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. 2025 Apr 11;25(1):547.
doi: 10.1186/s12903-025-05915-5.

Risk factors for open gingival embrasures after clear aligners treatment: a retrospective study

Wenjie Cui  1 , Yibai Liu  1 , Yang Zhao  1 , Lang Lei  2 , Houxuan Li  3
Affiliations

Risk factors for open gingival embrasures after clear aligners treatment: a retrospective study

Wenjie Cui et al. BMC Oral Health. .

Abstract

Background: To explore the incidence and risk factors of open gingival embrasures (OGEs) in the front region of adult none-extraction cases with clear aligner treatment (CAT).

Methods: This retrospective study included eighty-two adult patients with non-extraction and CAT treatment, all of which were provided by Invisalign. A total of 820 tooth sites were assessed for OGEs in intraoral photographs. These sites were categorized into nonoccurrence group and occurrence group. The parameters- including crown shape, root angulation (parallel root recorded as zero and divergent root as positive), distance between cementoenamel junction, and distance from interproximal contact point (ICP) to alveolar bone crest (ABC)- were compared between occurrence group and nonoccurrence group using independent t-test and were further analyzed based on the severity. Logistic regression analysis was used to determine the significant risk factors of OGEs.

Results: The overall incidence of OGEs was 13.4% in the maxilla and 30.7% in the mandible. The highest incidence was found between the mandibular central incisors, reaching 39.02%. Age (Maxilla: OR = 1.119, 95%CI (1.048-1.195); Mandible: OR = 1.068, 95%CI (1.018-1.121), mandibular crowding (OR = 0.846, 95%CI (0.729-0.981), distance between adjacent maxillary teeth at the cementoenamel junction (Maxilla: OR = 2.400, 95%CI (1.146-5.027) and distance from ICP to ABC (Maxilla: OR = 8.046, 95%CI (4.016-16.122); Mandible: OR = 3.475, 95%CI (2.390-5.052) in the maxilla and mandible have significant correlation with the occurrence of OGEs (P<0.05).

Conclusions: OGE is a common complication after CAT, adversely affecting the smiling aesthetics. Clinicians should be well aware of risk factors, such as age, degree of dental crowding, and the distance from the ICP to ABC.

Keywords: Black triangles; Clear aligners; Open gingival embrasures; Orthodontic treatment.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: All experiments in this study were conducted in accordance with the Helsinki Declaration. This retrospective study was approved by the Ethical Committee of Nanjing Stomatological Hospital, Affiliated Hospital of Medical School, Institute of Stomatology, Nanjing University, Nanjing, China (NJSH-2023NL-036). Informed consent for the anonymous use of patient data was obtained from all individual participants included in the study. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests. Disclosure statement: The authors report there are no competing interests to declare.

Figures

Fig. 1
Fig. 1
Classification of the OGEs incidence and severity. Open gingival embrasures were classified according to severity. Line a, a tangent line to the highest gingival curvature of the crown. Line b, a line that passed through the most cervical contact point and was parallel to line (a) Line c, a line that bisected the distance between line a and line (b) The severity of the open gingival embrasures (normal, mild, moderate, severe) was determined according to the position of the tip of each gingival papilla in the anterior dental region
Fig. 2
Fig. 2
Measurement of the distance between cementoenamel junction (CEJ)
Fig. 3
Fig. 3
Measurement of root angulation and distance from interproximal contact point to alveolar bone crest
Fig. 4
Fig. 4
Measurement of the crown ratio. CW crown width, CL crown length
See this image and copyright information in PMC

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