. Positive values denote extrusive and labial movements, while negative values denote intrusive and lingual movements. Δ U1 to SN and Δ IMPA refer to the changes in measurements between before (T1) and after (T2) treatment (Δ = T2 – T1).

Figure 3.

Periapical radiographic measurements. CEJ indicates cementoenamel junction; ABC, alveolar bone crest; ICP, interproximal contact point; a, perpendicular distance from the mesial ICP to the tooth long axis; b, perpendicular distance from the mesial CEJ to the tooth long axis.

Figure 4.

Measurements of the antero-posterior and transverse overlap of the two central incisors.

Figure 5.

Measurement of the angle formed by the incisal edges of the two central incisors.